'Functional Components in Peanuts

PLEASE SCROLL DOWN FOR ARTICLE

This article was downloaded by: [Consortium for e-Resources in Agriculture]On: 3 March 2011Access details: Access Details: [subscription number 923464531]Publisher Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

Critical Reviews in Food Science and NutritionPublication details, including instructions for authors and subscription information:http://www.informaworld.com/smpp/title~content=t713606380

Functional Components in PeanutsMaria Leonora D. L. Franciscoa; A. V. A. Resurrecciona

a Department of Food Science and Technology, The University of Georgia, Griffin, GA, USA

To cite this Article Francisco, Maria Leonora D. L. and Resurreccion, A. V. A.(2008) 'Functional Components in Peanuts',Critical Reviews in Food Science and Nutrition, 48: 8, 715 — 746To link to this Article: DOI: 10.1080/10408390701640718URL: http://dx.doi.org/10.1080/10408390701640718

Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf

This article may be used for research, teaching and private study purposes. Any substantial orsystematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply ordistribution in any form to anyone is expressly forbidden.

The publisher does not give any warranty express or implied or make any representation that the contentswill be complete or accurate or up to date. The accuracy of any instructions, formulae and drug dosesshould be independently verified with primary sources. The publisher shall not be liable for any loss,actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directlyor indirectly in connection with or arising out of the use of this material.

http://www.informaworld.com/smpp/title~content=t713606380

http://dx.doi.org/10.1080/10408390701640718

http://www.informaworld.com/terms-and-conditions-of-access.pdf

Critical Reviews in Food Science and Nutrition, 48:715–746 (2008)Copyright C©© Taylor and Francis Group, LLCISSN: 1040-8398DOI: 10.1080/10408390701640718

Functional Components in Peanuts

MARIA LEONORA D.L. FRANCISCO and A.V.A. RESURRECCIONDepartment of Food Science and Technology, The University of Georgia, Griffin 30223 GA USA

Peanut is one of the most widely used legumes due to its nutrition and taste. The fact that is has been recognized recently as afunctional food, its evaluation for its role in a heart-healthy diet has received tremendous attention. Functional compoundshave been isolated, identified, quantified, and even enhanced to maximize the amount for adequate health benefits. The peanutindustry’s byproducts such as peanut hulls and shells, skins, and even leaves and roots have also been identified as possiblesources of bioactive compounds. New uses for these underutilized renewable sources can create new market opportunitiesand increase the value of agricultural residues.

Keywords peanuts, Arachis hypogaea, functional foods, flavonoids, phenolic acids, plant sterols, stilbenes, antioxidants

INTRODUCTION

The relation between diet and health has increased the de-mand of consumers for more information about functional foods.Scientific research conducted during the past several years indi-cates that many potential health benefits from food componentsbeyond basic nutrition exist (IFIC, 2004). The beneficial com-pounds in functional foods have been called by various termssuch as phytochemicals, functional, and bioactive components.These substances exert their effects in human health by acting asantioxidants (Chun et al., 2005), activating liver detoxificationenzymes (Percival, 1997), blocking the activity of bacterial andviral toxins (Moure et al., 2001), reducing cholesterol absorp-tion (Kris – Etherton et al., 2002) or inhibiting platelet aggre-gation (Pignatelli; et al., 2000). At least 120 naturally occurringfoods have been identified as containing functional components(Pennington, 2002) and this number is expected to increase asthe search for new or alternative food sources have become amajor research interest.

Peanuts have recently attracted attention as a functional food.In the past, peanuts were perceived as an unhealthy food be-cause of their high fat content, as much as 50% w/w. At present,peanuts shifted their image from being an energy dense food toa beneficial food for long-term health as evidenced by the nu-merous beneficial components found in peanuts such as vitaminE, copper, magnesium, flavonoids, and others. The evaluation oftheir role in a heart-healthy diet has increased in the last decade(Kris – Etherton et al., 1999). Clinical studies on the consump-tion of peanuts and tree nuts demonstrated beneficial effects on

Address correspondence to A.V.A. Resurreccion, Department of Food Sci-ence and Technology, 1109 Experiment street Griffin, GA 30223 – 1797 Tel:770 – 412 – 4736 Fax: 770 – 412 – 4748. E-mail: [email protected]

plasma lipids and lipoproteins such as reduced total cholesteroland low density lipoprotein cholesterol and triglycerides withoutreducing high density lipoprotein cholesterol. The health bene-fits associated with peanuts are a reflection of their nutritionalprofile (Griel et al., 2004) including their nutrient density, fattyacid profile, and the presence of bioactive compounds. It hasbeen proven that peanuts and tree nuts are low in saturated fattyacids and high in monounsaturated and polyunsaturated fattyacids. The presence of bioactive compounds in peanuts and nutsthat elicit positive healthful effects have been identified as plantproteins, dietary fiber, micronutrients, plant sterols, and phy-tochemicals (Kris – Etherton et al., 1999). A listing of thesecompounds is given in Table 1.

There are about five large epidemiological studies that lookedat the effect of frequent nut consumption (nuts are definedas almonds, Brazil nuts, cashews, hazelnuts, macadamia nuts,pecans, pistachios, walnuts, and legume peanuts) on the riskof coronary and ischemic heart disease. These studies were theAdventist Health study, the Iowa Women’s Health study, theNurses’ Health Study, the Cholesterol and Recurrent Eventsstudy and the Physician’s Health study (Kris – Etherton et al.,2001). The Adventist Health study (Fraser et al., 1992) showedthat subjects who consumed nuts more than four times a weekexperienced substantially fewer definite fatal coronary heart dis-ease events and definite non-fatal myocardial infarctions. TheNurses’ Health study showed that women who ate more thanfive units of nuts (one unit = 1 oz of nuts) a week had a signifi-cantly lower risk of total coronary heart disease than women whonever ate nuts or who ate less than one unit a month (Hu et al.,1998). Similarly, the Physicians’ Health study suggests that nutconsumption is associated with a reduced risk of total and sud-den cardiac death (Albert et al., 2002). Studies confirming thatnuts contain several cardio-protective constituents are lacking.

715

Downloaded By: [Consortium for e-Resources in Agriculture] At: 10:06 3 March 2011

716 M.L.D.L. FRANCISCO AND A.V.A. RESURRECCION

Table 1 Beneficial components present in peanuts (value per 100 g peanuts)(USDA Nutrient Database for standard reference, Release 19; Awad et al.,2000; Gu et al., 2004; Talcott et al., 2005a; Sobolev and Cole, 1999; USDADatabase for the flavonoid content of selected foods, Release 2.1; Chukwumahet al., 2007).

Component Product description Unit Amount

Dietary fiber All types, roasted, no salt g 8.00Total monounsaturated g 24.64

fatty acidsTotal polyunsaturated g 15.69

fatty acidsVitamin E (α-tocopherol) mg 6.93Folate mcg 145.00Magnesium mg 176.00Potassium mg 658.00Calcium mg 54.00Total phytosterols Runner, dry roasted mg 60.70β-sitosterol mg 47.20Campesterol mg 5.80Stigmasterol mg 7.70Total proanthocyanidins Roasted mg 15.60p-Coumaric acid Georgia Green, raw, mg 8.82

normal-oleic(-)-Epigallocatechin All types, oil-roasted, mg 0.66

with salttrans-Resveratrol Florunner, roasted mcg 5.50Biochanin A Runner, raw, defatted mg 0.13Daidzein mg 1.75Genistein mg 0.23

More studies are needed to confirm the presence of these com-pounds and quantify the amounts needed to achieve beneficialeffects. Nevertheless, available data show that peanuts and nutshave the potential to contribute significantly to human health(Higgs, 2003).

Several bioactive compounds function as antioxidants. An-tioxidants are only one of the food components that help preventthe production of undesirable or unstable compounds that causecellular damage. Some bioactive components, but not all, func-tion as antioxidants. Growing knowledge about the health pro-moting impact of antioxidants in everyday foods, combined withthe assumption that a number of common synthetic preservativesmay have hazardous effects, has led to multiple investigationsin the field of natural antioxidants (Peschel et al., 2006).

Because of the growing concern for the potential health haz-ards of synthetic antioxidants such as butylated hydroxyanisole(BHA), butylated hydroxytoluene (BHT), and propyl gallate(PG), several authors are researching the risk of these antiox-idants to humans when used in foods. Thus, there is renewedinterest in the increased use of naturally occurring antioxidants(Nepote et al., 2004b). The replacement of synthetic antioxidantsby natural ones may have benefits due to health implications andfunctionality, however, some of them such as those from spicesand herbs have limited applications despite their high antioxi-dant activity, as they impart a characteristic herb flavor to thefood.

Plant phenolics have primary antioxidant activity. Primaryantioxidants terminate the free radical chain reaction by donating

hydrogen or electrons to free radicals and converting them tomore stable products (Rajalakshmi and Narsimhan, 1996) andare a potential source of natural antioxidants. The commercialdevelopment of plants as sources of antioxidants can be usedto enhance the properties of foods for both nutritional purposesand for preservation. Crude extracts of fruits, herbs, vegetables,cereals, nuts, and other plant materials rich in phenolics areincreasingly of interest in the food industry (Rice-Evans et al.,1997; Sang et al., 2002) for their antioxidant activity.

Within the antioxidant literature, studies dealing with resid-ual sources have been augmented considerably, which is causedby a value adding recycling interest of the agro- and food in-dustry (Peschel et al., 2006). Recycling of by-products has beensupported by the fact that polyphenols have been located specifi-cally in the peels, seeds, and hulls (Lee et al., 2003; Duh and Yen,1997; Lu and Foo, 1999; Yamaguchi et al., 1999). Seeds of plantsusually contain effective antioxidants in or around their germsto retain germination ability for long-term preservation. Whilethe leaves and barks are usually exposed to sunlight and oxygen,so they are also potential sources of antioxidants (Namiki et al.,1993). The volume and diversity of agricultural byproducts rep-resent an enormous and underutilized renewable resource, whichcan create an adverse impact in the economy and environmentthrough disposal. Byproducts may contain numerous bioactivecompounds such as vitamins, phenolics, antioxidants, carotenes,glucosinolates, soluble fiber, and other components beneficialto human and animal health, as well as materials potentiallyuseful for manufacturing bio-based products (USDA – ARS,2003).

The aim of this review is to present general aspects onbioactive components isolated and determined from peanuts,peanut products, and byproducts. The paper will focus on thepresent knowledge on the different compounds, their chemi-cal structure, and natural occurrence in peanuts and compara-ble sources of functional components, and the evidence for aprotective effect against diseases and functionality as a foodingredient. Additional information on extraction and analy-sis, processing effects, and food product application are alsoincluded.

FLAVONOIDS

Chemistry and Properties

Flavonoids are a class of secondary plant phenolics, ubiqui-tously distributed in the leaves, seeds, bark, and flowers of plants.They constitute a relatively diverse family of aromatic moleculesthat are derived from phenylalanine (Havsteen, 2002) as shownin Fig. 1. It takes different, but related courses, depending on thekind of flavonoid that is required. Over 4,000 flavonoids havebeen identified to date. These compounds play many differentroles in the ecology of plants. Due to their attractive colors,they may act as visual signals for pollinating insects. Because oftheir astringency, the flavonoids can represent a defense system


FUNCTIONAL COMPONENTS IN PEANUTS 717

O

NH2

O

O

OH

OH

O

O

O

OH

OOH

OH O

OH

OH

O+

OH

OH

OH

OH

OOH

OH O

OH

OH

OH

OH OOH

OH O

OH

OH

OH

OOH

OH

OH

OH

OH

O+

OH

OH

OH

OH

Phenylalanine to Chalcone

Naringenin chalcone

Naringenin (flavanones)

Isoflavanone derivatives

Apigenin (flavone)

Naringeninderivatives

Vitexinderivatives

Apigenin derivatives

Aromadendrin dihydrokaemfero

Leucopelargonidin(flavan-3, 4-diol) Anthocyanidins

Taxifolin dihydroquercetin

Myricetinbiosynthesis

Quercetin (flavonols)Quercetincatabolism

Kaempferolbiosynthesis

(+)-catechin(flavan-3-ol)

Anthocyanidins

Leucocyanidin (flavan-3, 4-diol)

Figure 1 Schematic diagram of the major branch pathways of flavonoid biosynthesis.

against harmful insects. Other relevant roles of flavonoids inplants are listed in Table 2.

Flavonoids are benzo-γ -pyrone derivatives (Heim et al.,2002) consisting of three phenolic rings A, B, and C (Fig. 2).The benzene ring A is condensed with a six-member ring C,which carries a phenyl benzene ring B as a substituent in the2-position. Ring C may be a heterocyclic pyran or pyrone (Ah-erne and O’ Brien, 2002). Flavonoids can be categorized intoseveral classes based on the saturation level and pattern of sub-stitution of the C ring. These are: anthocyanidins, anthocyanides,

flavonols, isoflavonols, flavones, isoflavones, flavanones, isofla-vanones, flavanols, isoflavanols, flavanes, isoflavones, auronesand, coumarins (Havsteen, 2002). Individual compounds withina class differ in the pattern of substitution of the A and B rings(Pietta, 2000). Figure 3 shows some of the flavonoids with theirstructures.

The chemical nature of the flavonoids depends on the struc-tural class, degree of hydroxylation, degree of methoxylation,other substitutions such as glycosidic side groups, and conjuga-tions between the A and B rings. Hydroxyl groups are involved



Table 2 Role of flavonoids in plants (Havsteen, 2002; Heim et al., 2002; Pietta, 2000; Drewnowski andGomez-Carneros, 2000).

Characteristic Mechanism of Action

Antioxidant Scavenge reactive oxygen species produced by the photosynthetic electron transport chainNatural pesticide Protects plants against parasites and predatorsAntimicrobial agent Inhibits/kills bacteria, pathogenic protozoansCatalyst Hastens light phase photosynthesis; regulates iron channels involved in phosphorylationVisual attractor Attracts pollinating insectsFeeding repellant Inherent astringent compounds defend plants against harmful insectsLight screen Screens UV radiation of sun and scavenge UV-generated reactive oxygen speciesGrowth inhibitor Inhibits exocytosis of auxin indolyl acetic acid; induces gene expression

during metabolism, transformed either as methylated, sulfated,or glucuronidated. In foods, flavonoids exist primarily as 3-O-glycosides and polymers. The common glycosidic units areglucose, galactose, arabinose, rhamnose, and glucorhamnose.Several types of higher structure exist, and polymers comprisea substantial fraction of dietary flavonoid intake (Heim et al.,2002).

In plants, flavonoids are relatively resistant to heat, oxygen,dryness, and moderate degrees of acidity, but can be modifiedby light. The nature of the hydroxyl group attached to the C-3of ring C affects the photostability of the flavonoid molecule(Aherne and O’Brien, 2002). Flavonoids exhibit a wide range ofproperties such as pigments and flavor compounds, dependingon their particular structures. Some compounds are extremelypotent odorants (e.g. vanillin and eugenol), but the major fla-vors associated with flavonoids are bitterness and astringency(Cheynier, 2005). Astringency, defined as a drying or puckeringmouth feel detectable throughout the oral cavity, is due to a com-plexing reaction between dietary polyphenols and proteins of themouth and saliva (Drewnowski and Gomez – Carneros, 2000).

Flavanols

Flavanols are also referred to as flavan-3-ols or catechins.Based on structure (Fig. 3), they lack the 2,3-double bondand the 4-one structure (Rice–Evans et al., 1997). The pre-dominating flavanols are (+)-catechin and (+)-gallocatechin,(−)-epicatechin, (+)-epicatechin, (−)-epigallocatechin, andthe following gallic esters: (−)-epicatechin gallate and (−)-epigallocatechin gallate (Fig. 4).

Oligomers or polymers of flavan-3-ols, also called as proan-thocyanidins or condensed tannins, are the second most abun-

O

A C

B1

2

345

6

7

8 1’

2’

3’

4’

5’

6’

Figure 2 Nuclear structure of flavonoids.

dant natural phenolics. The size of the proanthocyanidinmolecule is described by the degree of polymerization (DP). Theunits are linked mainly through C4→C8 bond, but the C4→C6linkage also exists. These linkages are called B-type linkages.An A-type linkage also exists where an additional ether bond be-tween C2→C7 results in double linkage of the flavan-3-ol units(Rasmussen et al., 2005). Proanthocyanidins consisting exclu-sively of (epi)-catechin are designated as procyanidins whilethose containing (epi)-afzelecin or (epi)-gallocatechin as sub-units are named propelargonidin or prodelphinidin, respectively.Procyanidins exist most widely in plants. Propelargonidin andprodelphinidin are less common in nature (Gu et al., 2003).Structures of proanthocyanidins are presented in Fig. 5.

Flavones and Flavonols

Flavones and flavonols have similar C-ring structures with adouble bond at the 2-3 position, with the former lacking a hy-droxyl group at the 3-position (Hollman and Arts, 2000). Majorflavones in plants are luteolin and apigenin while major flavonolsare quercetin, kaempferol, myricetin, and isorhamnetin (Fig. 6).

Flavanones and Flavanonols

Flavanones and flavanonols are minor flavonoids having asaturated C-ring. Naturally occurring flavanones have the 2Sconfiguration while the flavanonols are usually 2R:3R, with afew having the 2S:3S or 2R:3S stereochemistry. Flavanones areslightly soluble, easily converted to isomeric chalcones in alka-line media, and have the tendency to separate first in fractionalcrystallization and are easily precipitated at low pH and low tem-perature. These precipitates remain insoluble in water, methanol,ethanol, or acetone and mixtures thereof (Tomas-Barberan andClifford, 2000b). Major flavanones are eriodictyol, hesper-itin, and naringenin (Fig. 7). The most popular flavanonol istaxifolin.

Isoflavones/Isoflavonoids

Isoflavones are intrinsic plant compounds having a 1,2-diarylpropane structure. Structurally, they are well defined andto date, over 60 members of the class have been identified.Isoflavones are present in plant foods either as the aglycone



Flavanol Flavone Flavonol

Flavanone Isoflavone Flavanonol

O

56

7

2’

3’

O

O5

6

7

3

2O

OH

O5

6

7 2

O

O

7

6

5

3

2

O

O5

7

6

O

OH

O5

6

7 2

Flavanol Flavone Flavonol

Flavanone Isoflavone Flavanonol

O

56

7O

OH

23

456

7

8 1’

6’5’

4’

O

O5

6

7

3

2

O

O5

6

7

8

3

2

1’

2’

3’

4’

5’

6’

O

OH

O5

6

7 2O

OH

O5

6

78

2

1’

2’

3’

6’5’

4’

O

O

7

6

5

3

2

O

O

7

6

5

8

3

2

1’

6’

2’

3’

4’

5’

O

O5

7

6

O

O

2

5

8

7

62’

3’

4’

5’

6’

O

OH

O5

6

7 2

O

OH

O5

6

7

8

2

1’

2’

3’

4’

5’6’

Figure 3 Chemical structures of the flavonoid family.

OOH

OH

OH

OH

OH

R

OOH

OH

R2

OH

OH

R

OH

OH

OH

O

CH3

Catechins

Gallate

Epicatechins

(+)-Catechin R = H(+)-Gallocatechin R = OH

Epicatechin R = H R2 = HEpigallocatehin R = OH R2 = HEpicatechin-3-gallate R = H R2 = GallateEpigallocatechin-3-gallate R = OH R2 = Gallate

OOH

OH

OH

OH

OH

R

OOH

OH

R2

OH

OH

R

OH

OH

OH

O

CH3

Catechins

Gallate

Epicatechins

(+)-Catechin R = H(+)-Gallocatechin R = OH

Epicatechin R = H R2 = HEpigallocatehin R = OH R2 = HEpicatechin-3-gallate R = H R2 = GallateEpigallocatechin-3-gallate R = OH R2 = Gallate

Substitution pattern

Substitution pattern

Figure 4 Basic structure of catechins, epicatechins, and gallate.



