House-Keeping Items

Today (15th): Toxicology and Phytochemistry Mail your 2009 income tax return!

Tuesday (20th): Beverages and FermentationsThursday (22nd): No class Tuesday (27rd): Additives, Radicals, AntioxidantsThursday (29th): Exam #3. Last class day.

Class Assignment #2 will be posted on-line TODAY.

Due date: On or before April 28th by 5 pm. Follow the directions!

Assignment Topic: Beverages Food Additives Legal Status

Food Toxicology

Food ToxicologyThe study of the nature, properties, effects, and

detection of toxic substances in food, and their impact on humans.

Early on, people were aware that some plants are poisonous and should be avoided as food.

Other plants were found to contain chemicals that have medicinal, stimulatory, hallucinatory, or narcotic effects.

The Dose Makes the Poison

Attributed to Pericles

-a Greek statesman.

“Toxic” to One….not to AnotherFood Allergens (The “Big Eight”)

Cows milk Shellfish (Crustacea) Eggs Fin fish Peanuts Soy Tree nut Wheat

For example: Celiac Disease Ingestion of wheat, barley, ryeProline-rich protein - gliadinsTriggers immune damage to small intestine Impairs absorption of nutrientsDiarrhea, bloating, weight loss, bone pain,

anemia, chronic fatigue, weakness, muscle cramps

Scombroid PoisoningAnaphylactic shockEating fish with high histamine levels

Tuna, mackerel, other pellagic fish species

Histamine from spoilage bacteria in fish Also from putrecine and cadaverine

Everyone is susceptibleSome more sensitive (allergy?) than others.

Sensitivity or Allergy to: Lactose Sulfites Strawberries (internal histamine release) Fava beans/broad beans (enzyme deficiency) Asparagus (sulfur compounds) Red wine (low levels of histamine; SO2)

Fructose intolerance Aspartame (phenylalanine) Tartarazine (FD&C Yellow #5)

MycotoxinsSubstances produced by fungi that are harmful

to animals and humans> 100,000 species of fungi> 300 mycotoxins isolated; 30 with food issuesPlant specific

Environmental Temperature Humidity Moisture Oxygen

Claviceps purpureaGrows in wet and over-wintered grains:

rye, barley, wheatSclerotia or “ergots” (Hard-packed mycelium)“Ergotism”

Convulsions and gastrointestinal symptomsErgotamine is an analogue of lysergic acid

(LSD), a glycoalkaloidVasoconstrictor that may cause hallucinationsSt. Anthony’s firePotential cause of Salem, MA witch trials, 1692.

Aspergillus flavus and A. paraciticusUniversal food contaminant

Corn, peanuts, wheat, rice, pecans, walnuts, etc

Animal carcinogen at 5 ppbHuman liver carcinogenProblem in food industry and grain handling

Harvesting, transport, storage

4 main aflatoxins: B1, B2, G1, G2 In animal feed, B1 and B2 can be converted to

M1 and M2 and secreted in milk (ie. cow or human)

Toxins formed during Food Processing We previously covered the Maillard reaction

Polycyclic aromatic hydrocarbons (benzo(a)pyrine) Carcinogenic agents in almost every model tested But excellent flavor compounds...yet remember Pericles?

Nitrite used in curing meat and fish Antimicrobial agent Reacts with myoglobin and hemoglobin to form red nitrosyl

compounds Nitrite may also react with amines to form nitrosoamines. Carcinogenic, mutagenic.

Toxins formed during Food Processing Acrylamide in foods In 2000-2002 Swedish researchers identified acrylamide

in foods and residues from human samples. Acrylamide is a neurotoxin and carcinogen. Used as:

Cement binder, plastic manufacture, waste water treatment agent, soil conditioner, thickening agent for pesticides, cosmetics, laboratory gels, etc)

Broad range of foods with significant levels of acrylamide. Foods prepared at high temperatures. Fried and baked, but not boiled. Higher in high carbohydrate foods.

Acrylamide in PotatoesAcrylamide derived from asparagine in the

presence of sugar.Carbonyl carbon in glucose facilitates the reactionAsparagine + Sugar + Heat = Acrylamide

Natural Food “Toxins” in Plants

Metabolism and Plant Primary CompoundsPlant metabolism:

Used to describe the chemical reactions and interactions that take place in a biological system.

Includes reactions that cause a plant to shift its leaves towards a light source

Cause chloroplasts to produce photosynthetic sugars from sunlight, carbon dioxide, and water, ect

Includes the production of plant primary and secondary compounds.