O

R1

R2

R3

OH

OH

H

R5

R4

OH

OH

OH

R2

R1

OH

OH

O

OH

OH

H

R4

R3

OH

OH

OH

OH

O

OH

OH

O

H

OH

H

OH

OH

OH

O

OH

Flavan-3-ols

A-type

B-type

O

R1

R2

R3

OH

OH

H

R5

R4

OH

OH

OH

R2

R1

OH

OH

O

OH

OH

H

R4

R3

OH

OH

OH

OH

O

OH

OH

O

H

OH

H

OH

OH

OH

O

OH

Flavan-3-ols

A-type

B-type

Figure 5 Basic structures of proanthocyanidins.

(genistein or daidzein) or as different glycosides, includingacetyl and malonyl glycosides and the β-glucosides of genisteinand daidzein (Fig. 8). Among the flavonoids, isoflavones areconsidered phytoestrogens or plant derived estrogens. These arestructurally similar to the mammalian oestrogen oestradiol-17β

and exhibit oestrogenicity. The overall structure of isoflavonephytoestrogens is relatively rigid, with rotation possible onlyaround the phenolic isoflavone bond (Cassidy et al., 2000).

O

O

A C

B8

5

3

27

6

O

O

OH5

6

7

8

A C

B

2

Flavone

Substitution patternApigenin 5, 7, - OHLuteolin 5, 7, , - OH

Substitution patternQuercetin 5, 7, , - OHKaempferol 5, 7, 4’ - OHMyricetin 5, 7, 3’, 4’, - OH

O

O

A C

B8

5

3

27

6

O

O

A C

B8

5

3

2

1’

2’

3’

4’

5’

6’7

6

O

O

OH5

6

7

8

A C

B

2

O

O

OH

6’

5’

4’2’

5

6

7

8

3’

1’

A C

B

2

Flavone

FlavonolFlavonol

Substitution patternApigenin 5, 7, 4’ - OHLuteolin 5, 7, 3’, 4’ - OH

Substitution patternQuercetin 5, 7, 3’, 4’ OHKaempferol 5, 7, - OHMyricetin 5, 7, , 5’ OH

Figure 6 Basic structures of flavones and flavonols.

Dietary Sources

Flavonoids in food are generally responsible for color,taste, prevention of fat oxidation, and protection of vita-mins and enzymes (Yao et al., 2004). Existence of flavonoidsin foods is highly variable both qualitatively and quantita-tively. Some flavonoids are ubiquitous, whereas others are re-stricted to specific plant families or species. Within a sin-gle species, large variations may also occur, as a result ofgenetic differences, environmental conditions, and growth or

O

O

R1

R2

R3A C

B

FlavanonesSubstitution pattern

Eriodictyol R1, R2 OH; R3 - HHesperitin R1 – OH; R2 – OMe; R3 - HNaringenin R1 – H; R2 OH; R3 - H

O

O

R1

R2

R3A C

B

FlavanonesSubstitution pattern

Eriodictyol R1, R2 – OH; R3 - HHesperitin R1 OH; R2 OMe; R3 - HNaringenin R1 H; R2 – OH; R3 - H

Figure 7 Basic structure of flavanone.



OOH

OOH

OOH

OOCH3

OOH

OOH

OH

OOH

OOCH3

OH

Daidzein Genistein

Formononetin Biochanin A

OOH

OOH

OOH

OOCH3

OOH

OOH

OH

OOH

OOCH3

OH

Daidzein Genistein

Formononetin Biochanin A

Figure 8 Structure of isoflavones.

maturation stages. Variations in concentration may also occurfrom shells/peels/skins, to seeds and to the flesh (Cheynier,2005).

Of the fourteen classes of flavonoids enumerated in the pre-vious section, comprehensive data on their contents in foodsare available only for the flavanols (quercetin, kaempferol,and myricetin), flavones (apigenin and luteolin), catechins, andproanthocyanidins (Arts and Hollman, 2005). The main dietarysources of flavonoids are fruits, beverages (fruit juice, wine,tea, coffee, chocolate, and beer) and, to a lesser extent, vegeta-bles, dry legumes, and cereals (Kroon and Williamson, 2005).Flavonoids found in animals are considered to originate fromthe plants that animals feed rather than being synthesized in situ(Yao, et al., 2004). Main sources of dietary flavonoids for eachsub-group are given in Table 3.

Quercetin is the main flavonol in the human diet, abun-dantly found in onions and tea (Yang et al., 2001). Catechinsand epicatechins are the principal components in all types ofteas, thus sometimes they are called tea catechins. Proantho-cyanidins on the other hand are widely present in fruits andberries, nuts, beans, barley, sorghum, curry, cinnamon, wine,and beers. Most of these plant-based foods contained exclusively

Table 3 Subclasses and dietary sources of flavonoids (Aherne and O’ Brien, 2002; Rasmussen et al., 2005;Hollman And Arts, 2000; Tomas-Barberan and clifford, 2000; Cassidy et al., 2000; Gu et al., 2004; Manach et al.,2004; Cornwell et al., 2004; Chukwumah et al., 2007).

Flavonoid sub-group Representative flavonoids Major food sources (amount, mg/kgor mg/L)

Flavonols Kaempferol, Myricetin, Quercetin, Rutin Onions (300), Apples (50),Broccoli (100), Tomato (430),Tea (30), Red wine (16), Kale (450)

Flavones Apigenin, Chrysin, Luteolin Parsley (1850), Celery (140)Isoflavones Daidzein, Genistein, Glycitein, Formononetin Soya beans (2210), Chick peas (36),

Peanuts (211)Flavanols Catechin, Gallocatechin, Proanthocyanidins Apples (17), Red wine (208), Green

tea (800), Black tea (500), Peanuts(160), Peanut butter (130)

Flavanones/Flavanonols Eriodictyol, Hesperitin, Naringenin, Taxifolin Citrus peel (1000), Grapefruit (650),Lemon (300)

Anthocyanins Malvidin, Pelargonidin Aubergine (7500), Blueberry (5000),Blackberry (4000)

the homogenous B-type procyanidins (Rasmussen et al., 2005).A-type proanthocyanidins was determined in curry, cinnamon,cranberry, peanut, plums, and avocado (Gu et al., 2003). Theamount of A-type proanthocyanidins was determined to be veryhigh in these foods. Curry and cinnamon had 84–90% of the totalamount of proanthocyanidins as A-type, cranberry and peanutsabout 51–65%, and plums and avocado about 29% as A-typeproanthocyanidins. Vegetables, citrus fruits, rice, and corn arenot an important source of proanthocyanidins (Rasmussen et al.,2005). Soybeans are the most significant source of isoflavones,primarily genistein and daidzein (Yang et al., 2001).

Occurrence in Peanuts

Studies showing that peanuts may reduce the risk of car-diovascular diseases have led to the investigation of flavonoidspresent in peanuts. These flavonoids are currently under investi-gation in a bid to determine their biological and pharmacologicaleffect on human physiology (Chukwumah et al., 2005).

Total flavonoid contents (both soluble and bound forms) often nuts including legume peanuts commonly consumed in theUnited States were determined by Yang et al. (2005) Walnutshad the highest flavonoid content (745 ± 93 mg/100 g), followedby pecans, peanuts, pistachios, cashews, almonds, Brazil nuts,pine nuts, macadamia nuts, and hazelnuts. Prior and Gu (2005)further investigated the proanthocyanidin content of these nutsin terms of interflavan linkage, DP, and percentage of polymerspresent, as shown in Table 4. Mazur et al. (1998) and Mazur(1998) were able to analyze the isoflavonoid content of foodlegumes, with genistein having the most amount of isoflavonepresent in peanuts (Table 5).

Surprisingly, the seeds are not the only source of flavonoids.Outer layers such as peel, shell, and hull contain a large amountof polyphenolic compounds to protect the seed. About 50 mil-lion tons of nutshells and other assorted agricultural wastes aregenerated each year. For pecans alone, the industry generatesabout 59,500 tons of shells from its harvest. The commercial



Table 4 Interflavan linkages, constituent units, DP, and concentrations of proanthocyanidins in nuts, peanuts, and peanut by-products (Priorand Gu, 2005; Yu et al., 2006; Gu et al., 2004).

Items Interflavan linkagea Constituent unitsb DP range (Average)c Total content of proanthocyanidinsd % of polymerse

Hazelnut B C∗,G 1-P (10.8) 501 64.4Pecan B C∗, G 1-P (8.2) 494 45.1Pistachios B C∗, G 1-P (9.1) 237 51.6Almond B Af, C 1-P (8.5) 184 43.6Walnut B C∗ 1-7, P(7.8) 67 29.7Peanut A, B C 1-5 (2.6) 16 0.0Cashew B C 1–2 9 0.0Peanut butter A No data 1–3 13 0.0Peanut skins:Raw A, B No data No data 645e No dataRoasted A, B No data No data 514e No data

aA denotes A-type linkage between polymers; B denotes B-type linkage between polymers. b Af, C and GC represent constituent units(epi)afzelechin, (epi)catechin, and (epi)gallocatechin. ∗ Denotes the presence of 3-O-gallate. c The “1-5” or “1-P” in column “DP values”indicated that monomers through pentamers or polymers were detected. The average DP determined by thiolysis for selected foods is presentedin parentheses. d Expressed as mg/100 g on the basis of wet weight. e Proportion of the polymers calculated based upon weight. f Expressed asmg/100 g dry sample.

value of shells alone is a measly $2.00 a ton (Suszkiw, 1999).But a growing number of studies have been looking at shells aspossible source of antioxidants.

One of the earliest studies on shells was done by Pendseet al. (1973) The report highlighted the isolation of 5,7-dihydroxychromone from peanut shells, but eriodictyol and lu-teolin were also eluted from the acetone extract of powderedpeanut shells. Daigle et al. (1988) also found that during the im-mature stage of peanut shells, eriodictyol was the predominantflavonoid, while luteolin was the most predominant in shellsfrom mature peanuts. The antioxidative properties of peanuthulls were extensively studied only in the 1990s (Duh and Yen,1995; 1997; Yen and Duh, 1993; 1994; Yen et al., 1993). Luteolinwas the principal antioxidative component from the methanolicextracts of peanut hulls. Further studies showed that the concen-tration of total phenolics and luteolin increased as maturity ofpeanut hulls increased (Yen et al., 1993).

Peanut testae (skins, seed coats) are an extremely low valueby-product of peanut blanching operations. Their commercialvalue is $12 to $20 per ton and their limited use is only as aminor component of cattle feed. Based on world in-shell peanutproduction of 29.1 million tons in 1999–2000 and an averageskin content of 2.6%, world production of peanut skins can be es-timated at over 750,000 tons annually (Sobolev and Cole, 2003).Peanut skins have a pink-red color and carry an astringent taste.

Table 5 Isoflavonoid content of food legumes (µg/100 g) (Mazur et al., 1978; Mazur, 1998).

Food description Coumestrol Formononetin Biochanin A Daidzein Genistein

Kidney beans 2.4 4.4 2.6 28.2 158.0White kidney beans 0.0 0.0 11.7 11.4 18.2Black-eyed peas tra 0.0 0.0 30.3 55.7Chickpeas 5.0 215.0 838.0 11.4 76.3Peanuts 0.0 6.8 6.5 49.7 82.6Peanuts ndb nd nd 58.0 64.0

a tr – present in trace amountsbnd – not detected

They are typically removed before peanut consumption or in-clusion in confectionary and snack products. In the early 1940s,these were initially thought to be toxic. But after a thorough ex-amination by Dr. Jack Masquelier, then a doctoral candidate atthe Faculty of Medicine and Pharmacy, University of Bordeaux,in France, peanut skin was found to be nontoxic, and protectsand strengthens blood vessels (Louis, 1999). The colorless ex-tract obtained was named OPC, oligomer proanthocyanidins.Current research demonstrates peanut skins to contain benefi-cial flavanols and potentially other health promoting compounds(Yu et al., 2005).

Karchesy and Hemingway (1986) reported that mature, redpeanut skins contain about 17% by weight of procyanidins,nearly 50% of which are low molecular weight oligomers. Louet al. (1999; 2001; 2004) made a comprehensive analysis ofthe water-soluble phenolic extract from peanut skins, result-ing in six A-type proanthocyanidins, including procyanidins A1

and A2 (Fig. 9), and three newly found epicatechin oligomers(Lou et al., 1999) (Fig. 9). They isolated ten compounds fromthe water-soluble fraction of peanut skins (Fig. 10), includ-ing eight flavonoids and two novel indole alkaloids, reportedfor the first time from a natural source (Lou et al., 2001). In2004, they isolated five oligomeric proanthocyanidins, B2, B3,and B4 (Fig. 11) from the water-soluble fraction and two newpolyphenols, epicatechin-(2-β-O-7,4-β-6)-[epicatechin-(4-β-



O

OH

OH

OH

OH

O

OH

OH

OH

OH

OOH

2’

3’

A C

B

D

E

F

Procyanidin A1

O

OH

OH

OH

OH

2’

3’

D

E

F

Procyanidin A2

O

OH

OH

OH

OH

2’

3’

D

E

F

Epicatechin-(2 -O-7,4 -8)-ent-epicatechin

O

OH

OH

OH

OH

OH

O

O

OH

OH

OH

OH

A C

B

D

E

F 2’

3’

Epicatechin-(2 -O-7,4 -6)-catechin

2’

3’

Epicatechin-(2 -O-7,4 -6)-ent-catechin

OOH

OH

OH

OH

D

E

F

OOH

OH

OH

OH

D

E

F 2’

3’

Epicatechin-(2 -O-7,4 -6)-ent-epicatechin

Figure 9 A-type proanthocyanidins isolated from the water-soluble fraction of peanut skins.

8)]-catechin and epicatechin-(2-β-O-7,4-β-8)-[epicatechin-(4-β-8)]-catechin-(4-α)-epicatechin, based on their spectral data(Lou et al., 2004).

Catechins, A-type and B-type procyanidins dimers, trimers,and tetramers were also detected by Yu et al. (2006) inchemically purified peanut skin aqueous and ethanol extracts.Furthermore, higher concentrations of compounds mentionedwere observed in raw peanut skins than roasted peanut skins. To-tal catechins, procyanidins dimers, trimers, and tetramers in di-rectly peeled peanut skin were 16.1, 111.29, 221.33, and 296.07

mg/100 g, respectively versus 8.79, 143.48, 157.53, and 203.91mg/100 g, respectively in roasted dry skin (Yu et al., 2006).A complete list of polyphenols obtained from peanuts, peanutproducts, and by-products by various authors is presented inTable 6.

Daily Consumption and Bioavailability

The level of intake of flavonoids from the diet is consider-ably high, as compared to those of vitamin C, E, and carotenoids



Figure 10 Flavonoids and alkaloids isolated from the water-soluble fraction of peanut skins.

(Pietta, 2000). The reports available for daily consumption offlavonoids differ in values, basically due to differences in themethods used for quantifying, limitation of compounds identi-fied, and the confusion of total phenolics with total flavonoids byinvestigators (Chun et al., 2005). The first reported average dailyintake of flavonoids in the USA in 1976 is one g/day by spec-trophotometric assay. This consisted of 16% flavonols, flavones,and flavanones; 17% anthocyanins, 20% catechins, and 45% bi-flavones. As recently established, the estimated daily intake ofpolyphenols is 1 g/day, (Kroon and Williamson, 2005; Scalbertand Williamson, 2000; Scalbert et al., 2005) where flavonoids ac-count for two-thirds of the total intake of polyphenols in the diet.

The average individual intakes of flavonols in a number ofepidemiological prospective cohort studies published so far are20 mg/day in middle-aged to older American males, 26 mg/dayin elderly Dutch men, 4 mg/day in Finnish middle-aged men andwomen, and 26 mg/day in Welsh middle-aged men (Hollman

and Arts, 2000). Mean flavonol and flavone intake of US HealthProfessionals was estimated at 20 to 22 mg/day, where quercetincontributed almost 75% for both men and women (Sampsonet al., 2002). The American daily intake of flavonoids from 14fruits and 20 vegetables commonly consumed is 103 mg catechinequivalents (Chun et al., 2005).

Dietary intake of proanthocyanidins before was largely un-known because of lack of reliable values for their content infoods. But the recent development of an analytical method forproanthocyanidins has allowed the quantification of individ-ual oligomers and polymers which the USDA National Foodand Nutrition Analysis Program have employed. Based on thedatabase and food consumption data (USDA Database for theProanthocyanidin Content of Selected Foods, 2004), it has beenshown that proanthocyanidins account for a major fraction offlavonoids ingested in the US diet. Infants, children, and olderpeople appear to ingest more proanthocyanidins than adults



OOH

OH

OH

OH

OH

O

O

OH

OH

OH

OH

O O

OH OH OH

OH

OH

OH

OH

OH

OH

OH

Epicatechin-(2 -O-7,4 -8)-epicatechin-(4 -8)-catechin-(4 -8)-epicatechin

A C

B

D

F

E

H K

I

G

L

J

OOH

OH

OH

OH

OH

O

OH

OH

OH

OH

OH

O

OH

OH

OH

O

OH

Epicatechin-(2 -O-7,4 -6)-[epicatechin-(4 -8)]-catechin

A C

B

D

F

G

I

H

E

O

OH

OH

OH

OH

OH

CH3OH

Procyanidin B3

D F

E

2

3

2’

3’

O

O

OH

OH

OH

OH

OH

OH

OH

OH

OH

Procyanidin B2A C

B

D F

E

2

3

2’

3’

O

OH

OH

OH

OH

OH

CH3OH

Procyanidin B4

D F

E

2

3

2’

3’

Figure 11 Oligomeric proanthocyanidins isolated from the water-soluble fraction of peanut skins.

on the basis of body weight. The 2- to 5-yr old age groupconsumes more proanthocyanidins daily than other groups be-cause they consume more fruit. Gu et al. (2004) estimated thatthe daily intake of proanthocyanidins in the US was about 53mg/day excluding the monomers, and 57.7 mg/day including themonomers. The distribution between the intake of monomers,dimers, and trimers was found to be almost equal with an in-take of 4.1–6.4 mg/day for each group, whereas the intakeof oligomers (4–10-mers) and polymers (>10-mers) was botharound 20 mg/day. Thus, of the estimated total daily intake ofproanthocyanidins, about 73% had a DP>3.

One of the objectives of bioavailability studies is to deter-mine, among the hundreds of dietary polyphenols, which are bet-

ter absorbed and which lead to the formation of active metabo-lites. With the occurrence of over 4,000 flavonoids, bioavailabil-ity differs greatly between the various flavonoids, and the mostabundant flavonoids in the diet are not necessarily those thathave the best bioavailability profile (Manach et al., 2005).

A review of 97 bioavailability studies of polyphenols in hu-mans shows that among the flavonoids, isoflavones are the mostwell-absorbed, followed by catechins, flavanones, and quercetinglucosides, but with different kinetics. The least well-absorbedpolyphenols are the proanthocyanidins, the galloylated tea cat-echins, and the anthocyanins (Manach et al., 2005).

The proanthocyanidins found in food cover a wide rangeof DP as shown in Table 4. The concentration of monomers,



Table 6 Polyphenols isolated from peanuts and peanut products.