Plant Primary Compounds Those compounds which are formed as a part of the

normal anabolic and catabolic processes.

Plant Secondary Compounds Secondary Compounds

Those compounds that are not primary compounds. A compound that does not seem to directly function in the

processes of growth and development. Some regarded these substances as waste products of a cell. At least one major benefit a plant gains from producing

secondary compounds was later discovered: protection from certain types of herbivory.

The most obvious way to discourage this was to synthesize a substance to make the plant taste bad.

The bitter taste of tea is due to the secondary compounds found in the tea leaves (caffeine and tannins).

Other Mean Tricks Secondary Compounds

Another way to hinder herbivory was to synthesize compounds that would cause temporary or permanent physiological changes in the herbivore (Toxins)

Caffeine and morphine are good examples. Isoflavonoids affect reproduction in mammals. Found in

alfalfa, soy, and some clover species, it mimics the hormone progesterone and may cause infertility, reduced lactation, or difficulties in labor.

These types of secondary compounds make an animal "think twice" about eating off the same plant again.

Not so coincidentally, this same type of physiological effect is what people refer to as the "high" after consuming certain plants (mushrooms, nutmeg, “weed”, coffee, etc)

Do plants experience stress the way humans do?

Hypericum perforatun Lycopersicum esculentun

Causes of Plant Stress (Elicitors)

Insects (US est. at $100M annum)Weather (drought, flood, wind, hail)Ethylene (ppb levels)Post-harvest storage UV lightPhysical wounds (harvest, transport)Microbial contamination

(polysaccharides)

Results of Plant Stress

Phytoalexins (Phyto = “plant” and alexin = “to ward off”)

Low MW organic metabolites produced by plants in response to stress

“Self-made antibiotics”We consume ~10,000 times more “natural”

chemicals than man-made chemicals~150 true phytoalexins known

What? Toxic Chemicals in My Food!!Phytochemical ParadoxDangerous pesticide or antioxidant wonder??For the plant:UV light protection (Nature’s sun-screen)Oxidative protectionAnti-microbial (Anti-Herbivores?)For the consumer (us):ROS quencherBitter, astringent and sour flavors

Pre-existing defenses

Induced/Biochemical defenses

Hypersensitive responses

DEFENSE MECHANISMS

Production of phytoalexins may be stimulated by certain compounds called elicitors.

High molecular weight substances found in the cell wall such as glucans, glycoprotein, or other polysaccharides.

Gases such as ethylene (C2H4)

PRODUCTION OF PHYTOALEXINS

In susceptible plants, a pathogen may prevent the formation of phytoalexins, by the action of suppressors produced by the pathogen.

The suppressor also can be a glucan, a glycoprotein, or a toxin produced by the pathogen

PRODUCTION OF PHYTOALEXINS

Chemical and Sensory Properties of Food “Toxins”

Aromatic Sour Bitter Astringent Sulfurous Medicinal Smoky Animal-like

Metal chelator Antioxidant (-OH groups)

Free radical terminators

ROO. + AH = ROH + A.

Resonance stability

O O O O

. ..

OH

Phytoalexic Toxins In Our Food

PotatoStress MetabolitesCinnamates, scopolin, quinic acid, sesquiterpenoids,

solanine, chaconine

Solanine (Glycoalkaloid)Sunburned spuds or growth shoots (periderm)10-50 ppm is normal, increases 7-fold during stress Natural pesticide (cholinesterase inhibitor)

Acetylcholine is a neurotransmitterExtremely bitter, not soluble in waterHeat stable

TomatoStress MetabolitesCinnamates, rishitin, falcarindiol, tomatine

Tomatine (Alkaloid)High in immature fruitRipe tomato contains ~30-40 ppmNatural pesticideHeat labile

CarrotStress MetabolitesCinnamates, falcarinol, falcarindiol, isocoumarin

Isocoumarin (neutral phenolic)Anti-microbial (~10 ppm)Extremely bitter, not soluble in waterHeat stableEthylene sensitive synthesis

“Natural” Carcinogens in Coffee Acetaldehyde Benzaldehyde Benzene Benzofuran Benzo[a]pyrene Caffeic acid Catechol 1,2,5,6 Dibenzanthracene Ethanol

Ethylbenzene Formaldehyde Furan Furfural Hydrogen peroxide Hydroquinone Limonine Styrene Toluene Xylene

Other Commodities

Peppers- Capsidiol

Sweet potato- Ipomeamarone

Celery, parsnips, parsley- Psoralens (furanocoumarins)

Grapes- Resveratrol, stilbene

Alfalfa- Medicarpin (Isoflavonoid)

Soybean roots- Glyceollin

Peas- Pisatin

Bean pods- Phaseollin

Plant vs Man: “Xenobiotic” Metabolism

Cytochrome P-450 system In body: liver, lung, skin, nasal mucosa, GI tractEnzyme system to solubilize chemicalsSubstrate (xenobiotics) must be somewhat

lipophilic to reach active sites for metabolismPlants did not want to become food for people or

animals….but we fought back !!

“Antioxidant” Enzyme Systems

Active Oxygen Detoxification Enzymes SOD (superoxide dismutase) GSH (glutathione) POD (peroxidase) CAT (catalase)

Cytochrome P-450 systemInduction of Phase I and Phase II Enzymes

Phase IOxidation/Reduction– Add/Remove O, Add/Remove H.

ie. alcohol dehydrogenaseHydrolysis.– Add water

Phase IIConjugation reactions.-Enzyme catalyzed reactions.-Tend to increase size and polarity for excretion.

Phytochemicals

Current trend: Increased consumer interest in nutraceuticals…..which are phytochemicals

Nutraceuticals

Dietary compounds, foods, or supplements used to promote

health life or prevent some disease

Phytochemical

Components in a plant based diet other than traditional

nutrients that can potentially reduce the risk of degenerative diseases

Vit K and E Polyhenolic Sterols Prebiotics Probiotics

Phyto= plant…chemicals Organosulfides Isothiocynates Indoles Carotenoids Saponins Tocopherols Amino acids/Proteins Lipids Carbohydrates

Polyphenols Flavonoids Tannins Isoflavones

Vitamins/Minerals Coumarins Dietary Fiber Enzymes

Mechanisms of ActionMany antioxidant effects Increased activity of enzymes that detoxify

carcinogensEffect on cell differentiationBlock formation of carcinogens (ie. nitrosamines)Alter estrogen metabolismDecrease cell proliferationMaintenance of normal DNA repair

How Did They Get There ??

Selective Biosynthesis

How are Phytoalexins Formed?The “-noids” Shikimic acid pathway (phenylpropanoids)

Hydroxycinnamic acids Coumarins Hydroxybenzoic acids

Mevalonic acid pathway (Isoprenoids) Carotenoids Terpenoids

Combination of Pathways

(Shikimic-Polymalonic) Flavonoids and anthocyanins

OOH

OH O

OH

OH

OH

OH

HOOC

OH

OH

OOCCH CH

OH

OH

Shikimic Acid Pathway-Phenolics

PEP from glycolysis + erythrose 4-P from PP-pathway forms skikimic acid which are the precursor to phenylalanine and tyrosine.

PAL and TAL (ammonia lyases) Cinnamic acid Coumarin p-Coumaric acid Caffeic acid Ferulic acid Sinapic acid

COOHOH

COOHOH

OH

COOHOH

MeO

COOHOH

MeO

MeO

O

OH

OH

OH

OH

OH

D-glucose

O3PO

H

OOH

OH

O3PO

COO-

+

erythrose 4-phosphate phosphoenolpyruvate

O

O3POH2COH

OH

OH

COOH

deoxy-arabino-heptulosonate-7-phosphate

DAHP synthetase

OH

OH

O

OH COOH

dehydroquinatesynthase

3-dehydroquinic acid

OH

OH

O

COOH

dehydroquinatedehydratase

3-dehydroshikimic acid

OH

OH

OH OH

COOH

quinic acid

quinatedehydrogenase

OH

OH

OH

COOH

shikimic acid

NADPH NADP+

shikimatedehydrogenase OH

OH

O3PO

COOH

shikimate kinase

ATP

3-phosphoshikimic acid

ADPO3PO COOH

PEP

EPSP synthase

OH

O COOH

COOH

chorismatesynthetase

chorismic acid

The Shikimic Acid Pathway Leading to Phenylpropanoid and Flavonoid SynthesisThe Shikimic Acid Pathway Leading to Phenylpropanoid and Flavonoid Synthesis

OH

OH3OPO OH

COOH

3-phosphoquinic acid

O3PO

OH

O

HHH

OPO3

COOH

COOH O3PO

OH

O

COOH

COOH

5-enolpyruvyl shikimic acid 3-phosphate

O

COOH

COO-

NH3+H

CH2

OH H

HOOCCH

COOH

NH2

prephenatedehydratase

Phenylalanine (phe)