Raw material Compound Reference

Peanut kernels Resveratrol Rudolf and Resurreccion, 2006; 2007Dihydroquercetin Pratt and Miller, 1984p-Hydroxybenzoic acid Talcott et al., 2005ap-Coumaric acid

Peanut hulls Luteolin Yen et al., 1993; Daigle et al., 1988;Pendse et al., 1973

Eriodictyol Daigle et al., 1988; Pendse et al., 19735,7-dihydroxychromone Pendse et al., 1973

Peanut flour p-Hydroxybenzoic acid Dabrowski and Sosulski, 1984trans-p-Coumaric acidtrans-Ferulic acidtrans-Caffeic acidtrans-Sinapic acid

Peanut skins Trans-resveratrol Nepote et al., 2004bProcyanidin dimer A1 Verstraeten et al., 2005Procyanidin dimer A2

Procyanidin trimer AEpicatechin-(2β →O→7,4β →6)-catechin Lou et al., 1999Epicatechin-(2β →O→7,4β →6)-ent-catechinEpicatechin-(2β →O→7,4β →6)-ent-epicatechinProanthocyanidin A1

Proanthocyanidin A2

Epicatechin-(2β →O→7,4β →8)-ent-epicatechinIsorhamnetin 3-O-[2-O-β-glucopyranosyl-6-O-α-rhamnopyranosyl]-β-glucopyranoside Lou et al., 2001Isorhamnetin 3-O-[2-O-β-xylopyranosyl-6-O-α-rhamnopyranosyl]-β-glucopyranosideQuercetin-3-O-[2-O-β-xylopyranosyl-6-O-α-rhamnopyranosyl]-β-glucopyranoside3’,5,7-trihydroxyisoflavone-4’-methoxy-3’O-β-glucopyranosideEpicatechin-(2β →O→7,4β →6)-[epicatechin-(4β →8)]-catechin Lou et al., 2004Epicatechin-(2β →O→7,4β →8)-epicatechin-(4β →8)-catechin-(4α →8)-epicatechinProcyanidin B2

Procyanidin B3

Procyanidin B4

Ethyl protocatechuate Yen et al., 2005Epicatechin-(2β →O→7,4β →8)-catechin Karchesy and Hemingway, 1986Epicatechin-(2β →O→7,4β →8)-epicatechinEpicatechin-(4β →8)-catechinChlorogenic acid Yu et al., 2005Caffeic acidCoumaric acidFerulic acidEpigallocatechinEpicatechinCatechin gallateEpicatechin gallateResveratrolProcyanidins (trimers, tetramers, pentamers, hexamers, heptamers, octamers) Lazarus et al., 1999Procyanidin monomers Yu et al., 2006A-type procyanidin dimersB-type procyanidin dimersA-type procyanidin trimersB-type procyanidin trimersA-type procyanidin tetramersB-type procyanidin tetramers

Peanut roots, leaves Resveratrol Chen et al., 2002; Chung et al., 2003

dimers, and trimers in foods is by far exceeded by the higherpolymerized proanthocyanidins. Recent studies suggest, how-ever, that only the low-molecular-weight oligomers (those hav-ing a DP ≤ 3) are entirely absorbed in the gastrointestinal tract.The permeability of a proanthocyanidin polymer with a meanDP of 6 was approximately 10 times lower, suggesting that only

monomers, dimers, and trimers are absorbed and the polymersare not. So despite their high abundance in foods, dietary proan-thocyanidins are very poorly absorbed by the body and mayonly exert local effects in the gastrointestinal tract or effectsmediated mainly by the monomeric forms (Rasmussen et al.,2005).



Health Benefits

Flavonoids are nontoxic substances that manifest a diverserange of beneficial biological activities. The action of flavonoidsin health is controlled by its chemical structure. Since thesecompounds are based on the flavan nucleus, the number, po-sitions, and types of substitutions influence flavonoid actions.The multiple hydroxyl groups of flavonoids are responsible fortheir substantial antioxidant, chelating, and prooxidant activi-ties. While methoxy groups introduce unfavorable steric effectsand increase lipophilicity and membrane partitioning. A doublebond and carbonyl function in the heterocyclic or polymeriza-tion of the nuclear structure increases activity by giving a morestable flavonoid radical through conjugation and electron de-localization (Heim et al., 2002). The degree of polymerizationalso affects the biological action of flavonoids since, and as men-tioned in the case of proanthocyanidins, their biological effectswill only make sense at low DPs.

Dietary flavonoids have been implicated with prevention ofage-related diseases including cardiovascular disease and can-cer. Many epidemiological studies have provided mixed results.A review of studies relating to the role of flavonoids as health-promoting agents is discussed below.

Antioxidant Effects

Highly reactive oxygen species, such as singlet oxygen, 1O2,the superoxide anion radical O2·−, the hydroperoxyl radical OH·,the nitrogenoxide radical NO·, and alkyl peroxyl free radicals,are regularly produced in animals and humans under physio-logical and pathological conditions (Fang et al., 2002). Accu-mulation of free radicals in the body may cause several condi-tions including the development of atherosclerosis, cancer, andcataract and destruction of B-cells and impairment of insulinaction leading to diabetes (Knekt et al., 2002).

Endogenous antioxidant defenses of the human body suchas superoxide dismutase are capable of scavenging free radicalsand repairing oxidative damages. Polyphenols acting as exoge-nous antioxidant defenses are also capable of scavenging reac-tive oxygen species through electron-donating properties, gen-erating a relatively stable phenoxyl radical (Rasmussen et al.,2005). They scavenge superoxide anion, singlet oxygen, lipidperoxy-radicals, and/or stabilizing free radicals involved in ox-idative processes through hydrogenation or complexing withoxidizing species (Ren et al., 2003).

Another antioxidant mechanism as mentioned is the chelationof metals such as iron and copper ions, which prevent their par-ticipation in Fenton-type reactions and the generation of highlyreactive hydroxyl radicals. This ability to react with metal ions,however, also enabled polyphenols to act as pro-oxidants (Yanget al., 2001).

There is a hierarchy of flavonoid and isoflavonoid antioxidantactivities that is dependent on structure and defines the relativeabilities of the compounds to scavenge free radicals as shownin Table 7. Based on the table, most of the dietary sources

Table 7 Relative total antioxidant activities of flavonoids andantioxidant vitamins (Rice-Evans et al., 1997; Kim and Lee, 2004).

Antioxidant1 Antioxidant activity

TEAC2 VCEAC3

VitaminsVitamin C 1.00 100.00Vitamin E 1.00 24.00FlavonoidsQuercetin 4.70 229.40Kaempferol 1.30 114.60Myricetin 3.10 261.80Rutin 2.40 65.80Luteolin 2.10 178.30Chrysin 1.40 24.90Apigenin 1.50 89.80(+)-Catechin 2.40 215.70(-)-Epicatechin 2.50 245.50Epigallocatechin 3.80 264.40Epigallocatechin gallate 4.80 234.90Epicatechin gallate 4.90 221.40Taxifolin 1.90 213.50Naringenin 1.50 135.10Hesperidin 1.00 12.30Eriodictyol 1.80 n.d.Genistein 2.90 128.00Genistin 1.20 32.80Biochanin A 1.20 25.60Daidzein 1.30 71.80Daidzin 1.20 31.30Formononetin 0.10 n.d.Procyanidin B2 7.58 n.d.Procyanidin B1 6.55 n.d.

1Compounds highlighted are present in peanuts.2Measured as the TEAC (Trolox equivalent antioxidant activity) –the concentration of Trolox with the equivalent antioxidant activityof a 1 mM concentration of the experimental substance.3Antioxidant activity expressed as VCEAC (Vitamin C equivalentantioxidant capacity) – the ABTS radical scavenging activity ex-pressed as mg/L vitamin C equivalents at 10 min; nd - no data.

of flavonoids have higher antioxidant activities than the wellknown antioxidants such as vitamins C and E. The activity ofan antioxidant is also determined by its reactivity as a hydrogenor electron-donating agent; the fate of the resulting antioxidant-derived radical, which is governed by its ability to stabilize anddelocalize the unpaired electron, its reactivity with other antiox-idants, and the transition metal-chelating potential (Rice-Evanset al., 1997). Studies on the free radical-scavenging propertiesof flavonoids have permitted the characterization of the majorphenolic components of naturally occurring phytochemicalsas antioxidants. The half peak reduction potential (Ep/2) hasbeen attributed as a suitable parameter for representing thescavenging activity of flavonoids. Table 8 reveals the flavonoidswith efficient scavenging properties with their correspondinghalf peak reduction potential. A flavonoid with a low value forhalf peak reduction potential (i.e. < 0.2 mV) is readily oxidiz-able and therefore a good scavenger. Note that the flavonoidswith the highest scavenging activities include those with theo-dihydroxy structure in the B ring (Rice-Evans et al., 1997).



Table 8 Hierarchy of flavonoid antioxidant activities and therelationship with reduction potentials (Rice-Evans et al., 1997; Heimet al., 2000; Pietta, 2000).

Antioxidant activity Half peak reduction potential3

Flavonoid1 (mM)2 (mV)

Quercetin 4.7 0.06Rutin 2.4 0.18Catechin 2.4 0.16Luteolin 2.1 0.18Taxifolin 1.9 0.15Naringenin 1.5 0.60Galangin 1.5 0.32Apigenin 1.5 >1.00Chrysin 1.4 >1.00Hesperitin 1.4 0.40Kaempferol 1.3 0.12

1 Compounds highlighted are present in peanuts. 2 Measured as theTEAC (Trolox equivalent antioxidant activity) – the concentration ofTrolox with the equivalent antioxidant activity of a 1 mM concentrationof the experimental substance. 3Designated Ep/2. An Ep/2 of < 0.2indicates a chemical that is readily oxidized and therefore an efficientfree radical scavenger.

Inhibition of Low Density Lipoprotein Oxidation andAtherosclerosis

Researchers have shown that atherosclerosis has an intimaterelation with oxidative modification of low density lipopro-tein (LDL). When oxidized LDL is formed, macrophage re-ceptor scavenges the oxidized LDL and then forms foam cells.Over time, cholesterol, lipoprotein, hematoblasts, connectivetissues, and calcium may deposit and form plaque in arteries.Plaque makes arteries thicker and narrower, which may lead toatherosclerosis. The best way to prevent the formation of a fattystreak of atherosclerosis at the initial stage is to suppress LDLoxidation and use of drugs to decrease hyperlipidermia (Yen,and Hsieh, 2002).

LDL oxidative modification may be suppressed by supple-menting antioxidants, such as vitamin E. It was suggested thatthe availability of flavonoids at the oxidative site on LDL mayblock oxidative attack and prevent LDL oxidation in vivo (Birtet al., 2001). The antioxidant primarily inhibits LDL perox-idation by scavenging free radicals and chelating metal ions(Yen and Hsieh, 2002).

Protection Against Cardiovascular Diseases (CVD)

The formation of stable phenoxyl radical by flavonoidsthrough its scavenging properties protects the body againstoxidation and limits the risk of developing CVD (Rasmussenet al., 2005). Of the few prospective studies in humans that havepredicted the effects of flavonoids on CVD risk, some showedan inverse association, whereas others showed no association.But overall, the evidence suggests that individuals with thehighest flavonoid intake have modestly reduced risks of CVD(Vita, 2005)

A recent review by Arts and Hollman (2005) on clinicalstudies conducted as of 2005 showed that 12 cohort studies on

flavonoid intake and the risk of coronary artery disease (CAD)and five cohort studies on the risk of stroke have been published.Seven of these prospective studies found the protective effectsof flavonols and flavones or of catechins with respect to fatalor nonfatal CAD, and reductions of mortality risk were up to65%. These studies were as follows: the Zutphen Elderly Study,the Finnish Mobile Clinic Health Examination Survey, the IowaWomen’s Health Study, the Alpha Tocopherol, Beta CaroteneCancer Prevention Study, the Dutch Zutphen Elderly Study, andthe Rotterdam Study, in the Netherlands (Arts and Hollman,2005).

Anticancer Promoting Agents

Knekt et al. (2002) estimated flavonoid intakes of 10,054 menand women mainly on the basis of the flavonoid concentrationsin Finnish foods with a dietary history method. They found thatmen with higher quercetin intakes had a lower lung cancer inci-dence (P = 0.001), and men with higher myricetin intakes hada lower prostate cancer risk (P = 0.002). The role of dietaryflavonoids in cancer prevention is widely discussed in the litera-ture. A growing number of epidemiological studies suggest thathigh flavonoid intake may be correlated with a decreased risk ofcancer.

The mechanism of action of flavonoids against cancer havebeen identified including the modulation of metabolism anddisposition of carcinogens; inhibition of cancer cell prolifera-tion, angiogenesis and activity of P-glycoproteins, disturbanceof normal cell cycle progression, and induction of apoptosis,differentiation between normal and abnormal cells, and detoxi-fication enzymes (Ren et al., 2003). In vitro studies of specificflavonoids (i.e. cucurmin, genistein, and quercetin) show thatthey affect signal transduction pathways, leading to inhibition ofcell growth and transformation, enhance apoptosis, reduced in-vasive behavior, and slower angiogenesis (Lambert et al., 2005).

Inhibition of Platelet Aggregation

Platelet aggregation is a central mechanism in the pathogen-esis of acute coronary syndromes, including myocardial infarc-tion and unstable angina. Platelet aggregation contributes to thedevelopment of atherosclerosis by several mechanisms and theinhibition of platelet aggregation is thus regarded as beneficial.There is also extensive evidence that antiplatelet therapy reducesCVD (Rasmussen et al., 2005; Vita, 2005). The beneficial effectsappeared to be related to reduced activation of protein kinase C,as reported by Freedman et al. (2001) when they examined the ef-fects of grape juice on platelet function. Several in vitro studiesshowed that flavonoids such as quercetin and catechin inhibitplatelet aggregation. Pignatelli et al. (2000) also showed thatcatechin and quercetin inhibited collagen-induced platelet ag-gregation and platelet adhesion to collagen. These data indicatethat flavonoids inhibit platelet function by blunting hydrogenperoxide production and, in turn, phospholipase C activation.In addition, specific flavonoids were found to have the ability tocompete for binding to the thromboxane A2 receptors, therefore,



antagonism of this receptor may represent an additional mech-anism for the inhibitory effect of flavonoids in platelet function(Guerrero et al., 2005).

There are quite a few studies involving the biological ef-fect of bioactive compounds isolated from peanuts. Morenoet al. (2006) assessed the effects of peanut shell extract on lipidmetabolic enzymes and evaluated its potential development forthe treatment of obesity. Animal studies showed that the actionof peanut shell extract may in part be attributed to the inhibitionof fat absorption in the digestive tract, the activation of lipidmetabolism in the liver, and the reduction of the adipocyte lipol-ysis. The bioactivity of the extract may be caused by the potenti-ating action of several compounds such as coumarin derivativesand flavonoid glycosides, making the extract a potential multi-functional botanical therapeutic for weight control.

Verstaeten et al. (2005) investigated the antioxidant actionand membrane disruption protection of procyanidin dimers andtrimers isolated from peanut skins. Results indicated positive in-teraction between the dimers and trimers with lipid membranesand thus can modulate membrane fluidity, affecting numerouscellular processes, the functionality of membrane-associated en-zymes and certain intracellular transport mechanisms and mem-brane receptors. A reduction in the ability of oxidants and otherdisturbing molecules to damage cell membranes is expectedupon absorption of procyanidins-rich foods.

PHENOLIC ACIDS


Two classes of phenolic acids can be distinguished: deriva-tives of benzoic acid and derivatives of cinnamic acid (Fig. 12).The hydroxybenzoic acid derivatives are phenolic metaboliteswith a general structure C6→C1 (Tomas-Barberan and Clifford,2000a). Hydroxybenzoic acids in both free and esterified formsare found only in a few plants eaten by humans, thus, they havenot been extensively studied and are not currently considered tobe of great nutritional interest (Manach et al., 2004).

Cinnamic acids are a series of trans-phenyl-3-propenoic acidsdiffering in their ring substitution (Clifford, 2000). The hydrox-ycinnamic acids, p-coumaric, caffeic, ferulic, and sinapic acidsare more common than hydroxybenzoic acids. These acids arerarely found in the free form, except in processed food that hadundergone freezing, sterilization, or fermentation (Manach et al.,

R3

R2

R1OH

Hydroxybenzoic acid

R1

R2

O

O

Hydroxycinnamic acid

R3

R2

R1OH

Hydroxybenzoic acid

R1

R2

O

OO

Hydroxycinnamic acid

Figure 12 Structures of phenolic acids.

2004). Hydrocinnamic acids occur in most tissues in a variety ofconjugates in esters and amide forms, whereas conjugated gly-coside rarely occurs (Karakaya, 2004). The best known conju-gate is 5-caffeolyquinic acid (chlorogenic acid), formed betweentrans-cinnamic acids and quinic acid (Clifford, 2000). Phenolicacids are potent antioxidants just like the flavonoids due to thereactivity of the phenol moiety, the primary mode of which isradical scavenging via hydrogen atom donation (Robbins, 2003).

Dietary Sources

Phenolic acids and its derivatives are abundant in food andmay account for about one third of the phenolic compounds inthe diet (Table 9). These compounds are found as esters whichare either soluble or insoluble. The most frequently encounteredhydroxycinnamic acids are caffeic acid and ferulic acid. Deriva-tives of hydroxycinnamic acid are found in almost every plant(Yang et al., 2001).

Caffeic acid, both free and esterified, is generally the mostabundant phenolic acid and represents between 75% and 100%of the total hydroxycinnamic content of most fruit. While ferulicacid is the most abundant phenolic acid found in cereal grains,which constitute its main dietary source.


The polyphenolic content of raw and dry roasted peanut sam-ples containing varying levels of oleic acid (normal, mid, andhigh) were recently determined by Talcott et al. (2005a; 2005b)Normal oleic acid peanuts had higher concentrations of indi-vidual polyphenolics than mid- and high-oleic peanuts. Freep-coumaric acid, three esterified derivatives of p-coumaric, andtwo esterified derivatives of hydrobenzoic acid were identifiedas the predominant polyphenolics. Whole raw peanuts had amean of 25 mg/kg of p-coumaric acid (from a range of 8 to66 mg/kg among cultivars) and the value increased to an aver-age of 69 mg/kg when peanuts were roasted at 175◦C for 10min. Differences in concentration among cultivars only showthat background genetics, disease resistance, growth conditions,post-harvest handling, or response to roasting conditions greatlyaffects the occurrence of polyphenols. p-coumaric acid was alsopreviously identified to be present in defatted peanut flour at aconcentration of 40–68% of the total phenolics (Seo and Morr,1985).

Huang et al. (2003) isolated and identified the ethanolic ex-tract fraction from peanut seed testa that showed the highest yieldand marked antioxidant activity. Thin layer chromatographicseparation of this fraction allowed the isolation of the antiox-idant component in peanut seed testa which was identified asethyl protocatechuate (3,4-dihydroxybenzoic acid ethyl ester).


The American daily intake of phenolics from 14 fruits and 20vegetables commonly consumed is 450 mg gallic acid equivalent



Table 9 Dietary sources of phenolic acids (Manach et al., 2004; Talcott et al., 2005; 2005; Dabrowskiand Sosulski, 1984).

Phenolic acid Representative Sources (amount, mg/kg or mg/L)

Hydroxybenzoic acids Protocatechuic acid Blackberry (270), RaspberryGallic acid (100), Black currant (130),p-Hydroxybenzoic acid Strawberry (90), Roasted

peanuts (142)Hydroxycinnamic acids Caffeic acid Blueberry (2200), Kiwi (1000),

Chlorogenic acid Cherry (1150), Plum (1150),Coumaric acid Aubergine (660), Apple (600),Ferulic acid Pear (600), Potato (190), CornSinapic acid flour (310), Cider (500), Coffee

(1750), Roasted peanuts (266), defatted peanut flour (173)

(Chun et al., 2005). A German study estimated daily consump-tion of hydrocinnamic acids, hydrobenzoic acids and caffeic acidat 211, 11, and 206 mg/day, respectively (Manach et al., 2004).Benzoic acid may be obtained from foods or as an antimicrobialadditive. Based on the World Health Organization’s Joint Ex-pert Committee on Food Additives (JECFA), an acceptable life-time daily intake (ADI) of benzoic acid of up to 5 mg/kg bodyweight was approved (Tomas-Barberan and Clifford, 2000a).Intake of hydrocinnamic acid varies widely but may be veryhigh, up to 800 mg/day among coffee drinkers (Manach et al.,2004).

Very few studies have addressed the bioavailability of hy-droxycinnamic acids compared with other polyphenols. For hy-droxybenzoic acids, very little is known about its absorption andmetabolism. However, the few studies addressing the bioavail-ability of gallic acid in humans revealed that this compoundis extremely well absorbed, compared with other polyphenols(Manach et al., 2005).

Health Benefits

In animal studies, dietary gallic and ellagic acids have shownhepatoprotective activity against carbon tetrachloride toxicity,but the doses given are well above those that might be expectedfrom normal human diets. The safety of ellagic acid at high doseshowever, remains controversial (Tomas-Barberan and Clifford,2000a). The same is true for caffeic acids. Caffeic acid at a levelof 2% in diet (which is extremely high compared to the normaldietary levels) induced forestomach and kidney tumors in ratsand mice (Hagiwara et al., 1991).

Protocatechuic acid at a concentration of 10 µg/ml showeda stronger inhibitory effect against LDL oxidative modifica-tion induced by Cu2+ than ascorbic acid at the same con-centration (Yen and Hsieh, 2002). Yen et al.’s (2005) re-view also showed that protocatechuic acid was an efficaciousagent in different tissues such as diethylnitrosamine in theliver, 4,-nitroquinoline-1-oxide in the oral cavity, azoxymethanein the colon, N-methyl-N-nitroso urea in glandular stom-ach tissue, and N-butyl-N-(4-hydroxybutyl) nitrosamine in thebladder.

PLANT STEROLS


Plant sterols are an essential component of the membranes ofall eukaryotic organisms. They are either synthesized de novoor taken up from the environment. Plant sterols are called phy-tosterols which covers plant sterols and plant stanols. Over 250different sterols and related compounds in various plant and ma-rine materials have been reported. Beta-sitosterol, campesterol,and stigmasterol are the most common plant sterols. Chemicalstructures of these sterols are similar to cholesterol, differingin the side chain. For example, sitosterol and stigmasterol havean ethyl group at C-24, and campesterol a methyl group at thesame position (Piironen et al., 2000; Ohr, 2003). They inhibit theabsorption of cholesterol in the gut, while not being absorbedthemselves in significant amounts.

Sterols in plants exist in the free form or esterified to fattyacids or as steryl glycosides (EU-SCF, 2002). Hydrogenation ofthe plant sterols results in the formation of plant stanols. They aresaturated phytosterols that are less abundant in nature but theycan be produced by 5-alpha hydrogenation of the correspondingphytosterols (e.g. sitostanol and campestanol).

Plant sterols are categorized into three: (a) 4-desmethylsterols(no methyl groups); (b) 4-monomethylsterols (one methylgroup) and; (c) 4,4-dimethylsterols (two methyl groups) (IFST,2005).

The most common plant sterols belong to the 4-desmethyl-sterols, which are structurally similar to cholesterol as shown inFig. 13.

Dietary Sources

The commonly consumed plant sterols are sitosterol, stigmas-terol, and campesterol which are predominantly supplied by veg-etable oils. Minimal amounts can be sourced from cereals, nuts,and vegetables (Piironen et al., 2000). Phytosterols are naturalcomponents of vegetable oils such as sunflower seed oil and talloil, the latter derived from the process of paper production fromwood. The proportion of plant stanols is higher in tall oil than



OH OH

OH OH

OH

Beta-sitosterol7-Avenasterol

5-Avenasterol

Stigmasterol Campesterol

OH OH

OH OH

OH

Beta-sitosterol7-Avenasterol

5-Avenasterol

Stigmasterol Campesterol

Figure 13 Structural formulae of 4-desmethylsterols.

vegetable oils. Normal refining of edible oils results in partialextraction of plant sterols together with some tocopherols. It isestimated that 2500 tons of vegetable oil needs to be refined toproduce one ton of plant sterols (IFST, 2005). Thus, phytosterolsare by-products of vegetable oil refining. Phytosterols are iso-lated from conventional edible oils (soya, maize, sunflower, andrapeseed). The conventional caustic refining procedure involvesdegumming, neutralization, bleaching, and deodorization. Thelast step, a mass-transfer process, by which substances are evap-orated from the oil under reduced pressure (2–10 mbar) andelevated temperature (230–270◦C), leads to the formation of adistillate making around 0.1–0.3% of oil mass and containing8–20 % sterols (EU-SCF, 2000).

The main sources of phytosterols in the basic diet are cookingoils and margarines. Bread and cereals can also contribute sig-nificantly to total phytosterol intake. Reduced-fat health spreadsavailable in the market contain about 0.3–0.4% phytosterols,corn oil margarines are highest in phytosterols (0.5%). Vegeta-bles and fruits contain < 0.05% (based on the edible portions),except seedlings of barley, beans, peas which contain 0.1–0.2%phytosterols. Sunflower and sesame seeds are also rich sources,

containing about 0.5–0.7% and legumes can contain 0.22% phy-tosterols (EU-SCF, 2000).


Peanuts as a source of phytosterol has been getting a lot ofattention with new research findings identifying beta-sitosterolin peanuts and peanut products as cancer growth inhibitors, aswell as protectors against heart diseases (PI, 2000). Awad et al.(2000) studied the phytosterol contents of peanuts and peanutproducts (Table 10). Results show that among the four cultivarsstudied, the Valencia peanuts in raw, dry roasted, and oil roasted,contained the highest phytosterol concentration; regular and nat-ural peanut butter contain significant amounts of phytosterols aswell as peanut flour; the peanut oil refining process, however, de-creases the amount of phytosterols in peanut oil. Refined peanutoil contains 38% more phytosterol than refined (pure) olive oil.Commercial peanut oil analyzed by Ye et al. (2000) containedmore than 200 mg total sterols/100 g. This figure is within thereported value of the USDA Nutrient Database of 207 ± 43mg/100 g of peanut oil (USDA, 2007).



Table 10 Phytosterol contents of pecans, peanuts and peanut products.

Total phytosterolsProduct (mg/100g EP) Reference

Raw, shelled, Georgia green 64–125 Koehler and Song, 2002Raw, shelled peanut ∼ 100 Ye et al., 2000Commercial peanut oil >200 Ye et al., 2000Pecans 75–95 Ye et al., 2000Raw, shelled, air-dried

Red peanuts 95.8 Awad et al., 2000Runner peanuts 63.3 Awad et al., 2000Valencia peanuts 126.9 Awad et al., 2000Virginia peanuts 55.1 Awad et al., 2000

Dry roastedRed peanuts 105.2 Awad et al., 2000Runner peanuts 60.7 Awad et al., 2000Valencia peanuts 113.5 Awad et al., 2000Virginia peanuts 75.9 Awad et al., 2000

Oil roastedRed peanuts 89.2 Awad et al., 2000Runner peanuts 61.4 Awad et al., 2000Valencia peanuts 103.8 Awad et al., 2000Virginia peanuts 61.7 Awad et al., 2000

Peanut oilUnrefined 206.8 Awad et al., 2000Refined 189.2 Awad et al., 2000Deodorized 139.1 Awad et al., 2000Hydrogenated 137.9 Awad et al., 2000

Peanut ButterNatural 143.5 Awad et al., 2000Regular 156.7 Awad et al., 2000

Peanut FlourDark roast 54.5 Awad et al., 2000Light roast 59.7 Awad et al., 2000

Changes in the phytosterol composition of the GeorgiaGreen peanut were investigated by Koehler and Song (2002).Beta-sitosterol, campesterol, stigmasterol, and avenasterol werefound in all samples of the Georgia Green peanuts at variousmaturities. The content of beta-sitosterol and stigmasterol bothincreased significantly at each degree of maturity, while campes-terol levels remain unchanged. Avenasterol levels increased onlyto the third maturity level, then declined slightly. Phytosterol lev-els in Georgia Green peanuts were found not to be dependenton the number of days between planting to harvest but are de-pendent on the maturity level of the harvested peanut kernels.Mature kernels (at the orange and brown/black maturity stages),contain significantly more total phytosterols.

Grosso and Guzman (1995) and Grosso et al. (1997; 2000)studied the sterol composition of aboriginal peanut seedsfrom Peru, Bolivia, and some wild peanut species nativeto South America. Seven 4-desmethylsterols were detectednamely: cholesterol, campesterol, stigmasterol, Beta-sitosterol,�5-avenasterol, �7-stigmasterol, and �7-avenasterol. Beta-sitosterol was the prominent sterol in the composition of allsamples from various sources followed by campesterol, stig-masterol, and �5-avenasterol.

Other nuts also contain substantial amounts of phytosterols.Oil extracted from freshly ground walnuts, almonds, hazelnuts,and macadamia nuts contain β-sitosterol, ranging in concentra-

tion from 991.2 to 2071.7 µg/g oil (Maguire et al., 2004). Beta-sitosterol was also the major sterol found in pecans. The amountfrom seven cultivars ranged from 75 to 95 mg total sterols per100 g, which is about 90% of the total. The remaining 10% con-sisted of campesterol, brassicasterol, and stigmasterol (Ye et al.,2000).


Average dietary intakes of plant sterols in Western diets arebetween 200–400 mg/day. Major sources of plant sterols in typ-ical Western diets are cooking oils, margarines, peanut butter,legumes, and some seeds (sunflower and sesame) (IFST, 2005).Asians and vegetarians on the other hand consume 345–400mg/day (Awad et al., 2000).

Approximately 250 mg of phytosterols per day (≈ 4 mg/kgbw/d) is consumed in a typical US diet. In the adult Finnishpopulation, the average intake is about 300 mg/d (≈ 5 mg/kgbw/d) with an upper limit of 680 mg/d (≈ 10 mg/kg bw/d) (EU-SCF, 2000). In the Netherlands, the total mean intake of beta-sitosterol, campestanol, and beta-sitostanol was 285 ± 97 mg/d(Normen et al., 2001). Generally the intake of adult vegetari-ans and their children is higher (up to 40%) than the averagefor the population as a whole. Infant formulae based on cow’smilk contain 0.08–0.20 mmol/L β-sitosterol, 0.03–0.10 mmol/Lcampesterol and around 0.02 mmol/L stigmasterol, while humanmilk is not a significant source of phytosterol (EU-SCF, 2000).

Health Benefits

Plant sterol and plant stanols appear to be without hazardto health, having been shown without adverse effects in a largenumber of human studies. Their low abundance in human tissuescan be explained by the fact that they are poorly absorbed, andare excreted faster from the liver than cholesterol (Kris-Etherton,2002). They show no evidence of toxicity even at high dose levelssince gastro-intestinal absorption is low (IFST, 2005). Further-more, the European Union through the Scientific Committee onFood concluded that the use of phytosterol-esters in yellow fatspreads (maximum level of 8% free phytosterols) is safe forhuman use (EU-SCF, 2000). More recently, the European FoodSafety Authority (EFSA) through its Scientific Panel on Di-etetic Products, Nutrition, and Allergies, has recommended thatsterol-containing foodstuffs should not be consumed in amountsresulting in total phytosterol intakes exceeding 3 g/day (EFSA,2003). In the USA plant sterol esters in plant oil-based spreadsat levels up to 20% are generally recognized as safe (EU-SCF,2000).

The USFDA in 2000 authorized the use of labeling healthclaims in certain foods about the role of plant sterol or stanolin reducing the risk of coronary heart disease. They workby blocking the absorption of cholesterol from the diet (Ohr,2003). Studies with sitosterol or mixtures of plant sterols haveshown that they reduce serum cholesterol levels in humans by



approximately 10%. This discovery has resulted in subsequentresearch to evaluate the effects of sitosterol derivatives on choles-terol absorption and serum cholesterol levels. The reduction intotal and LDL cholesterol is the result of a decrease in cholesterolabsorption and an alteration of enzymes involved in cholesterolmetabolism and excretion (Kris-Etherton et al., 2002).

In vivo studies have shown that the consumption of phy-tosterol inhibits the development of chemically induced coloncancer. In addition, phytosterol consumption normalized the hy-perproliferative state of rat and mouse colonocytes, where hyper-proliferation of colonic mucosa is considered to be a risk factorin the development of colon cancer. In vitro studies have shownthat beta-sitosterol, identified in peanuts and peanut products,inhibits HT-29 human colon cancer cell growth, induces apop-tosis in LNCaP human prostate cancer cell, inhibits apoptosisin MDA-MB-231 human breast cancer cells, and testosterone-metabolizing enzymes in normal rat tissues (Awad et al., 2000;1998). The relation between plant sterol intakes and colorec-tal cancer risk in the Netherlands, however, showed no clearassociation between the intake of any of the plant sterols andcolon and colorectal cancer risk for men and women, respec-tively (Normen et al., 2001). Based on extensive toxicologicaltesting of phytosterol preparations in a 13-week feeding studywith rats, in a two-generation feeding study with rats, in studieson oestrogenic potential, and in tests on genotoxicity, no safetyconcerns were apparent (EU-SCF, 2000).

STILBENES


Stilbenes contain two phenyl compounds connected by a 2-carbon methylene bridge. They occur in nature in a rather re-stricted distribution. Stilbenes like isoflavonoids, are also clas-sified as phytoestrogens. Most stilbenes in plants act as antifun-gal phytoalexins, compounds that are usually synthesized onlyin response to infection or injury. Phytoalexins possess anti-fungal activity against Aspergillus, Penicillium, and Cladospo-rium species. The most extensively studied stilbene is resvera-trol (3,5,4′-trihydroxystilbene) (Yang et al., 2001; Sobolev andHorn, 2003). Resveratrol occurs in the cis- and trans- isomers(Fig. 14). Only the trans- isomer was reported as estrogenic(Cornwell et al., 2004).

Dietary Sources

The major dietary source of phytoestrogenic stilbene isresveratrol. Resveratrol is one of the major stilbene phytoalexincompounds produced by grape berries and peanuts in responseto stress like fungal infection, the presence of heavy metal ions,or ultra-violet (UV) irradiation (Seo et al., 2005). The type ofpostharvest processing affects the final concentration of resvera-trol in the product. For example, red wines have more resveratrol

OH

OH

OH

OH OH

OH

1

2

OH

OH

OH

OH OH

OH

1

2

Figure 14 Resveratrol isomers, 1, trans-resveratrol and 2, cis-resveratrol.

than white wines since resveratrol is found in the skin (Cornwellet al., 2004).


Stilbene phytoalexins are produced by the peanut plant asa defense mechanism against exogenous stimuli like fungalinvasion. Stilbenoids found in peanut include resveratrol, 3-isopentadienyl resveratrol, and various arachidins (Ku et al.,2005). Resveratrol is present in peanuts to protect the plant fromplant pathogens (Higgs, 2003). The amount, however, is lowcompared to those of grapes. Resveratrol was found to be presentin substantial amounts in the leaves, roots, and shells of peanuts,but very little was found in developing seeds and seed coats offield-grown peanuts (Chung et al., 2003). The phytoalexin con-tent of peanuts, however, increases during germination and is en-hanced by microbial infection, postharvest induction proceduressuch as soaking and drying; wounding (slicing and incubation);UV light exposure, among others. Raw peanuts soaked in waterfor about 20 hours and dried for 66 hours increased the resvera-trol content between 45 and 65 times after the soaking treatment(Seo et al., 2005). Germination of peanut kernels (25◦C, 95%relative humidity, 9 days in the dark) increased the resveratrolsignificantly from the range of 2.3 to 4.5 µg/g up to the rangeof 11.7 to 25.7 µg/g (Wang et al., 2005). Rudolf and Resurrec-cion (2006) were also able to increase the resveratrol content ofpeanut kernels by application of abiotic stresses. Slicing (2 mm),ultrasound exposure for 4 min at 25◦C, and incubation for 36h increased the resveratrol content from 0.48 µg/g in untreatedpeanuts to 3.96 µg/g in treated peanuts.

Boiled peanuts contain more resveratrol than peanut butterand roasted peanuts. The maturity of peanuts is also a factorwhere smaller peanuts have higher levels than more maturepeanuts (Sobolev and Cole, 1999). The resveratrol contents ofpeanut butter also vary with blended peanut butters (those con-taining vegetable oils) containing more resveratrol than naturalpeanut butters (Ibern-Gomez et al., 2000).

Unequal distribution of resveratrol is found where higher lev-els are present in the seed-coat than the kernel. Seed coats from



runner and Virginia types contained approximately 0.65 µg/g ofseed coat, which is equivalent to < 0.04 µg/seed (Sanders et al.,2000). Ethanolic extract prepared from defatted peanut skinseven showed higher resveratrol contents. The ethanolic extractcontained 91.4 µg/g while the dry peanut skins contain 9.07µg/g (Nepote et al., 2004a). Pistachios were also found to con-tain resveratrol. The formation of the cis-isomer in pistachioswas found to be higher than in peanuts according to Tokusogluet al. (2005) Trans-resveratrol content and of peanuts and peanutproducts is shown in Table 11.

Another stilbenoid can be found in peanuts. Piceatannol(3,4,3′,5′-tetrahydroxy-trans-stilbene), like resveratrol, are alsosynthesized as phytoalexins. Its concentration in peanuts is lowerthan resveratrol. However, in a study conducted by Ku et al.(2005) on the production of stilbenoids from the calluses ofpeanuts, showed that the concentration increased from 2.17 to5.31 µg/g after exposure to UV irradiation for 18 hours understatic culture.


No report has been published regarding daily intake of resver-atrol by consumers. It can be assumed, however, that red winedrinkers would have more resveratrol intake than non-drinkers.Resveratrol has high bioavailability and physiological levels canbe obtained through drinking red wine (Cornwell et al., 2004).

Health Benefits

Resveratrol has been associated with reduced CVD and re-duced cancer risk. Resveratrol has been shown from in vitro,ex vivo, and animal studies to have many attributes that mayprovide protection from atherosclerosis, antiproliferative, andproapoptotic properties against breast, colon, prostatic, andleukemia cells (Higgs, 2003).

Table 11 Trans-resveratrol content in peanuts and peanut products.

Trans-resveratrolProduct content (µg/g) Reference

Roasted peanuts 0.018–0.080 Sobolev and Cole, 1999Peanut butter 0.148–0.504 Sobolev and Cole, 1999Boiled peanuts 1.779–7.092 Sobolev and Cole, 1999Spanish, raw 0.023–1.792 Sanders et al., 2000Virginia, raw 0.048–0.306 Sanders et al., 2000Runner, raw 0.039–0.069 Sanders et al., 2000Peanut butter, blended 0.265–0.671 Ibern-Gomez et al., 2000Peanut butter, natural 0.534–0.753 Ibern-Gomez et al., 2000Virginia, raw 0.100–0.250 Lee et al., 2004Spanish, raw 0.090–0.300 Lee et al., 2004Peanut butter 0.270–0.700 Lee et al., 2004Runner, raw, treated1 3.000–4.920 Rudolf and Resurreccion, 2006Runner, raw, treated2 1.050–1.380 Rudolf and Resurreccion, 2007Runner, raw 2.390–7.840 Chukwumah et al., 2007

1Raw peanuts were sliced to 2 mm, exposed to ultrasound for 4 min at 25◦C,and incubated for 36 h at 25◦C.2Raw peanuts were stressed by slicing and ultrasound and incubated at 25◦C.

There is evidence to suggest that resveratrol inhibits LDLoxidative susceptibility in vitro and platelet aggregation. Olasand Wachowicz (2002) reported that resveratrol had a protectiveeffect against reactive oxygen species production in resting andactivated blood plates. Moreover, resveratrol also reduced thedifferent step of platelet activation (platelet adhesion to collagenand fibrinogen, aggregation, secretion and eicosanoid synthesis).Resveratrol has also been shown to inhibit the expression of thetissue factor gene; tissue factor protein initiates the coagulationcascade resulting in thrombus formation. The evidence suggeststhat resveratrol may decrease CVD risk by multiple mechanisms(Kris-Etherton et al., 2002).

Stilbenes inhibit cellular events associated with tumor ini-tiation, promotion, and progression. They inhibit free radicalformation, which will inhibit tumor initiation. They act as anantimutagen since they induce the quinine reductase enzymecapable of detoxifying carcinogens. Moreover, they exhibit anti-inflammatory activity and inhibit the hydroperoxidase activity ofcyclooxygenase, thus inhibiting the arachidonic pathway lead-ing to the formation of prostaglandins that stimulate tumor cellgrowth and can activate carcinogenesis (Cassidy et al., 2000).

Resveratrol’s estrogenic activity has led investigations of itspotential use as a chemotherapeutic agent in breast cancers. Astudy conducted on human breast xenografts in vivo inducedtranscription via both ERα and ERβ, resulting in lower tu-mor growth, decreased angiogenesis, and increased apoptosis(Garvin et al., 2006).