Phenylpyruvic acid

Arogenic acid

arogenatedehydratase

OH

COOH

HOOC

chorismatemutase

prephenic acid

OH

COOH

cinnamate-4-hydroxylase

p-coumaric acid

OH

OH COOH

Caffeic acid

p-comuarate3-mono-oxygenaseOH

MeO COOH

Ferulic acid

caffeate methyl-3-O-transferase

S-adenosyl-methionineOH

MeO

OMe

COOH

Sinnapic acid

Caffeic acid 3-O-methyltransferase

2-oxoglutaric acid glutamic acid

glutamine 2-oxoglutarateamidotransferase (GOGAT)

glutamine glutamic acid

NH4+ from PAL

COOH

L-phenylalanineammonia lyase (PAL)Cinnamic acid

NH4+

NH2

OH

COOH

arogenatedehydrogenase

NADP+

NADPH

tyrosine ammonia-lyase (TAL)

NH4+

tyrosine

OH

OH

OMe

COOH

5-hydroxyferulic acid

Ferululate-5-hydroxylase

OH

OH

OH OH

COOH

OH

OH

OO

OHOH

OH

COOH

quinic acid

Chlorogenic acid(5 cafeoylquinic acid)

OH

OH

OO

OH OH

OH COOH

OH

OH

OO

O OH

OH COOH

OHOH

O

Chlorogenic acid(4 cafeoylquinic acid)

Isochlorogenic acid(4,5 cafeoylquinic acid)

OH

OH

O

OH

OH

OO

O OH

OH

COOH

Isochlorogenic acid(3,5 cafeoylquinic acid)

COS-CoA

OH

hydroxycinnamate:CoA ligase(4-coumaroyl:CoA ligase)

p-coumaryl-CoAOH

COOH

OH

OH

CHO

OH

COOH

p-hydroxybenzaldehydep-hydroxybenzoic acid

NADP+NADPH

OH

OOH

OH

OH

Me SCoA

O

SCoA

O

HOOC

chalconesynthase

Chalcone

-3CO2

acetyl CoAcarboxylase

Malonyl CoA

O

O

OH

OH

OH

R2

R1

chalconeisomerase

Flavanone

O

OOH

OH

OH

OH

R2

R1

Dihydroflavonol

flavanone3-hydrolase

O

OOH

OH

OH

OH

R1

R2

Flavonol

flavonolsynthase

O

OOH

OH

OH

R1

R2

Flavone

flavonesynthase I & II

O

OHOH

OH

OH

OH

R2

R1

Flavan-3,4-diol(leucoanthocyanidin)

dihydroflavonol4-reductase

NADPHNADP+

O+

OH

OH

OH

OH

R2

R1

Anthocyanidin

anthocyanidinsynthase

O2 & alpha-ketoglutarate

2H2OCO2

succinateO

+

OH

OH

OH

Gly

R2

R1

Anthocyanidin-3-O-glycosides

flavonoidglucosyltransferase

UDP-D-glucose

UDP

O

OH

OH

OH

OH

R1

R2

Flav-3-nol

leucoanthocyanidinreductase

O

OHOH

OH

OH

R

Flavan-4-ol

flavanone4-reductase

R1 = R2 = H; DihydrokaempferolR1 = H, R2 =OH; Dihydroquercetin

R1 = R2 = OH; Dihydromyricetin

R1 = R2 = H; KaempferolR1 = H, R2 =OH; Quercetin

R1 = R2 = OH; Myricetin

R1 = R2 = H; LeucopelargonidinR1 = H, R2 =OH; LeucocyanidinR1 = R2 = OH; Leucodelphinidin

R1 = R2 = H; PelargonidinR1 = H, R2 =OH; CyanidinR1 = R2 = OH; Delphinidin

R1 = R2 = H; Pelargonidin-3-glycosideR1 = H, R2 =OH; Cyanidin-3-glycosideR1 = R2 = OH; Delphinidin-3-glycoside