Induction of peanuts to synthesize bioactive stilbenoids ex-hibited potent antioxidant and anti-inflammatory activities asshown by Chang et al. (2006). All peanut stilbenoids at 15µM(arachidin-1, arachidin-3, isopentadienylresveratrol) showedvaried potencies in suppressing lipopolysaccharide-induced in-flammation of mouse macrophage cells as affected by the num-ber and position of other hydroxyl groups and isopentyl orisopentadienyl moiety. Production of prostaglandin and nitricoxide was significantly inhibited by arachidin-1 (p < 0.001),resveratrol (p < 0.001), and arachidin-3 (p < 0.01),

ANALYSIS OF BIOACTIVE COMPONENTS IN PEANUTS

Extraction Methods

It has been stated that there are more than 4,000 phenoliccompounds and the number is still increasing. Most of the com-pounds that have been proven to be potent antioxidants are fromplant materials. Extraction procedures would play a big role ingetting these bioactive components since extracting solvent, iso-lation procedures, purity of active compounds, as well as the testsystem and substrate to be protected by the antioxidant affectsits function (Moure et al., 2001).

Solvent Extraction

Solvent extraction is more frequently used for isolation ofantioxidants and both the extraction yield and the antioxidant



activity of extracts are strongly dependent on the solvent, due tothe different antioxidant potential of compounds with differentpolarity (Moure et al., 2001). The extraction of polyphenols isdependent on two events, the dissolution of each polyphenoliccompound at the cellular level in the plant material matrix, andtheir diffusion in the external solvent medium (Shi et al., 2005).A list of extraction solvents used for polyphenolics is givenbelow.

Extraction by hot water. Water is a natural solvent, which doesnot leave any harmful residue behind. Infusion and decoctionare simple methods for extraction with water. The formerinvolves addition of boiling water to the material, while thelatter requires boiling the material for about 15 min in water(Silva et al., 1998). For optimal extraction, the temperature ofthe water ranges from 80 to 100◦C. Temperatures over 100◦Care detrimental to polyphenols, which can cause denaturation.(Shi et al., 2005).

Extraction by water and ethanol solvent. The most common typeof extraction is done with alcohol-water solutions. Ethanoland water are the most widely employed solvents for hy-gienic and abundance reasons, respectively (Moure et al.,2001). Ethanol is a safe solvent that can be used for extrac-tion purposes, where even if it is found in the final extract, itis safe for human consumption (Shi et al., 2005). Alcoholicsolvents efficiently penetrate cell membranes, permitting theextraction of high amounts of endocellular material (Silvaet al., 1998).

Extraction by water and methanol solvent. This process is car-ried out at low temperatures to avoid oxidation. Methanolprovides as good results as ethanol. Hydrocinnamic deriva-tives, flavonols, and catechins are extracted using this solventmixture (Shi et al., 2005).

Extraction by ethyl acetate and water solvent. Ethyl acetate isa good solvent for polyphenols. It has a low polarity, thuscapable of extracting polyphenols that are dissolved in thelipid fraction of the food. The advantage lies in the fact thatit has a low boiling point, which makes it easy to remove andreuse (Shi et al., 2005).

The efficiencies of the various solvents mentioned weretested by several authors. Duh et al. (1992) found that amongthe organic solvents, the methanolic extract from peanut hullsproduced a higher yield, and the antioxidant component iden-tified from this extract was equal to the commercial antioxi-dant BHT and stronger than alpha-tocopherol. Nepote et al.(2002) extracted antioxidant components from defatted and non-defatted peanut skins using methanol, ethanol, acetone, and wa-ter. The high content of total phenolics was detected in themethanolic and ethanolic extracts from defatted peanut skins.Huang et al. (2003) also compared the yield and antioxidantactivity of peanut seed testa extracted using various solventsnamely: methanol, ethanol, acetone, hexane, and ethyl acetate.Among the solvent extracts, ethanol extracts produced the high-est yield and antioxidant activity, showing that polar solvents

were more efficient than less polar solvents in terms of extractionof antioxidative components. It was also evident that the antiox-idant activity of polar solvent extracts was markedly strongerthan that of less polar solvent extracts, which showed hardlyany antioxidant activity. In terms of the concentration of ethanolfor extraction, Nepote et al. (2005) found that both 50 and 70%(v/v) ethanol in water are the best solvents to extract a high yieldof total phenolic and antioxidant compounds in peanut skins.However, when considering the evaporation time and cost, thepreferred solvent mixture was 70% (v/v) ethanol in water.

Yu et al. (2005) on the other hand used ethyl acetate andwater in isolating phenolics also from peanut skins. Their studyrevealed that the water extract fraction from purified peanut skinextract shows higher total phenolics concentration than the ethylacetate portion. Based on the polarity of water and ethyl ac-etate, phenolic compounds in the water layer are more polar thanthose that would preferentially dissolve in ethyl acetate. Thus,water would favorably dissolve more polar plant polyphenolswith higher antioxidant activity. Higher polarity means morehydroxyl groups on the ring of polyphenols and based on theconclusion of Cao et al., (1997) the more hydroxyl substitu-tions, the stronger the antioxidant and prooxidant activities. Thisfinding is encouraging with the fact that functional ingredientsused in the formulation of health promoting foods and dietarysupplements need to be water soluble for optimal physiologicalbenefits (Yu et al., 2005).

The best conditions for the extraction of antioxidative com-pounds from peanut skins were established by Nepote et al.(2005) as follows: 70% ethanol as solvent, non-crushed peanutskins, ratio of solvent/solid of 20 ml/g, at 10 minutes shaking andthree extractions. At these conditions, the phenolic compoundsobtained were 118 mg/g. While the study of Yu et al. (2005)obtained high yield of phenolic compounds using peanut skinsfrom peanut kernels roasted at 175◦C for 5 min and extractedusing ethanol (80%) as recovery method.

Ultrasound-assisted Extraction

High-frequency ultrasound is a powerful technique that isbeing applied to material analysis research and food productdevelopment. The mechanical effects of ultrasound providegreater forced penetration of solvent into cellular materials; im-proves mass transfer to and from interfaces; and facilitates therelease of contents by disrupting the biological cell walls on thesurface and within the raw material (Mason, 1998). A cavitationphenomenon is produced during ultrasonication when acousticpower inputs are sufficiently high to allow the multiple pro-ductions of microbubbles that collapse and create shock wavesthat cause cells to disintegrate into very fine cell debris particles(Chukwumah et al., 2005). The ultrasound waves produce an in-crease in temperature and pressure, giving rise to advantageousincreases in transport phenomena and in the displacement of thepartitioning equilibrium (Waksmundzka-Hajnos et al., 2004).Advantages of ultrasound-assisted extraction include shorterextraction time, lower extraction temperature, and less bioac-tive compound loss (Liu et al., 2005).



A high-frequency ultrasonication method was used in extract-ing selected phytochemicals from peanuts. The results showedthat the amount of biochanin, genistein, and resveratrol in-creased with increasing extraction time and that the highestamount of biochanin and resveratrol was obtained at 150 minand 180 min for genistein (Chukwumah et al., 2005).

Measuring Bioactive Components with AntioxidativeProperties

Within a biological system, there are at least four generalsources of antioxidants: (1) enzymes (e.g. catalase, superox-ide dismutase); (2) large molecules (e.g. albumin); (3) smallmolecules (e.g. ascorbic acid, tocopherol, polyphenols) and (4)some hormones (e.g. estrogen) (Prior et al., 2005). In measur-ing the total antioxidant capacity of a biological sample, sev-eral methods are usually conducted because of the possibility ofinteraction among different antioxidants in vivo may make themeasurement of any individual antioxidant less representative ofthe overall antioxidant status (Prior and Cao, 1999). An increasein concentrations of antioxidants does not necessarily mean thatthere has been an increase in reactive species. At the same time,a decrease in antioxidant levels could be the result of either anincrease in reactive species that react with the antioxidants ora response to lower production of reactive species. Because ofthe complex interactions within cells, one test is normally notenough to understand precisely what is going on within the cell(Griffin and Bhagooli, 2004).

The chemistry behind the antioxidant capacity assays areclassified into two: assays based on hydrogen atom transfer(HAT) reactions and assays based on single electron transfer(SET).

HAT-based methods measure the classical ability of anantioxidant to quench free radicals by hydrogen donation(AH = any H donor)

X· + AH → XH + X· (1)

Antioxidant capacity measurements are based on competitionkinetics and the quantitation is derived from kinetic curves.HAT reactions are solvent and pH independent and are usuallyquite rapid. HAT-based methods generally are composed of asynthetic free radical generator, an oxidizable molecular probe,and an antioxidant. The presence of reducing agents, includingmetals, interferes with HAT assays and therefore may lead toerroneously high apparent reactivity (Prior et al., 2005).

The SET-based methods detect the ability of a potential an-tioxidant to transfer one electron to reduce any compound, in-cluding metals, carbonyls, and radicals.

X· + AH → X− + AH·+ (2)

AH·+ ↔ A· + H3O+ (3)

X− + H3O+ → XH + H2O (4)

M(III) + AH → AH+ + M(II) (5)

SET reactions are usually slow and can require long times toreach completion. SET methods are very sensitive to ascorbicacid and uric acid. While trace components and contaminantslike metals also interferes with the method, accounting for highvariability and poor reproducibility and consistency (Prior et al.,2005).

In foods, separating each antioxidant is costly and inefficient,thus, researchers develop methods to evaluate the total antioxi-dant capacity of a given good, where “total antioxidant capacity”means the integrated effects of all the antioxidants and if any,the synergistic effects of them (Wu et al., 2004a). A brief de-scription of some of the different antioxidant capacity methodsare discussed briefly and a summary is presented in Table 12.

The First International Congress on Antioxidant Methodswas convened in 2004 for the purpose of discussing the chemicalmethods for antioxidant content and activity in model systemsand foods, measurement of antioxidant capacity in food andbiological systems, and the in vitro and in vivo methods usedto estimate effectiveness in animals and man (Finley, 2005).From the evaluation of data presented in the Congress and in theliterature, it was proposed that three assays be considered forstandardization: the Folin-Ciocalteu method, the oxygen radicalabsorbance capacity assay, and the Trolox equivalent antioxidantcapacity assay (Prior et al., 2005).

Folin-Ciocalteu Procedure

This method was derived from the Folin-Denis colorimetrymethod introduced in 1912. This method is also based on thechemical oxidation of the reduced molecules by a mixture ofthe two strong inorganic oxidants, phosphotungstic and phos-phomolybdic acids. But unlike the “official method” for totalphenolics, the Folin-Denis colorimetry is subject to precipita-tions that interfere with colorimetry. The method, proposed byOtto Folin and Vintila Ciocalteu in 1927 is convenient, simple,requires only common equipment, and has produced a large bodyof comparable data. The assay is inclusive of monophenols andgives a predictable reaction with the types of phenols found innature. With the diverse nature of phenols, the degree of reactionis wide, such that the expression of the results as a single numbersuch as milligrams per liter gallic acid equivalence is necessar-ily arbitrary. Also, since the reaction is independent, quantita-tive, and predictable, an analysis of a mixture of phenols canbe recalculated in terms of any other standard (Singleton et al.,1999).

The Folin-Ciocalteu method has also some setbacks. Sincethe total phenolic content is determined based on nonspecificreduction-oxidation reactions, the analysis is affected by othernonphenolic reducing molecules present in the samples such asascorbate, citrate, and sulfite. Also, high sugars can form re-active reductones (endiols) in the final solution, and aromatic



Table 12 Comparison of methods for assessing antioxidant capacity (Prior et al, 2005; Prior and Cao, 1999).

Biological Coefficient of Lipophilic &Antioxidant Assaya Simplicity relevance Mechanismd Endpoint Quantitation variationf(%) Hydrophilic AOC

ORAC ++b Yes HAT Fixed time AUC n.d. + + +TRAP −−−c Yes HAT Lag phase IC50 lag time 4.6 −−FRAP + + + No SET Time, varies �OD fixed time n.d. − − −CUPRAC + + + SET Time �OD fixed time n.d. − − −TEAC + No SET Time �OD fixed time 3.6–6.1 + + +DPPH + No SET IC50 �OD fixed time n.d. −TOSC − Yes HAT IC50 AUC 6.0 − − −LDL oxidation − Yes HAT Lag phase Lag time n.d. − − −PHOTOCHEM + Yes ? Fixed time Lag time or AUCe 2.0 + + +Cyclic voltammetry + No HAT Anodic wave Peak potential n.d. − − −aORAC–Oxygen radical absorbance capacity; TRAP–Total radical trapping parameter assay; FRAP–Ferric reducing antioxidant power;CUPRAC–copper reduction assay; TEAC–Trolox equivalent antioxidant capacity assay; TOSC–Total oxidant scavenging capacity;PHOTOCHEM–Photochemiluminescenceb+, ++, + + + = desirable to highly desired characteristicc−, −−, − − − = less desirable to highly undesirable based upon this characteristicdHAT = hydrogen atom transfer; SET = single electron transfereThe lipophilic assay is quantified by AUC measured over a defined measuring time, and the hydrophilic assay is quantified based upon the lagphase.fInterassay coefficient of variation.

amines react, as phenols. These substances increase the ab-sorbance value by reacting with the Folin reagent and, if notcorrectly subtracted, can give an overestimated total phenolicvalue (Singleton, 1985; Stevanato et al., 2004).

ORAC Assay

The oxygen radical absorbance capacity (ORAC) methoduses phycoerythrin as an oxidizable protein substrate and AAPHas a peroxyl radical generator or Cu2+-H2O2 as a hydroxyl rad-ical generator (Prior and Cao, 1999). AAPH undergoes sponta-neous decomposition and produces peroxyl radicals, with a rateprimarily determined by temperature. The antioxidant samplesare not likely to affect this rate, particularly when the chemicalstructure of AAPH and the very high molar ratio of AAPH to anantioxidant sample are considered. Therefore, the ORAC assayhas high specificity; it measures the capacity of an antioxidantto directly quench free radicals. The area under-curve techniquecombines both inhibition percentage and the length of inhibitiontime of free radical action by an antioxidant into a single quan-tity, which makes it superior to similar methods that use either aninhibition percentage at a fixed time or a length of inhibition timeat a fixed inhibition percentage (Cao and Prior, 1998). Becauseperoxyl radicals are the most common radicals found in the hu-man body, ORAC measurements is more biologically relevant(Wu et al., 2004a; Wang et al., 2004). However, the ORAC assayrequires about 70 minutes to quantitate results (Prior and Cao,1999). Since the early version developed by Cao et al. (1993)was time-consuming and labor-intensive, an automated proce-dure was developed and modifications were also incorporatedsuch as the adoption of fluorescein as the new probe insteadof phycoerythrin. Phycoerythrin was found to lose 30–50% ofits intensity in the absence of free radicals due to photobleach-ing and it was also observed to cause nonspecific protein bind-

ing with the analyzed compounds, in particular with flavonoids(Huang et al., 2002). The developed ORACFL, according to theauthors, has the ability to obtain a measure of “total antioxidantcapacity” in the protein free plasma, using the same peroxyl rad-ical generator for both lipophilic and hydrophilic antioxidants(Wu et al., 2004a; Prior et al., 2003; Wu et al., 2004b).

ABTS Assay or TEAC Procedure

The assay is based on the ability of compounds to scav-enge the long-lived stable radical cation chromophore of 2,2′-azinobis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS·+).The radical is usually generated by oxidizing ABTS with met-myoglobin and hydrogen peroxide. The method, however, hasbeen criticized on the basis that the faster reacting antioxidantsmay also contribute to the reduction of the ferryl myoglobin rad-ical. An improved method was proposed and it utilizes potas-sium persulfate for the direct production of the ABTS radical(Re et al., 1999). This preformed ABTS radical is stable forat least two days when stored in the dark at room tempera-ture (Prior and Cao, 1999). The relative ability of hydrogen-donating antioxidants to scavenge ABTS·+ generated in theaqueous phase, can be measured spectrophotometrically in thenear-infrared region showing maxima at 660, 734 and 820 nm. Atthese wavelengths, the interference from other absorbing com-ponents and from sample turbidity is minimized. The results areexpressed by comparison with standard amounts of the syntheticantioxidant Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), to give rise to the TEAC (Trolox equivalentantioxidant capacity) in molar units. Trolox, a vitamin E ana-logue, is not a natural compound found in foods. A TEAC valuecan be assigned to all compounds by comparing their scaveng-ing capacity to that of Trolox. Thus, some authors refer thismethod as TEAC assay (Antolovich et al., 2002; Obon et al.,



2005; Kim and Lee, 2004; Arts et al., 2003). The ABTS·+ assayas demonstrated by several authors, can be used to measure theantioxidant activity of a broad diversity of substances such asL-ascorbic acid, glutathione, uric acid, albumin, bilirubin, cys-teine, BHT, α-tocopherol, phenolic acids, flavonoids, and cat-echins (Cano et al., 1998). Other modifications of the TEACassay exist: TEAC I (metmyoglobin) measures hydrophilic an-tioxidants; TEAC II (manganese dioxide) measures lipophilicantioxidants, while TEAC III (potassium persulfate) may be ap-plied for both. The three procedures vary on how the ABTSradical was generated (Aruoma, 2003).

Other Methods

The ABTS assay as well as other methods like ORAC usesTrolox equivalents to express antioxidant activity. But Trolox isnot a familiar compound to chemists. Furthermore, total antiox-idant capacity results expressed on a molar basis are difficultto understand. Vitamin C on the other hand, is commonly rec-ognized as a leading natural nutrient and antioxidant. Thus, thedescription of antioxidant potential using vitamin C equivalentantioxidant capacity (VCEAC) calculated on a weight basis wasproposed. The VCEAC assay also uses ABTS radicals, like theTEAC. The ABTS radical scavenging activity of selected chem-ical compounds at the level of 100 mg/L is expressed as mg/Lvitamin C equivalents (mg VCEAC/L) at 10 min (Kim and Lee,2004).

The DPPH method is representative of the methods employ-ing model radicals in the evaluation of radical scavengers. It isnot discriminative with respect to the radical species but givesa general idea about the radical quenching ability. The antirad-ical activity is defined as the amount of antioxidant necessaryto decrease the initial DPPH concentration by 50% (efficientconcentration = EC50 [(mol/l)AO/(mol/l)DPPH]. A direct rela-tion is observed where the larger the antiradical power is, themore efficient the antioxidative action is. The method is rapid,a sample analysis takes approximately 15 min in total and littlemanpower, and no expensive reagents or sophisticated instru-mentation is required (Aruoma, 2003; Koleva et al., 2002).

The ferric reducing antioxidant power (FRAP) assay involvesthe reduction of a ferroin analog, the Fe3+ complex of tripyridyl-triazine Fe(TPTZ)3+, to the intensely blue colored Fe2+ complexFe(TPTZ)2+ by antioxidants in acidic medium, pH of about 3.6.Results are obtained as absorbance increases at 593 nm and canbe expressed as micromolar Fe2+ equivalents or relative to anantioxidant standard (Antolovich et al., 2002; Aruoma et al.,2003).

The total radical trapping parameter (TRAP) assay wasthe most widely used method for measuring the total antioxi-dant capacity of plasma or serum. The TRAP assay uses per-oxyl radicals generated from an azo-compound, 2,2′-azobis(2-amidinopropane)dihydrochloride (ABAP), and peroxidizablematerials contained in plasma or other biological fluids. Af-ter adding ABAP to the plasma, the oxidation of the oxidizablematerial is monitored by measuring the oxygen consumed dur-

ing the reaction. During an induction period, this oxidation isinhibited by the antioxidants in the plasma. The length of theinduction period (lag phase) is compared to that of an internalstandard, Trolox, and then quantitatively related to the antioxi-dant capacity of the plasma (Prior and Cao, 1999).

Antioxidant Capacity of Peanuts

There are quite a few studies on the antioxidant capacity(AOC) of peanuts found in the literature. Hwang et al. (2001) ob-served that the antioxidative activities of roasted defatted peanutkernels at 180◦C for 60 min displayed the most remarkableAOCs on linoleic acid in emulsions where the induction periodwas determined to be about 200 hr in Tween 20 emulsion and350 hr in Tween 80 emulsion, compared to the control, raw, de-fatted peanuts of 12 hr. Wu et al. (2004a) examined the lipophilicand hydrophilic antioxidant capacities of common foods in theUnited States including nuts and nut products. Using the ORACassay, the hydrophilic ORAC values among different nuts wasquite large, ranging from 4.43 to 175.2 µmol of Trolox equiv-alents (TE) per gram for pine nuts and pecans, respectively.Peanuts had a lipophilic and hydrophilic ORAC of 2.73 and28.93 µmol TE per gram, respectively, for a total antioxidantcapacity of 899 µmol TEs per serving (serving size = 28.4 g).Peanut butter had a total of 34.32 µmol TE per gram.

The AOC of normal and high oleic acid peanuts were foundto be relatively high in raw and roasted peanuts and increasedby 22% on average following roasting (Talcott et al., 2005b).However, no meaningful differences in AOC were observed be-tween high and normal oleic acid peanuts, but differences werepresent among cultivars (Talcott et al., 2005b). Total phenolicsin 10 different nut types were analyzed by Kornsteiner et al.(2006) and the mean content of total phenolics ranged from 32mg GAE/100 g (pine nuts) and 1,625 mg (walnuts). Raw peanutswith skin had a mean of 420 mg GAE/100 fresh weight.

The use of defatted peanut skin as raw material was exploredby Nepote et al. (2004). They found that the methanolic andethanolic defatted peanut skin extract contains about 158.6 mg/gand 144.1 mg/g total phenolics, respectively. The radical scav-enging activities were 32.59% in methanolic extract and 31.5%in ethanolic extract at a concentration of 1 µg/ml. Yen et al.(2005) found that the AOC of the ethanolics and the isolated an-tioxidative component from the extract of peanut seed testa, ethylprotocatechuate, revealed 92.6% and 84.6% scavenging effect,respectively, on α,α-diphenyl-β-picrylhydrazyl (DPPH) radical.The hydroxyl radical scavenging effect of ethanolic extract andethyl protocatechuate were 70.6% and 67.7%, respectively.

The total AOC of the water and ethanol extracts of peanutskins were compared with the water and ethanol extract of greentea, the latter known to have high AOC. Under identical extrac-tion and analytical conditions, Yu et al. (2005) reported thatextracts from peanuts skins showed higher AOC than greentea. The antioxidant capacities of water and ethanol extractsof raw peanut skins were 3.39 and 4.10 (mM Trolox/mM phe-nolics) respectively. Roasted peanut skins had 3.30 and 3.72



(mM Trolox/mM phenolics) for water and ethanol extracts, re-spectively. While green tea had 1.91 and 2.46 (mM Trolox/mMphenolics) of the water and ethanol extract, respectively. Resultsalso show that one gram of peanut skin contains 90 to 125 mgtotal phenolics, the amount of which is comparable with grapeskin and grape seeds. A follow up study by Yu et al. (2006)revealed that the water and ethanol extracts from peanut skinshowed higher free radical scavenging activity as compared toTrolox and Vitamin C.

The antioxidant and membrane effects of procyanidin dimers(dim) and trimers (tri) isolated from peanut skins were exam-ined and compared with those of the procyanidins found in co-coa. Procyanidins of the B- and C- bonded types were isolatedfrom cocoa whereas the A-type procyanidins were isolated frompeanut skins. All types were evaluated in protecting phosphatidylcholine liposomes from Triton X-100-mediated disruption. Themagnitude of the protection was strongest for the A-types thanB and C-types (dim A1 > dim A2 > dim B and trim C > tri A(Verstraeten et al., 2005). A summary of AOC of peanuts andpeanut by-products are listed in Table 13.

The antioxidant activities of other nutshells like pistachio,walnut, and almond have also been determined. The vitaminC equivalent antioxidant capacity (VCEAC) of the ten com-

monly consumed nuts in the US showed walnuts (4581 ± 11 µMVCE/g), followed by pecans and peanuts as the top three com-modities with high VCEAC values (Yang et al., 2005). Whereasthe study of Wu et al. (2004a) revealed pecans, walnuts, andhazelnuts as the top three nuts with high total antioxidant capac-ity using the ORAC assay.

Pistachio hull extract was effective in retarding oil deteriora-tion at 60◦C, with increasing activity at concentrations between0.02–0.06%. The study also shows that pistachio hull extractwas comparable to BHA and BHT (Goli et al., 2005). The cor-responding scavenging activity of the superoxide radical of thealmond seed, skin and shell cover was 75.5, 88.9, and 97.4% at100 ppm, respectively, while the reduction of hydrogen peroxideconcentration at 100 ppm was 59.8, 62.6, and 65.6 for seed, skin,and shell cover, respectively (Siriwardhana and Shahidi, 2002).Total antioxidant capacity of the ethanolic extracts of almondskin was also evaluated to be 13 times greater than that of thewhole seed extract at the same concentration. Free radical scav-enging activity of the brown skin was recorded to be 100% forDPPH and hydroxyl radical at 200 and 100 ppm, respectively(Siriwardhana and Shahidi, 2002). Two out of nine compoundsisolated from almond skin showed very strong radical scaveng-ing activity against DPPH (Sang et al., 2002).

Table 13 Antioxidant activities of peanuts, peanut butter, and peanut by-products.

Sample (solvent) Antioxidant activity assay Activity (conc. antioxidant)1 Reference

Peanut kernels (hexane/dichloromethane; acetone/water/acetic acid)

Oxygen radical absorbancecapacity

L-ORACFL, 2.73 µmol Trolox/g Wu et al., 2004

H-ORACFL, 28.93 µmol Trolox/gPeanut kernel, Ga. Green

(methanol)Oxygen radical absorbance

capacityTEAC, 26.9 µM Trolox equi/g

(raw); 32.3 µM Trolox equi/g(roasted)

Talcott et al., 2005b

Peanut kernels, roasted,defatted (water)

Linoleic acid oxidation OS (Tween 20, 20 mg/ml), 200 h Hwang et al., 2001OS (Tween 80, 20 mg/ml), 350 h

Peanut hulls (methanol) DPPH radical scavenging I (extract 1.5 mg/ml), 89.3% Yen and Duh, 1994I (BHA 240 µM), 92.6%I (catechin 8 µM), 89.3%

Peanut hulls (methanol) Linoleic acid oxidation AA (9.6 mg), 96.1–96.8% Yen and Duh, 1995Peanut hulls (methanol) Soybean and peanut oil

oxidationOS (0.48%), 194 h Duh and Yen, 1997OS (1.20%), 292 hOS (0.01% BHA), 143 hOS (control), 107 h

Peanut hulls (methanol) Linoleic acid oxidation IC50 (10 µl), 111 ppm Kuo et al., 1999Peanut hulls, irradiated (water) DPPH and reducing power I (extract 300 mg/10ml), 48.83% Lee et al., 2006

A (extract 300 mg/10ml), 0.910Peanut skin (ethanol) DPPH and hydroxyl radical

scavengingI (extract 100 mg/l), 92.6% Yen et al., 2005I (extract 200 mg/l), 70.6%

Peanut skin (methanol andethanol)

DPPH radical scavenging I (methanol, 1 µg/l), 32.59% Nepote et al., 2002I (ethanol, 1µg/l), 31.5%

Peanut leaves (methanol) Oxidative stability index OS (extract 0.5 g equiv), ∼30 h Green and Sanders, 2004OS (BHT 10 mg), ∼20 h

Peanut butter (hexane/dichloromethane; acetone/water/acetic acid)

Oxygen radical absorbancecapacity

L-ORACFL, 3.05 µmol Trolox/g Wu et al., 2004H-ORACFL, 31.27 µmol Trolox/g

1AA, Antioxidant activity (thiocyanate method), calculated as percentage of inhibition of peroxidation of linoleic acid; BHA, butylatedhydroxyanisole; BHT, butylated hydroxytoluene; DDPH, α,α-diphenyl-β-picrylhydrazyl; IC50, Inhibitory concentration for 50% inhibition inthe reduction of oxidation; L-ORACFL, Lipophilic ORAC assay with fluorescein; H-ORACFL, Hydrophilic ORAC assay with fluorescein; OS,Oxidative stability; I, percent inhibition; A, absorbance, for measuring reducing power; TEAC, Trolox equivalent antioxidant activity.



EFFECTIVE PROCESSING METHODS TO INCREASETHE CONCENTRATION OF BIOACTIVE COMPOUNDSIN PEANUTS

Many antioxidative phenolic compounds in plants are presentas a covalently bound form with insoluble polymer. To obtainnatural antioxidants from plants, it is necessary to find an effec-tive processing method to liberate them. Several methods suchas heat treatment and far-infrared radiation have been studied toliberate and activate low molecular weight natural antioxidants(Jeong et al., 2004a; 2004b). Secondary sources of antioxidantslike Maillard reaction products will also be discussed.

Heat Treatment

Most of the phenolic compounds found in the outer layers ofplants such as peel, shell, and hull are high in concentration toprotect inner materials such as the seed. A number of phenolicacids, however, are covalently bound with insoluble polymersand other cell wall components such as arabinoxylans and pro-teins (Jeong et al., 2004a; Lee et al., 2006). Simple heat treatmentcan liberate the low molecular antioxidant compounds from therepeating subunits of high molecular weight polymers (Jeonget al., 2004a). However, an effective processing step for liberat-ing antioxidant compounds from different plant species may notbe the same. For example, simple heat treatment could not cleavecovalently bound phenolic compounds from rice hulls (Lee etal., 2003) but in grape seeds, several low-molecular weight phe-nolic compounds were newly formed in heat treated grape seedsat 150◦C for 40 min (Kim et al., 2006). Talcott et al. (2005b) alsoreported an increase in the level of p-coumaric acid was obtainedwhen normal and high oleic acid peanuts were roasted at 175◦Cfor 10 min. Free and bound forms of p-coumaric acid wereobtained previously, and thus, the increase in concentration maybe due to the release of free p-coumaric acids by heat-catalyzedhydrolytic reactions from its native esterified or bound forms.

Simple heat treatment of peanut hulls at 150◦C for 60 minalso increased the total phenol contents, the radical scavengingactivity, and the reducing power of the water extract from peanuthulls. The results showed that the phenol content increased from72.9 to 90.3 µM, the scavenging activity increased from 1.90%to 23.69% and the reducing power increased from 0.471 to 0.718,compared to the untreated controls (Lee et al., 2006).

Polyphenols exist naturally in foods, serving as a primarysource of antioxidants. During food processing and storage,degradation of natural antioxidants may occur. On the otherhand, chemical reactions among food components may lead tothe formation of secondary antioxidants. Important candidatesfor secondary food antioxidants are Maillard reaction products(Dittrich et al., 2003). During processing, cooking, or storage offoods, many complex physical and chemical changes in foodsoccur. The major compositional changes occurring are decreasesin protein, amino acids, reducing sugars, water, and the forma-tion of melanoidins. Many of these changes are due to Maillard

reaction. The first stage of Maillard reaction is the formation ofAmadori rearrangement products that may be further degradedupon storage or easily formed at high temperature conditionssuch as baking and roasting. Exposure to high temperature, how-ever, may have some limitations on the production of Maillardreaction products (MRP) since based on a study using modelsolutions heated at 120◦C for 10 to 30 min resulted in a decreasein radical scavenging activity of the MRP as time of exposure in-creases, possibly due to the degradation of the antioxidant MRP(Yilmaz and Toledo, 2005). Maillard reaction products formedin foods are reported to possess various types of antioxidantactivity such as metal chelators and even pro-oxidant properties,and since then antioxidant activities of Maillard products havebeen extensively studied (Rajalakshmi and Narasimhan, 1996;Dittrich et al., 2003; Del Castillo et al., 2002; Mastrocola andMunari, 2000). The predominant antioxidants appeared to be thelow molecular weight fraction of MRPs containing compoundssuch as reductones and maltol (Alfawaz et al., 1994). Dittrichet al. (2003) confirmed in their study that Maillard products,particularly those with amino reductone structure, have a strongpotential to inhibit LDL oxidation.

In addition to reducing sugars, other carbonyl compounds in-cluding lipid peroxidation products are also able to react withamino groups, producing brown macromolecular pigments withproperties similar to those of melanoidins (Hidalgo et al., 1999).The antioxidative effect of the products formed by the reactionof oxidized lipids with amino acids and protein in a preheatedmodel system was studied by Mastrocola and Munari (2000).They found out that the MRPs had the ability to retard perox-ide formation and that the antioxidant activity developed withincreased browning of the samples.

The effect of roasting conditions on the AOC of various rawmaterials have been investigated and the results indicate a signif-icant increase in total phenolic content, radical scavenging ac-tivity, reducing powers, and AOC as a function of roasting timeand temperature (Jeong et al., 2004a; 2004b; Yanagimoto et al.,2002; Yen and Chuang, 2000; Lee et al., 2006). Long roastingtimes have been observed the result in increased oxidative stabil-ity in peanuts. In general, the longer the roasting time, the moreextensive are the browning reactions, with resultant decreasesin free amino acids and soluble carbohydrates (Chiou, 1992).

Irradiation

Far-infrared (FIR) rays are defined as electromagnetic waveshaving a wavelength of longer than 4 µm but shorter than mi-crowaves (λ > 0.1 cm). FIR rays are biologically active andtransfer heat to the center of materials evenly, without degrad-ing the constituent molecules of the surface (Lee et al., 2003).Reports show that FIR radiation liberates and activates low-molecular-weighted natural antioxidants in plants. FIR may havethe capability to cleave covalent bonds and liberate antioxidantssuch as flavonoids, carotene, tannin, ascorbate, flavoprotein, orpolyphenols from repeating polymers (Lee et al., 2006).



The antioxidant activities of peanut hull extracts were evalu-ated after FIR radiation for 5 to 60 min by Lee et al. (2006). Theyfound that the total phenolic content, radical scavenging activ-ity, and reducing power of the peanut hull extract increased asthe time of exposure to FIR increased. Total phenolic content ofwater extracts of peanut hulls increased from 72.9 to 141.6 µM,radical scavenging activity increased from 2.34% to 48.83%,and reducing power increased from 0.473 to 0.910, respectively,compared to the untreated controls (Lee et al., 2006).

Harrison and Were (2006) used gamma irradiation to increasethe phenolic content and antioxidant capacity of almond skinethanolic extracts. Almond skin extracts irradiated at 4 kGy(trial 1) or 12.7 kGy (trial 2) exhibited higher phenolic contentthan the control (0 kGy) as well as greater scavenging abilitycompared to non-irradiated extract as determined by TEAC. Inaddition, phenolic extracts from 16.3 8 kGy irradiated skins hadsignificantly lower conjugated dienes values than the controland Trolox samples after 24 hours of storage. Peroxide val-ues were likewise lower for irradiated extracts compared to thecontrol.

FUNCTIONALITY EFFECTS OF PHYTOCHEMICALSFROM PEANUTS IN FOODS

Antioxidants

The antioxidative effect of extracts obtained from peanut skinand hulls on various products were studied (Nepote et al., 2004;Duh, and Yen, 1997; Rehman, 2003; O’Keefe et al., 2003).Methanolic extracts of peanut hulls and BHA in soybean andpeanut oils were compared after accelerated oxidation at 60◦C.Samples containing the peanut hull extract showed lower perox-ide values and acid values compared with the untreated controls.Moreover, the methanolic extract of peanut hulls was signifi-cantly better than BHA-treated samples in reducing oxidationof both oils (Duh and Yen, 1997). Rehman (2003) conducted astudy on the antioxidant activity of methanolic extract of peanuthulls for fried potato chips by adding the extracts to sunfloweroil at 800, 1200, and 1600 ppm, to be used for frying the potatochips. The extract exhibited very strong antioxidant activities,almost equal to synthetic antioxidants like BHA and BHT. Theyfound acceptable ratings, lower values of free fatty acids, andperoxide values in potato chips treated with 1200 and 1600 ppmof extract stored at 45◦C for six months, compared to the con-trol samples. Color, flavor, taste, and overall acceptability scoreswere significantly higher for treated potato chips than the con-trol, fried in oil without antioxidants, while no significant dif-ference was obtained between samples with peanut hull extractand samples treated with synthetic antioxidants. Methanol andethanol extracts of peanut hulls were also evaluated in peanutpastes and cooked minced chicken by O’Keefe et al. (2003)Peanut pastes were spiked with peanut hull extracts and storedat 40◦C for 7–10 days, while cooked minced chicken was storedat 8◦C for 4 days. Results show significant AOC in the foods

investigated and that significant differences in activity of peanuthull extracts exist between methanol and ethanol but the authorsdid not indicate what the differences are.

The antioxidant activity of peanut skin extract in muscle foodswas investigated by O’Keefe and Wang (2006). The most signif-icant reduction in oxidation (TBARS) was obtained in groundbeef at 14 days of storage, and in ground beef samples with addi-tional salt. No changes were observed in terms of color, althoughthe extract added a slight red color to the sample. Sensory aromaand cooking loss were not affected by the addition of extract, aswell as the microbial growth in fresh ground beef.

Methanolic extracts from defatted and non-defatted peanutskins were evaluated in sunflower oil stored at 60◦C to induceoxidation (Nepote et al., 2000). Samples containing the two ex-tracts individually had lower peroxide value in comparison withuntreated controls. However, the antioxidant activity of bothpeanut skin extracts was lower than of the commercial BHT.Another study by Nepote et al. (2004b) involved honey roastedpeanuts with 0.02% (w/w) peanut skin extract. Peroxide andTBARS increased across the storage time for all samples for126 days, as did oxidized and cardboard flavors. However, theroasted peanutty flavor decreased. The addition of natural an-tioxidants from peanut skins did not affect the acceptance of theproduct by consumers. Peanut skin extract protected the peanutsagainst lipid oxidation, however, to a lesser extent compared withBHT.

Antimicrobial Agents

The effect of peanut tannins on the growth of A. parasiti-cus was investigated by Sanders and Mixon (1979) and Azaizehet al. (1990) Seed coat tannin, methanol-extracted, water-solublematerial from the peanut seed coats was tested in vitro, andthe results showed that as the concentration of tannins in-creased to 7.5%, inhibition of fungal growth increased linearlyto 88% (Sanders and Mixon, 1979). Similarly, when some ofthe methanol-extracted and water soluble tannin extracts wereincorporated in yeast extract sucrose liquid medium, the growthof A. parasiticus was significantly inhibited and the levels ofaflatoxin reduced (Azaizeh et al., 1990).

The antimicrobial effect of phenolic compounds is probablyrelated to the inhibition of bacterial enzymes, alterations in cellwall permeability, an increase in the hydrogen ion activity of themicrobial environment, a reduction in the surface and/or inter-facial tension, and chelation of essential minerals, particularlyiron (O’Connell and Fox, 2001).

CONCLUSION

Peanuts, peanut products, and its byproducts—roots, leaves,hulls, skins, and kernels are a highly potential source of func-tional and beneficial components that exhibit wide biologicaland practical applications that are of great interest to the foodindustry. There is substantial evidence that peanuts are packed



with bioactive compounds, therefore, it would be worthwhileto further embark on experimentation and investigation on thefunctionality of this valuable agricultural crop.

REFERENCES

Aherne, S. A., and O’Brien, N. M. (2002). Dietary flavonols: Chemistry, foodcontent and metabolism. Nutrition. 18:75–81.

Albert, C. M., Gaziano, J. M., Willet, W. C., and Manson, J. E. (2002). Nutconsumption and the risk of sudden and total cardiac death in the physicianshealth studys. Arch. Intern. Med. 162:1382–1387.

Alfawaz, M., Smith, J. S., and Jeon, I. J. (1994). Maillard reaction products asantioxidants in pre-cooked ground beef. Food Chemistry. 51:311–318.

Antolovich, M., Prenzler, P. D., Patsalides, E., McDonald, S., and Robards, K.(2002). Methods for testing antioxidant activity. Analyst. 127:183–198.

Arts, I. C. W., and Hollman, P. C. H. (2005). Polyphenols and disease risk inepidemiological studies. Am. J. Clin. Nutr. 81(suppl):317S–325S.