R1 = R2 = H; AfzelechinR1 = H, R2 =OH; Catechin

R1 = R2 = OH; Gallocatechin

OOH

OH

OH

R3

R4

O

OH

OH

OH

OH

R1

R2

Procyanidins

leucoanthocyanidinreductase

R1 = OH, R2 = H; NaringeninR1 = OCH3, R2 =H; Isosakuranetin

R1 = R2 = OH; EriodictyolR1 = OCH3, R2 = OH; Hesperitin

R1 = OH, R2 = H; ApigininR1 = OCH3, R2 = H; Fortuneletin

R1 = R2 = OH; LuteolinR1 = OCH3, R2 = OH; Diosmetin R = H; Apiferol

R = OH; Luteoferol

OH

O

OH

OH

OH

chalconeisomerase

Isoliquiritigenin

chalconereductase

O

OOH

OH

OH

isoflavonesynthase

2-hydroxyisoflavanone

NADPHO2

NADP+

H2O

O

OOH

OH

OH

2-hydroxyisolflavanonedehydratase

H2O

Daidzein

O

O

OH

OH

OH

Naringenin

O

OOH

OH

OH

OH

2-hydroxyisoflavanone naringenin

isoflavonesynthase

NADPHO2

NADP+

H2O

OH

O

O

OH

isoflavonesynthase

Liquiritigenin

O

O

O

OH

o-methyltransferase

S-adenosyl-homocysteine

S-adenosyl-methionine

2,7-dihydroxy-4'-methoxyisoflavanone

O

OOH

OH

OMe

H2O

Formononetin

S-adenosyl-homocysteine

S-adenosyl-methionine

o-methyl transferase

O

OOH

OH

OHgenistein

isoflavonedehydratase

H2O

O

OOH

OH

O

OH

H

2,5,7-trihydroxy-4'-methoxyisoflavanone

isoflavonemethyl transferase

S-adenosyl-methionine

S-adenosyl-homocysteine

O

OOH

OH

OBiochinan A

methoxyisoflavonedehydratase

H2O

S-adenosyl-methionine

S-adenosyl-homocysteine

O

OOH

O

OHPrunetin

isoflaveone methyltransferase

S-adenosyl-methionine

S-adenosyl-homocysteine

O

OOH

OH

O

OH

Pratensein

isoflavonehydrolase

NADPHO2

NADP+

H2O

Flavonoids

Phenylpropanoids

OH

COOH

OH

protocatechuic acid

O2

NADP+

H2ONADPH

p-hydroxybenzoicacid hydroxylaseOH

COOH

OHOH

gallic acid

O2

NADP+

H2ONADPH

protocatechuicacid hydroxylase

Phenolics

Plants produce a variety of compounds that contain one or more phenol groups - called phenolics

Thousands of phenolics occur in plants

PhenolicsLarge group of diverse compoundsMany serve as defense compounds against

herbivores and pathogensSome attract pollinatorsSome absorb UV lightSome reduce growth of competitors

BackgroundFlavonoids are non-nutrients1936-Szent-Gyorgyi, called flavonoids Vitamin P.1950’s disproved the theoryLate seventies-mutagenecity of quercetinRecent research-anticarcinogenic

O

OH

O R2

R1

HO

HO

Structure of flavonoids

X

7

6

5

3

2

4

8

6151

41

31

21

A

B

C

FLAVONOLSKaempferolQuercetinMyrcetin

O

OH

Kaempferol

O

OH

HO

HO

O

OH

Quercetin

O OH

OH

HO

HO

O

OH

Myricetin

O

OH

HO

HO

OH

OH

Two Specific Polyphenolics

Ellagic acid

Isoflavonoids

Ellagic acid Derivatives

Ref. Mullen et.al. 2003

Ellagic acid Conversion

OOH

OOH

OH

Isoflavones share several features in common with estradiol

1. Presence of a phenolic (benzene) ring: Prerequisite for binding to the

estrogen receptors.

2. Pair of OH- groups separated by a similar distance

3. Common compounds: genestein/genestin and diadzein/diadzin

Isoflavone

CH3

OH

OH

17 - estradiol

Isoflavones: Free- and “Conjugated” Forms

OR1

OOH

OH

R2

OR1

OO

OH

R2

OCH2

HH

OHH

OHOH

H H

HOH

OR1

OO

OH

R2

OCH2

HH

OHH

OHOH

H H

HO

R3

Acetyl COCH3

Malonyl COCH2COOH

Aglycone

Glycoside

Phytochemicals

Carotenoids

Mevalonic Acid Pathway-Carotenoids

Pyruvate from glycolysis is decarboxylated to form acetate which combines with coenzyme A to form acetyl CoA.