Arts, M. J. T. J., Dallinga, S., Voss, H. P., Haenen, G. R. M. M., and Bast, A.(2003). A critical appraisal of the use of the antioxidant capacity (TEAC) assayin defining optimal antioxidant structures. Food Chemistry. 80:409–414.

Aruoma, O. I. (2003). Methodological considerations for characterizing po-tential antioxidant actions of bioactive components in plant foods. MutationResearch. 523-524:9–20.

Awad, A. B., Chan, K. C., Downie, A. C., and Fink, C. S. (2000). Peanuts asa source of β-sitosterol, a sterol with anticancer properties. Nutrition andCancer. 36:238–241.

Awad, A. B., Hartati, M. S., and Fink, C. S. (1998). Phytosterol feeding inducesalteration in testosterone metabolism in rat tissues. J. Nutr. Biochem. 9:712–717.

Azaizeh, H. A., Pettit, R. E., Sarr, B. A., and Phillips, T. D. (1990).Effect of peanut tannin extracts on growth of Aspergillus parasiti-cus and aflatoxin production – Abstract, Mycopathologia, 110:125–132.http://www.springerlink.com [Accessed on 5/4/2006].

Birt, D. F., Hendrich, S., and Wang, W. (2001). Dietary agents in cancer preven-tion: flavonoids and isoflavonoids. Pharmacology and Therapeutics. 90:157–177.

Cano, A., Hernandez-Ruiz, J., Garcia-Canovas, F., Acosta, M., and Arnao, M.B. (1998). An end-point method for estimation of the total antioxidant activityin plant material. Phytochemical Analysis. 9:196–202.

Cao, G., and Prior, R. L. (1998). Comparison of different analytical methods forassessing total antioxidant capacity of human serum. Clin. Chem. 44:1309–1315.

Cao, G., Alessio, H. M., and Cutler, R. G. (1993). Oxygen-radical absorbancecapacity assay for antioxidants. Free Radical Biology & Medicine. 14:303–311.

Cao, G., Sofic, E., and Prior, R. L. (1997). Antioxidant and prooxidant behaviorof flavonoids: structure-activity relationships. Free Rad. Biol. Med. 22:749–760.

Cassidy, A., Hanley, B., and Lamuela-Raventos, R. M. (2000). Isoflavones, lig-nans and stilbenes – origins, metabolism, and potential importance to humanhealth. J. Sci. Food Agric. 80:1044–1062.

Chang, J. C., Lai, Y. H., Djoko, B., Wu, P. L., Liu, C. D., Liu, Y. W., andChiou, R. Y. Y. (2006). Biosynthesis enhancement and antioxidant andanti-inflammatory activities of peanut (Arachis hypogaea L.) arachidin-1,arachidin-3, and isopentadienylresveratrol. J. Agric. Food Chem. 54:10281–10287.

Chen, R. S., We, P. L., and Chiou, R. Y. Y. (2002). Peanut roots as a source ofresveratrol. J. Agric. Food Chem. 50:1665–1667.

Cheynier, V. (2005). Polyphenols in foods are more complex than often thought.Am. J. Clin. Nutr. 81(suppl):223S–229S.

Chiou, R. Y. Y. (1992). Antioxidative activity in oils prepared from peanutkernels subjected to various treatments and roasting. J. Agric. Food Chem.40:1958–1962.

Chukwumah, Y. C., Walker, L. T., Verghese, M., Bokanga, M., Ogutu, S., andAlphonse, K. (2007) Comparison of extraction methods for the quantificationof selected phytochemicals in peanuts (Arachis hypogaea). J. Agric. FoodChem. 55:285–290.

Chukwumah, Y., Walker, L. T., Verghese, M., Ogutu, S., and Bokanga, M. (2005).Extraction of selected phytochemicals from peanuts (Arachis hypogaea L.)using high-frequency ultrasonication method. Abst# 99B-24, 2005 IFT An-nual Meeting, July 15–20, New Orleans, Louisiana.

Chun, O. K., Kim, D. O., Smith, N., Schroeder, D., Han, J. T., and Lee, C. Y.(2005) Daily consumption of phenolics and total antioxidant capacity fromfruit and vegetables in the American diets. J. Sci. Food Agric. 85:1715–1724.

Chung, I. M., Park, M. R., Chun, J. C., and Yun, S. J. (2003). Resveratrolaccumulation and resveratrol synthase gene expression in response to abioticstresses and hormones in peanut plants. Plant Science. 164:103–109.

Clifford, M. N. (2000). Chlorogenic acids and other cinnamates – nature, oc-currence, dietary burden, absorption and metabolism. J. Sci. Food Agric.80:1033–1043.

Cornwell, T., Cohick, W., and Raskin, I. (2004). Dietary phytoestrogens andhealth. Phytochemistry. 65:995–1016.

Dabrowski, K. J., and Sosulski, F. W. (1984). Composition of free and hy-drolysable phenolic acids in defatted flours of ten oilseeds. J. Agric. FoodChem. 32:128–130.

Daigle, D. J., Conkerton, E. J., Sander, T. H., and Mixon, A. C. (1988). Peanuthull flavonoids: Their relationship with peanut maturity. J. Agric. Food Chem.36:1179–1181.

Del Castillo, M. D., Ames, J. M., and Gordon, M. H. (2002). Effect of roasting onthe antioxidant activity of coffee brews. J. Agric. Food Chem. 50:3698–3703.

Dittrich, R., El-Massry, F., Kunz, K., Rinaldi, F., Peich, C. C., Beckmann, M. W.,and Pischetsrieder, M. (2003). Maillard reaction products inhibit oxidation ofhuman low-density lipoproteins in vitro. J. Agric. Food Chem. 51:3900–3904.

Drewnowski, A., and Gomez-Carneros, C. (2000). Bitter taste, phytonutrients,and the consumer: a review. Am. J. Clin. Nutr. 72:1424–1435.

Duh, P. D., and Yen, G. C. (1995). Changes in antioxidant activity and compo-nents of methanolic extracts of peanut hulls irradiated with ultraviolet light.Food Chemistry. 54:127–131.

Duh, P. D., and Yen, G. C. (1997). Antioxidant efficacy of methanolic extractsof peanut hulls in soybean and peanut oils. JAOCS Abstracts, Paper no. J7893in JAOCS. 74:745–748.

Duh, P. D., Yeh, D. B., and Yen, G. C. (1992). Extraction and identification ofan antioxidative component from peanut hulls. JAOCS. 69(8):814–818.

EU Scientific Committee on Food. (2000). Opinion of the Scientific Committeeon Food on a request for the safety assessment of the use of phytosterol estersin yellow fat spreads, http://europa.eu.int/comm/food/fs/sc/scf/out56 en.pdf[Accessed on 06/14/2005].

EU Scientific Committee on Food. (2002). General view on the long-term effects of the intake of elevated levels of phytosterols from mul-tiple dietary sources, with particular attention to the effects on Beta-carotene. http://europa.eu.int/comm/food/fs/sc/scf/out143 en.pdf [Accessedon 06/14/2005].

European Food Safety Authority (2003). Opinion of the scientific panel on di-etetic products, nutrition and allergies on a request from the Commissionrelated to a novel food application from Forbes Medi-Tech for approvalof plant sterol-containing milk-based beverages. The EFSA Journal, 15:2–12.

Fang, Y. Z., Yang, S., and Wu, G. (2002). Free radicals, antioxidants, and nutri-tion. Nutrition. 18:872–879.

Finley, J. W. (2005). Introduction: White papers from the “First Interna-tional Congress on Antioxidant Methods”. J. Agric. Food Chem. 53:4288–4289.

Fraser, G. E., Sabate, J., Beeson, W. L., and Strahan, T. M. (1992). A possibleprotective effect of nut consumption on risk of coronary heart disease. TheAdventist Health Study. Arch Intern Med. 152:1416–1424.

Freedman, J. E., Parker III, C., Li, L, Perlman, J. A., Frei, B., Ivanov, V., Deak,L. R., Iafrati, M. D., and Folts, J. D. (2001). Select flavonoids and whole juicefrom purple grapes inhibit platelet function and enhance nitric oxide release.Circulation. 103:2792–2798.



Garvin, S., Ollinger, K., and Dabrosin, C. (2006). Resveratrol induces apoptosisand inhibits angiogenesis in human breast cancer xenografts in vivo. CancerLetters. 231:113–122.

Goli, A. H., Barzegar, M., and Sahari, M. A. (2005) Antioxidant activity andtotal phenolic compounds of pistachio (Pistachia vera) hull extracts, FoodChemistry. 92:521–525.

Green, R., and Sanders, T. (2004). Antioxidant activity of peanut plant parts,Abst# 67B-31, IFT Annual Meeting, July 1–6, Las Vegas, NV.

Griel, A. E., Eissenstat, B., Juturu, V., Hsieh, G., and Kris-Etherton, P. M. (2004).Improved diet quality with peanut consumption. J. of the Am. Coll. Nutr.23:660–668.

Griffin, S. P., and Bhagooli, R. (2004). Measuring antioxidant potential in coralsusing the FRAP assay. J. Experimental Marine Biology & Ecology. 302:201–211.

Grosso, N. R., and Guzman, C. A. (1995). Chemical composition of aboriginalpeanut (Arachis hypogaea L.) seeds from Peru. J. Agric. Food Chem. 43:102–105.

Grosso, N. R., Nepote, V., and Guzman, C. A. (2000). Chemical composition ofsome wild peanut species (Arachis L.) seeds. J. Agric. Food Chem. 48:806–809.

Grosso, N. R., Zygadlo, J. A., Lamarque, A. L., Maestri, D. M., and Guzman, C.A. (1997). Proximate, fatty acid and sterol compositions of aboriginal peanut(Arachis hypogaea L.) seeds from Bolivia. J. Sci. Food Agric. 73:349–356.

Gu, L., Kelm, M. A., Hammerstone, J. F., Beecher, G., Holden, J., Haytowitz, D.,and Prior, R. L. (2003). Screening of foods containing proanthocyanidins andtheir structural characterization using LC-MS/MS and thiolytic degradation.J. Agric. Food Chem. 51:7513–7521.

Gu, L., Kelm, M. A., Hammerstone, J. F., Beecher, G., Holden, J., Haytowitz, D.,Gebhardt, S., and Prior, R. L. (2004). Concentrations of proanthocyanidins incommon foods and estimations of normal consumption. J. Nutr. 134:613–617.

Guerrero, J. A., Lozano, M. L., Castillo, J., Benavente-Garcia, O., Vicente, V.,and Rivera, J. (2005). Flavonoids inhibit platelet function through binding tothe thromboxane A2receptor, JTH Abstract, J. Thrombosis and Haemostasis.3:369.

Hagiwara, A., Hirose, M., Takahashi, S., Ogawa, K., Shirai, T., and Ito, N.(1991). Forestomach and kidney carcinogenicity of caffeic acid in F344 ratsand C57BL/6N x C3H/HeN F1 mice. Cancer Research. 51:5655–5660.

Harrison, K, and Were, L. M. (2006). Effect of gamma irradiation on totalphenolic content yield and antioxidant capacity of almond skin extracts, FoodChemistry. doi:10.1016/j.foodchem.2006.06.034.

Havsteen, B. H. (2002). The biochemistry and medical significance of theflavonoids. Pharmacology and Therpeutics. 96:67–202.

Heim, K. E., Tagliaferro, A. R., and Bobilya, D. J. (2002). Flavonoid antioxi-dants: chemistry, metabolism and structure-activity relationships. J. of Nutr.Biochem. 3:572–584.

Hidalgo, F. J., Alaiz, M., and Zamora, R. (1999). Effect of pH and temperatureon comparative non-enzymatic browning of proteins produced by oxidizedlipids and carbohydrates. J. Agric. Food Chem. 47, 742–747.

Higgs, J. (2003). The beneficial role of peanuts in the diet – Part 2. Nutritionand Food Science. 33:56–64.

Hollman, P. C. H., and Arts, I. C. W. (2000). Flavonols, flavones and flavanols–nature, occurrence and dietary burden. J. Sci. Food Agric. 80:1081–1093.

Hu, F. B., Stampfer, M. J., Manson, J. E., Rimm, E. B., Colditz, G. A., Rosner,B. A., Speizer, F. E., Hennekens, C. H., Willett, and W. C. (1998). Frequentnut consumption and risk of coronary heart disease in women: prospectivecohort study. BMJ. 317:1341–1345.

Huang, D., Ou, B., Hampsch-Woodill, M., Flanagan, J. A., and Prior, R.L. (2002). High-throughput assay of oxygen radical absorbance capacity(ORAC) using a multichannel liquid handling system coupled with a mi-croplate fluorescence reader in 96-well format. J. Agric. Food Chem. 50:4437–4444.

Huang, S. C., Yen, G. C., Chang, L. W., Yen, W. J., and Duh, P. D. (2003).Identification of an antioxidant, ethyl protocatechuate, in peanut seed testa.J. Agric. Food Chem. 51:2380–2383.

Hwang, J. Y., Shue, Y. S., and Chang, H. M. (2001). Antioxidative activity ofroasted and defatted peanut kernels. Food Res. Inter. 34:639–647.

Ibern-Gomez, M., Roig-Perez, S., Lamuela-Raventos, R. M., and Dela Torre-Boronat, M. C. (2000). Resveratrol and piceid levels in natural and blendedpeanut butters. J. Agric. Food Chem. (2000) 48:6352–6354.

IFIC. (2004). Background on functional foods, International Food InformationCouncil, (IFIC) Foundation; http://ific.org/nutrition/functional/index.cfm.[Accessed on 06/14/2005].

IFST. (2005). Phytosterol esters (Plant sterol and stanol esters).http://www.ifst.org/hottop29.htm [Accessed on 06/09/05].

Jeong, S. M., Kim, S. Y., Kim, D. R., Jo, S. C., Nam, K. C., Ahn, D. U., and Lee,S. C. (2004a). Effect of heat treatment on the antioxidant activity of extractsfrom citrus peels. J. Agric. Food Chem. 52:3389–3393.

Jeong, S. M., Kim, S. Y., Kim, D. R., Nam, K. C., Ahn, D.U., and Lee, S.C. (2004b). Effect of seed roasting conditions on the antioxidant activity ofdefatted sesame meal extracts. J. Food Sci. 69(5):377–381.

Karakaya, S. (2004). Bioavailability of phenolic compounds. Crit. Rev. FoodSci. Nutr. 44:453–464.

Karchesy, J. J., and Hemingway, R. W. (1986). Condensed tannins:(4β →8;2β → O →7)-linked procyanidins in Arachis hypogoea L. J. Agric.Food Chem. 34:966–970.

Kim, D. O., and Lee, C. Y. (2004). Comprehensive study on Vitamin C equivalentantioxidant capacity (VCEAC) of various polyphenolics in scavenging a freeradical and its structural relationship. Crit. Rev. Food Sci. Nutr. 44:253–273.

Kim, S. Y., Jeong, S. M., Park, W. P., Nam, K. C., Ahn, D.U., and Lee, S. C.(2006). Effect of heating conditions of grape seeds on the antioxidant activityof grape seed extracts. Food Chemistry. 97:472–479.

Knekt, P., Kumpulainen, J., Jarvinen, R., Rissanen, H., Heliovaara, M., Reuna-nen, A, Hakulinen, T., and Aromaa, A. (2002). Flavonoid intake and risk ofchronic diseases. Am. J. Clin. Nutr. 76:560–568.

Koehler, P. E., and Song, L. H. (2002). Changes in phytosterols of peanuts duringmaturation, Abst# 61D-23, 2002 Annual Meeting and Food Expos. Anaheim,California.

Koleva, I. I., van Beek, T. A., Linssen, J. P. H., de Groot, A., and Evstatieva, L.N. (2002). Screening of plant extracts for antioxidant activity: a comparativestudy on three testing methods. Phytochemical Analysis. 13:8–17.

Kornsteiner, M., Wagner, K. H., and Elmadfa, I. (2006). Tocopherols and totalphenolics in 10 different nut types, Food Chemistry. 98:381–387.

Kris-Etherton, P. M., Hecker, K. D., Bonanome, A., Coval, S. M., Binkoski, A.E., Hilpert, K. F., Griel, A.E., and Etherton, T. D. (2002). Bioactive compoundsin foods: Their role in the prevention of cardiovascular disease and cancers.Am. J. Med. 113(9B):71S-88S.

Kris-Etherton, P. M., Yu-Poth, S., Sabate, J., Ratcliffe, H. E., Zhao, G., and Ether-ton, T. D. (1999). Nuts and their bioactive constituents: effects on serum lipidsand other factors that affect disease risk. Am. J. Clin. Nutr. 70(suppl):504S-511S.

Kris-Etherton, P. M., Zhao, G., Binkoski, A. E., Coval, S. M., and Etherton,T. D. (2001). The effect of nuts on coronary heart disease risk. Nutr. Rev.59(4):103–111.

Kroon, P., and Williamson, G. (2005). Polyphenols: dietary components withestablished benefits to health? J. Sci. Food Agric. 85:1239–1240.

Ku, K. L., Chang, P. S., Cheng, Y. C., and Lien, C. Y. (2005). Production of stil-benoids from the callus of Arachis hypogaea: A novel source of the anticancercompound piceatannol. J. Agric. Food Chem. 53:3877–3881.

Kuo, J. M., Yeh, D. B., and Pan, B. S. (1999). Rapid photometric assay evaluatingantioxidant activity in edible plant material. J. Agric. Food Chem. 47:3206–3209.

Lambert, J. D., Hong, J., Yang, G., Liao, J., and Yang, C. S. (2005). Inhibitionof carcinogenesis by polyphenols: evidence from laboratory investigations.Am. J. Clin. Nutr. 81(suppl):284S–291S.

Lazarus, S. A., Adamson, G. E., Hammerstone, J. F., and Schmitz, H. H.(1999). High performance liquid chromatography/Mass spectrometry anal-ysis of proanthocyanidins in foods and beverages. J. Agric. Food Chem.47:3693–3701.

Lee, S. C., Jeong, S. M., Kim, S. Y., Park, H. R., Nam, K.C., and Ahn, D. U.(2006). Effect of far-infrared radiation and heat treatment on the antioxidantactivity of water extracts from peanut hulls. Food Chemistry 94(4):489–493.

Lee, S. C., Kim, J. H., Jeong, S. M., Kim, D. R., Ha, J. U., Nam, K. C., and



Ahn, D. U. (2003). Effect of far-infrared radiation on the antioxidant activityof rice hulls. J. Agric. Food Chem. 51:4400–4403.

Lee, S. S., Lee, S. M., Kim, M., Chun, J., Cheong, Y. K., and Lee, J. (2004).Analysis of trans-resveratrol in peanuts and peanut butters consumed in Korea.Food Res. Inter. 37:247–251.

Liu, C. T., Wu, C. Y., Weng, Y. M., and Tseng, C. Y. (2005). Ultrasound-assistedextraction methodology as a tool to improve the antioxidant properties ofherbal drug Xiao-chia-hu-tang. J. Ethnopharmacology. 99:293–300.

Lou, H., Yamazaki, Y., Sasaki, T., Uchida, M., Tanaka, H., and Oka. S. (1999).A-type proanthocyanidins from peanut skins. Phytochemistry. 51:297–308.

Lou, H., Yuan, H., Ma, B., Ren, D., Ji, M., and Oka, S. (2004). Polyphenolsfrom peanut skins and their free radical-scavenging effects. Phytochemistry.65:2391–2399.

Lou, H., Yuan, H., Yamazaki, Y., Sasaki, T., and Oka, S. (2001). Alkaloids andflavonoids from peanut skins. Planta Medica. 67:345–349.

Louis, R. (1999). Masquelier’s OPC aids heart and immune system, WellBeing Journal, 8:1–3. http://www.wellbeingjournal.com/opc.htm [Accessed12/17/2006].

Lu, Y., and Foo, L. Y. (1999). The polyphenols constituents of grape pomace.Food Chemistry. 65:1–8.

Maguire, L. S., O’Sullivan, S. M., Galvin, K., O’Connor, T. P., and O’Brien, N.M. (2004). Fatty acid profile, tocopherol, squalene and phytosterol contentof walnuts, almonds, peanuts, hazelnuts and the macadamia nut. Int. J. FoodSci. Nutr. 55:171–178.

Manach, C., Scalbert, A., Morand, C., Remesy, C., and Jimenez, L. (2004).Polyphenols: food sources and bioavailability. Am. J. Clin. Nutr. 79:727–747.

Manach, C., Williamson, G., Morand, C., Scalbert, A., and Remesy, C. (2005).Bioavailability and bioefficiency of polyphenols in humans. I. Review of 97bioavailability studies. Am. J. Clin. Nutr. 81(suppl):230S–242S.

Mason, T. J. (1998). Power ultrasound in food processing – the way forward.In: Povey, M.J.W., and Mason, T. J., Eds. Ultrasound in Food Processing.London: Blackie Academic & Professional, 105–126.

Mastrocola, D., and Munari, M. (2000). Progress of the Maillard reaction andantioxidant action of Maillard reaction products in preheated model systemsduring storage, J. Agric. Food Chem. 48:3555–3559.

Mazur, W. (1998). Phytoestrogen content in foods. Bailliere’s Clinical En-docrinology and Metabolism. 12:729–742.

Mazur, W. M., Dukem J. A., Wahala, K., Rasku, S., and Adlercreutz, H. (1998).Isoflavonoids and lignans in legumes: Nutritional and health aspects in hu-mans. Nutr. Biochem. 9:193–200.

Moreno, D. A., Nebojsa, I., Poulev, A., and Raskin, I. (2006). Effects of Arachishypogaea nutshell extract on lipid metabolic enzymes and obesity parameters.Life Sciences. 78:2797–2803.

Moure, A., Cruz, J. M., Franco, D., Dominguez, J. M., Sineiro, J., Dominguez,H., Nunez, M. J., and Parajo, J. C. (2001). Natural antioxidants from residualsources. Food Chemistry. 72:145–171.

Namiki, M., Yamashita, K., and Osawa, T. (1993). Food-related antioxidantsand their activities in vivo. In: Yagi, K. Ed. Active Oxygens, Lipid Peroxidesand Antioxidants. Boca Raton: CRC Press, 319–332.

Nepote, V., Grosso, N. R., and Guzman, C. A. (2000). Antioxidant activity ofmethanolic extracts from peanut skin. Molecules 5(??):487–488.

Nepote, V., Grosso, N. R., and Guzman, C. A. (2002). Extraction of antioxidantcomponents from peanut skins. Grasas y Aceites. 53(4):391–395. Available:http://web5.silverplatter.com/webspirs/showFullRecordContent.ws [Ac-cessed 10/3/2003].

Nepote, V., Grosso, N. R., and Guzman, C. A. (2004a). Radical scavengingactivity of extracts of Argentine peanut skins (Arachis hypogaea) in relationto its trans-resveratrol content. J. Argentine Chem. Soc. 92:41–49.

Nepote, V., Grosso, N. R., and Guzman, C. A. (2005). Optimization of extractionof phenolic antioxidants from peanut skins. J. Sci. Food Agric. 85:33–38.

Nepote, V., Mestrallet, M. G., and Grosso, N. R. (2004b). Natural antioxidanteffect from peanut skins in honey-roasted peanuts. J. Food Sci. 69:S295–S300.

Normen, A. L., Brants, H. A. M., Voorrips, L. E., Andersson, H. A., van denBrandt, P. A., and Goldbohm, R. A. (2001). Plant sterol intakes and colorectal

cancer risk in the Netherlands: Cohort study on diet and cancer. Am. J. Clin.Nutr. 74:141–148.

O’Connell, J. E., and Fox, P. F. (2001). Significance and applications of phenoliccompounds in the production and quality of milk and dairy products: a review.International Dairy Journal. 11:103–120.

O’Keefe, S. F., and Wang, H. (2006). Effects of peanut skin extract on qualityand storage stability of beef products. Meat Science. 73:278–286.

O’Keefe, S. F., Felton, D. O., and Reed, K. A. (2003). Antioxidant effects ofpeanut skin and hull extracts, Abst#29B-8, 2003 IFT Annual Meeting.

Obon, J. M., Castellar, M. R., Cascales, J. A., and Fernandez-Lopez, J. A. (2005).Assessment of the TEAC method for determining the antioxidant capacity ofsynthetic red food colorants. Food Res. Inter. 38(8-9):843–845.

Ohr, L. M. (2003). Fats for healthy living. Food Technology. 57(7):91–96.

Oil, peanut, salad or cooking. USDA Nutrient database for standard reference,Release 19, http://www.nal.usda.gov/fnic/foodcomp/cgi-bin/list nut edit.pl[Accessed 1/31/2007].

Olas, B., and Wachowicz, B. (2002). Resveratrol and vitamin C as antioxidantsin blood platelets. Thrombosis Research. 106:143–148.

Peanut Institute. (2000). Peanuts contain a phytosterol thought to in-hibit cancer and help the heart, http://www.peanut-institute.org/06-29-00 Phytosterol PR.html [Accessed on 6/9/2005].

Peanuts, all types, dry roasted, without salt. USDA Nutrient database forstandard reference, Release 19. http://www.nal.usda.gov/fnic/foodcomp [Ac-cessed 1/31/2007].

Pendse, R., Rao, A. V. R., and Venkataraman, K. (1973). 5,7-dihydroxychromonefrom Arachis hypogoea shells. Phytochemistry. 12:2033–2034.

Pennington, J. A. T. (2002). Food composition databases for bioactive foodcomponents. J. of Food Composition and Analysis. 15:419–434.

Percival, M. (1997). Phytonutrients and detoxification, Clinical NutritionInsights,5(2):1–4.

Peschel, W., Sanchez-Rabaneda, F., Diekmann, W., Plescher, A., Gartzia, I.,Jimenez, D., Lamuela-Raventos, R., Buxaderas, S., and Codina, C. (2006).An industrial approach in the search of natural antioxidants from vegetableand fruit wastes. Food Chemistrys. 97:137–150.

Pietta, P. G. (2000). Flavonoids as antioxidants. J. Nat. Prod. 63:1035–1042.Pignatelli, P., Pulcinelli, F. M., Celestini, A., Lenti, L., Ghiselli, A., Gazzaniga,

P. P., and Violi, F. (2000). The flavonoids quercetin and catechin synergisti-cally inhibit platelet function by antagonizing the intracellular production ofhydrogen peroxide. Am. J. Clin. Nutr. 72:1150–1155.

Piironen, V., Lindsay, D. G., Miettinen, T. A., Tovio, J., and Lampi, A. M. (2000).Plant sterols: biosynthesis, biological function and their importance to humannutrition. J. Sci. Food Agric. 80:939–966.

Pratt, D. E., and Miller, E. E. (1984). A flavonoid antioxidant in Spanish peanuts.JAOCS. 61:1064–1067.

Prior, R. L., and Cao, G. (1999). In vivo total antioxidant capacity: Comparisonof different analytical methods. Free Radical Biology and Medicine, 27(11–12):1173–1181.

Prior, R. L., and Gu, L. (2005). Occurrence and biological significance of proan-thocyanidins in the American diet. Phytochemistry. 66(18):2264–2280.

Prior, R. L., Hoang, H., Gu, L., Wu, S., Bacchiocca, M., Howard, L., Hampsch-Woodill, M., Huang, D, Ou, B., and Jacob, R. (2003). Assays for hydrophilicand lipophilic antioxidant capacity (oxygen absorbance capacity (ORACFL))of plasma and other biological and food samples. J. Agric. Food Chem.51:3273–3279.

Prior, R. L., Wu, X., and Schaich, K. (2005). Standardized methods for thedetermination of antioxidant capacity and phenolics in foods and dietary sup-plements. J. Agric. Food Chem. 53:4290–4302.

Rajalakshmi, D., and Narasimhan, S. (1996). Food antioxidants: Sources andmethods of evaluation. In: Madhavi, D. L. Ed. Food Antioxidants: Techno-logical, Toxicological, and Health Perspectives. New York: Marcel Dekker,Inc., 65–148.

Rasmussen, S. E., Frederiksen, H., Krogholm, K. S., and Poulsen, L. (2005).Dietary proanthocyanidins: Occurrence, dietary intake, bioavailability, andprotection against cardiovascular disease. Mol. Nutr. Food Res. 49:159–174.



Re, R., Pellegrini, N., Proteggente, A., Pannala, A., Yang, M., and Rice-Evans,C. (1999). Antioxidant activity applying an improved ABTS radical cationdecolorization assay. Free Radical Biology and Medicine. 26(9–10):1231–1237.

Rehman, Z. U. (2003). Evaluation of antioxidant activity of methanolic extractfrom peanut hulls in fried potato chips. Plant Foods for Human Nutrition.58:75–83.

Ren, W., Qiao, Z., Wang, H., Zhu, L., and Zhang, L. (2003). Flavonoids: promis-ing anticancer agents. Medicinal Res. Rev. 23(4):519–534.

Rice-Evans, C. A., Miller, N. J., and Paganga, G. (1997). Antioxidant propertiesof phenolic compounds. Trends in Plant Science. 2(4):152–159.

Robbins, R. J. (2003). Phenolic acids in foods: An overview of analytical method-ology. J. Agric. Food Chem. 51:2866–2887.

Rudolf, J. L., and Resurreccion, A. V. A. (2006). Elicitation of resveratrolin peanut kernels by application of abiotic stresses. J. Agric. Food Chem.53:10186–10192.

Rudolf, J. L., and Resurreccion, A. V. A. (2007). Optimization of trans-resveratrol concentration and sensory properties of peanut kernels by slicingand ultrasound treatment, using response surface methodology. J. Food Sci.72:5450–5462.

Sampson, L., Rimm, E., Hollman, P. C. H., de Vries, J. H. M., and Katan, M. B.(2002). Flavonol and flavone intakes in US health professionals. J. Am. Diet.Assoc. 102:1414–1420.

Sanders, T. H., and Mixon, A. C., (1979). Effect of peanut tannins on percent seedcolonization and in vitro growth by Aspergillus parasiticus. Mycopathologia.66:169–173. http://www.springerlink.com [Accessed on 5/4/2006].

Sanders, T. H., McMichael, R.W., and Hendrix, K. W., Occurrence of resveratrolin edible peanuts, J. Agric. Food Chem. (2000) 48:1243–1246.

Sang, S., Lapsley, K., Jeong, W. S., Lachance, P. A., Ho, C.T., and Rosen, R.T. (2002). Antioxidative phenolic compounds isolated from almond skins(Prunus amygdalus Batsch). J. Agric. Food Chem. 50: 2459–2463.

Scalbert, A., and Williamson, G. (2000). Dietary intake and bioavailability ofpolyphenols. J. Nutr. 130:2073S–2085S.

Scalbert, A., Johnson, I. T., and Saltmarsh, M. (2005). Polyphenols: antioxidantsand beyond. Am. J. Clin. Nutr. 81(suppl):215S–217S.

Seo, A., and Morr, C. V. (1985). Activated carbon and ion exchange treatmentsfor removing phenolics and phytate from peanut protein products. J. FoodSci. 50:262–263.

Seo, S. J., Lee, S. S., Chun, J., Lee, H. B., and Lee, J. (2005). Optimization forthe post-harvest induction of trans-resveratrol in raw peanuts, Abst# 99B-31,2005 IFT Annual Meeting, 15–20, New Orleans, Louisiana.

Shi, J., Nawaz, H., Pohorly, J., Mittal, G., Kakuda, Y., and Jiang, Y. (2005).Extraction of polyphenolics from plant material for functional foods – Engi-neering and technology. Food Rev. Inter. 21:139–166.

Silva, G. L., Lee, I. K., and Kinghorn, A. D., (1998). Special problems withthe extraction of plants. In: Cannell, R.J.P. Ed. Natural Products Isola-tion:Methods in Biotechnology 4, Totowa, NJ: Humana Press 343–347.

Singleton, V. L. (1985). This week’s citation classic, ISI Current Contents. 48:18.Singleton, V. L., Orthofer, R., and Lamuela-Raventos, R. M. (1999). Analysis

of total phenols and other oxidation substrates and antioxidants by means ofFolin-Ciocalteu reagent. Methods in Enzymology. 299:152–178.

Siriwardhana, S. S. K. W., and Shahidi, F. (2002). Antiradical activity of extractsof almond and its by-products, JAOCS Abstracts, Paper no. J10157 in JAOCS.79:903–908.

Sobolev, V. S., and Cole, R. J. (1999). Trans-Resveratrol content in commercialpeanuts and peanut products. J. Agric. Food Chem. 47: 1435–1439.

Sobolev, V. S., and Horn, B. W. (2003). Phytoalexin production by the peanutplant at early stages of development, Proceedings of the 3rd Fungal Genomics,4th Fumonisin, and 16th Aflatoxin Elimination Workshops, October 13–15,Savannah, Georgia.

Sobolev, V.S., and Cole, R. J. (2003). Note on utilization of peanut seed testa.J. Sci. Food Agri. 84:105–111.

Stevanato, R., Fabris, S., and Momo, F. (2004). New enzymatic method for thedetermination of total phenolic content in tea and wine. J. Agric. Food Chem.52:6287–6293.

Suszkiw, J. (1999). Activated carbons in a nutshell, Agri. Res. 9:14–16.

Talcott, S. T., Duncan, C. E., Pozo-Insfran, D. D., and Gorbet, D. W. (2005a).Polyphenolic and antioxidant changes during storage of normal, mid, andhigh oleic acid peanuts. Food Chemistry. 89:77–84.

Talcott, S. T., Passeretti, S., Duncan, C. E., and Gorbet, D. W. (2005b). Polyphe-nolic content and sensory properties of normal and high oleic acid peanuts.Food Chemistry. 90:379–388.

Tokusoglu, O., Unal, M.K., and Yemis, F. (2005). Determination of the phy-toalexins resveratrol (3,5,4′-trihydroxystilbene) in peanuts and pistachiosby high-performance liquid chromatographic diode array (HPLC-DAD) andgas chromatography-mass spectrometry (GC-MS). J. Agric. Food Chem.53:5003–5009.

Tomas-Barberan, F. A., and Clifford, M. N. (2000a). Dietary hydroxybenzoicacid derivatives–nature, occurrence and dietary burden. J. Sci. Food Agric.80:1024–1032.

Tomas-Barberan, F. A., and Clifford, M. N. (2000b). Flavanones, chalcones anddihydrochalcones–nature, occurrence and dietary burden. J. Sci. Food Agric.80:1073–1080.

USDA Database for the flavonoid content of selected foods, Release 2.1.Nutrient Data Laboratory, http://www.ars.usda.gov/nutrientdata [Accessed1/31/2007].

USDA-ARS, National Programs Quality and Utilization of AgriculturalProducts. (2003). Action Plan. ARS-USDA Home Page. http://www.ars.usda.gov/research/programs/programs.htm [Accessed 06/14/2005].

Verstraeten, S. V., Hammerstone, J. F., Keen, C. L., Fraga, C. G., and Oteiza,P. I. (2005). Antioxidant and membrane effects of procyanidins dimers andtrimers isolated from peanut and cocoa. J. Agric. Food Chem. 53:5041–5048.

Vita, J. A. (2005). Polyphenols and cardiovascular disease: effects on endothelialand platelet function. Am. J. Clin. Nutr.81(suppl):292S–297S.

Waksmundzka-Hajnos, M., Petruczynik, A., Dragan, A., Wianowska, D., andDawidowicz, A. L. (2004). Effect of extraction method on the yield of Fu-ranocoumarins from fruits of Archangelica officinalis Hoffm. PhytochemicalAnalysis. 15:313–319.

Wang, C. C., Chu, C. Y., Chu, K. O., Choy, K. W., Khaw, K. S., Rogers, M. S.,and Pang, C. P. (2004). Trolox-equivalent antioxidant capacity assay versusoxygen radical absorbance capacity assay in plasma. Clin. Chem. 50(5):952–954.

Wang, K. H., Lai, Y. H., Chang, J. C., Ko, T. F., Shyu, S. L., and Chiou, R. Y.Y. (2005). Germination of peanut kernels to enhance resveratrol biosynthesisand prepare sprouts as a functional vegetable. J. Agric. Food Chem. 53:242–246.

Wu, X., Beecher, G. R., Holden, J. M., Haytowitz, D. B., Gebhardt, S. E., andPrior, R. L. (2004a). Lipophilic and hydrophilic antioxidant capacities ofcommon foods in the United States. J. Agric. Food Chem. 52:4026–4037.

Wu, X., Gu, L., Holden, J., Haytowitz, D. B., Gebhardt, S. E., Beecher, G., andPrior, R. L. (2004b). Development of a database for total antioxidant capacityin foods: a preliminary study. J. Food Composition and Analysis. 17:407–422.

Yamaguchi, F., Yoshimura, Y., Nakazawa, H., and Ariga, T. (1999). Free radicalscavenging activity of grape seed extract and antioxidants by electron spinresonance spectrometry in an H2O2/NaOH/DMSO system. J. Agric. FoodChem. 47(7):2544–2548.

Yanagimoto, K., Lee, K. G., Ochi, H., and Shibamoto, T. (2002). Antioxidativeactivity of heterocyclic compounds found in coffee volatiles produced byMaillard reaction. J. Agric. Food Chem. 50:5480–5484.

Yang, C. S., Landau, J. M., Huang, M. T., and Newmark, H. L. (2001). Inhibi-tion of carcinogenesis by dietary polyphenolic compounds. Annu. Rev. Nutr.21:381–406.

Yang, J., Halim, L., and Liu, R. H. (2005). Antioxidant and antiproliferativeactivities of common nuts. Abst# 35–5, 2005 IFT Annual Meeting, July 15-20, New Orleans, Louisiana.

Yao, L. H., Jiang, Y. M., Shi, J., Tomas-Barberan, F. A., Datta, N., Singanusong,R., and Chen, S. S. (2004). Flavonoids in food and their health benefits. PlantFoods for Human Nutrition. 59:113–122.

Ye, L., Koehler, P. E., and Eitenmiller, R. R. (2000). Sterol content of peanuts,pecans and peanut products, Abst# 14B-45, 2000 IFT Annual Meeting.



Yen, G. C., and Chuang, D. Y. (2000). Antioxidant properties of water extractsfrom Cassia tora L. in relation to the degree of roasting. J. Agric. Food Chem.(2000) 48:2760–2765.

Yen, G. C., and Duh, P. D. (1993). Antioxidative properties of methanolic extractsfrom peanut hulls. JAOCS. 70:383–386.

Yen, G. C., and Duh, P. D. (1994). Scavenging effect of methanolic extracts ofpeanut hulls on free-radical and active-oxygen species. J. Agric. Food Chem.42:629–632.

Yen, G. C., and Duh, P. D. (1995). Antioxidative activity of methanolic extractsof peanut hulls from various cultivars. JAOCS Abstracts 72:1065–1067.

Yen, G. C., and Hsieh, C. L. (2002). Inhibitory effects of Du-zhong (Eucommiaulmoides Oliv.) against low-density lipoprotein oxidative modification. FoodChemistry. 77:449–456.

Yen, G. C., Duh, P.D., and Tsai, C. L. (1993). Relationship between antioxidantactivity and maturity of peanut hulls. J. Agric. Food Chem. 41:67–70.

Yen, W. J., Chang, L. W., and Duh, P. D. (2005). Antioxidant activity of peanutseed testa and its antioxidative component, ethyl protocatechuate. Lebensm.-Wiss. u.-Technol. 38:193–200.

Yilmaz, Y., and Toledo, R. (2005). Antioxidant activity of water-soluble Maillardreaction products. Food Chemistry 93:273–278.

Yu, J. Ahmedna. M., and Goktepe, I. (2005). Effects of processing methods andextraction solvents on concentration and antioxidant activity of peanut skinphenolics. Food Chemistry 90:199–206.

Yu, J., Ahmedna, M., Goktepe, I., and Dai, J. (2006). Peanut skin procyanidins:Composition and antioxidant activities as affected by processing. J. of FoodComposition and Analysis. 19:364–371.


'Functional Components in Peanuts

Documents

Transcript of 'Functional Components in Peanuts