Acetate + Acetyl CoA = Acetoacetyl CoA Acetoacetyl CoA + Acetyl CoA = Mevalonic acid

Phytoene Lycopene ß-carotene Lutein

O

COOH

H OPO3

OH

OH TPP

2-

Pyruvate

Glyceraldehyde 3-phosphate

thiaminepyrophosphate CO2

1-deoxy-D-xylulose5-phosphate synthase

The Mevalonic Acid Pathway for Carotenoid SynthesisThe Mevalonic Acid Pathway for Carotenoid Synthesis

OPO3

OHO

OPO3

OH

OH

OH

2-

1-deoxy-D-xylulose5-phosphate

NADPH + H+ NADP+

2-

2-C-methyl-D-erythriol4-phosphate

OPO3PO3

metabolitesunknown Isopentyl

diphosphate (IPP)

OPO3PO3

Dimethallylpyrophosphate

IPP Isomerase

OPO3PO3

OPO3PO3

Farnesyldiphosphate (FPP)

IPP Isomerase

Geranyldiphosphate (GPP)

IPP Isomerase

OPO3PO3

Geranylgeranyl diphosphate (GGPP)

IPPIsomerase

Prephytoene pyrophosphate

phytoenesynthase

Phytoene

phytoenesynthase

Phytofluene

phytoenedesaturase

Zetacarotene

zetacarotenedesaturase

Neurosporene

phytoenedesaturase

Lycopene

zetacarotenedesaturase

Delta-carotene

lycopene epsilon cyclase

Gamma-carotene

lycopene beta cyclase

Alpha-carotene

lycopene beta cyclase

Beta-carotene

lycopene beta cyclase

OH

Zeinoxanthin

beta-carotene hydrolasee

OH Beta-cryptoxanthin

beta-carotene hydrolase

OH

OH Lutein

alpha-carotenehydrolase

OH

OH Zeaxanthin

beta-carotene hydrolase

caroteneisomerase

Nomenclature and Structure

OH Beta-Cryptoxanthin

LuteinOH

OH

Beta-Carotene

Metabolism of Dietary Carotenoids

Breeding Fruits and Vegetables for Functionality

Phytochemicals for Improved Human Health

Crops containing or that can be developed with: Anthocyanins Carotenes Phenolic acids Quercetin Vitamins C, D, and E

Blueberry Antioxidants

Blackberry Antioxidants

Total Soluble Phenolics and ORACTotal Soluble Phenolics and ORAC

0

1500

3000

4500

6000

7500

0 20 40 60 80 100 120 140

ORAC (µM Trolox equivalents)

Tot

al P

heno

lics

(mg/

kg C

hlor

ogen

ic a

cid)

Blueberry (9)Blackberry (13)

Grape (10)Peach-Nectar. (10)Tomato (10)

R2 = 0.62

Anthocyanins and ORACAnthocyanins and ORAC

0

400

800

1200

1600

2000

0 20 40 60 80 100 120 140

ORAC (µM Trolox equivilents)

Ant

hocy

anin

(mg/

kg M

alvi

din

3-G

lu)

Blackberry (13)Blueberry (9)Grape (4)Nectarine (1)

R2 = 0.51

Structure-Based Antioxidant Activity of Phytochemicals

p-OH-benzoicp-coumaric

ProtocatechuicCaffeic

VanillicFerulic

0.08 2.22

1.19 1.26

1.43 1.90

Structurally Similar Compounds

OOH

OH O

OH

OH

OH

OOH

OH

OH

OH

OH

OOH

OH

OH

OH

OH

+

QuercetinAOX = 4.7

CatechinAOX = 2.4

CyanidinAOX = 4.4

Importance of the 3-OH group

OOH

OH O

OH

OH

OH

OO

O

OO

O

OOH

OH O

OH

OH

QuercetinAOX = 4.7

Quercetin-3-glucosideAOX ~ 2.5

OOH

OH O

OH

OH

LuteolinAOX = 2.1

Importance of the 2-3 db

OOH

OH O

OH

OH

OH

QuercetinAOX = 4.7

TaxifolinAOX = 1.9

OOH

OH O

OH

OH

OH

Summation

OOH

OH O

OH

OH

OH

QuercetinAOX = 4.7

OOH

OH O

OH

OH

Rutinoside

OOH

OH O

OH

OH

OOH

OH O

OH

OH

OOH

OH O

OH

OH

OH

RutinAOX = 2.4

KaempferolAOX = 1.3

LuteolinAOX = 2.1

TaxifolinAOX = 1.9