Flower Extracts and Their Essential Oils as Potential Antimicrobial Agents for Food Uses and...

Flower Extracts and Their Essential Oilsas Potential Antimicrobial Agents for FoodUses and Pharmaceutical ApplicationsHan Ching Voon, Rajeev Bhat, and Gulam Rusul

Abstract: Plants with potential therapeutic value have been used from time immemorial to cure various ailments andinfectious diseases. Secondary metabolites or the bioactive compounds (phytochemicals) present in plants have beenreported to be accountable for various observed biological activities. Consumer awareness of the possible side effects ofusing chemical-based antimicrobial agents has forced researchers to identify and explore natural plant-based antimicrobialagents (or preservatives) that are toxicologically safe, especially when used in food applications. Of late, scientific evidencehas been provided on the potential antimicrobial activities exhibited by certain traditionally used flower extracts or theiressential oils (edible and wild). This review focuses on providing and updating available information on the antimicrobialactivities exhibited by flowers, which are envisaged to find potential applications as natural preservatives for foods orapplications in the pharmaceutical industries to develop new and economical herbal-based products for treating variousdiseases.

IntroductionInfectious diseases and foodborne illnesses can cause severe

health effects and can even lead to death among the residingpopulation, especially in the developing regions of the world.The continual emergence of antibiotic-resistant microorganismshas prompted researchers’ world over to search for new antimicro-bial agents that are more effective against the resistant microbialpathogens (Nascimento and others 2000; Thaller and others 2010).Structural modification of the antimicrobials (against which mi-crobial resistance has been developed) is reported to improve theeffectiveness of antimicrobial agents against bacteria, fungi, andviruses (De Clercq 2001; Poole 2001; Jeu and others 2003; Zhangand others 2010). However, of late, research efforts have beenput forth to improve the effectiveness of antimicrobial drugs bydeveloping novel and a new class of antimicrobial drugs that caneffectively work on multitargeted sites or organisms (Esterhuizenand others 2006; Alka and others 2010).

Traditionally, plants with potential therapeutic or medicinal val-ues have been successfully utilized for preventing and treating var-ious ailments and foodborne illnesses. Since time immemorial,various plants and their products have been used in traditionalmedicine to cure some of the common disorders and degenerativediseases in humans as well as in animals (such as Ayurvedic and tra-ditional Chinese medicinal practices). The effectiveness of these

MS 20110898 Submitted 7/26/2011, Accepted 9/26/2011. Authors arewith Food Technology Div., School of Industrial Technology, Univ. SainsMalaysia, Penang 11800, Malaysia. Direct inquiries to author Bhat (E-mail:[email protected] and [email protected]).

procedures has been attributed mainly to the presence of activephytochemicals or bioactive compounds in plants (Quarenghi andothers 2000; Ye and others 2004; Zhang and Zhang 2007; Dungand others 2008; Zhao and others 2009).

Given the scope of searching new antimicrobial agents, antimi-crobials derived from plant materials are often regarded as naturaland safe compared to industrial chemicals. Of late, plant-basedmedicine has become more popular due to the increasing concernof consumers with regard to the use of synthetic chemical prepa-rations and use of artificial antimicrobial preservatives, especiallyin modern food protection practices (Marino and others 2001;Hamedo and Abdelmigid 2009).

Some of the hoped-for advantages of using natural antimicro-bials include: reducing total dependence on antibiotics, reducingdevelopment of antibiotic resistance by pathogenic microorgan-isms, controlling cross-contaminations by foodborne pathogens,improvizing food preservation technology, and strengthening im-mune system in humans (Abou-taleb and Kawai 2008; Fisherand Phillips 2008; Tajkarimi and others 2010). Today, growingmarket trends indicate a rapid increase in the number of natu-ral plant-derived products (such as green tea, herbal decoctions,or herbal medicines) that may include aerial parts, seeds, fruits,roots, rhizomes, and flowers. Among these, flowers have attainedhigh priority and found various applications. Floral extracts andtheir isolated essential oils are traditionally believed to be rich inphytochemicals exhibiting rich bioactivity. These compounds areof interest to the local industry as well as to the general pop-ulation and are actively being explored for various commercialapplications (such as tea, bakery products, and more). Floral ex-tracts and essential oils are also considered to be potential natural

34 Comprehensive Reviews in Food Science and Food Safety � Vol. 11, 2012c© 2011 Institute of Food Technologists

doi: 10.1111/j.1541-4337.2011.00169.x

Flowers as potential antimicrobial agents . . .

antimicrobial agents. Available reports indicate their efficacy andto possess a broad spectrum of antimicrobial activity against vari-ous spoilage and pathogenic microorganisms, which is attributedto their bioactive constituents (Quarenghi and others 2000;Ye and others 2004; Zhang and Zhang 2007; Dung and others2008; Zhao and others 2009). Based on these facts, the present re-view focuses mainly on providing baseline information on explor-ing some of the common and wild (edible and nonedible) flowerspossessing potential antimicrobial activities. The details on theseaspects are hopefully expected to be useful for the commercial ex-ploitation of flowers to develop natural preservative preparationswith applicability in the food and pharmaceutical industries.

Extraction MethodSolvent extraction

Solvent extraction is one of the most widely employed methodsfor preparation of flower extracts. Solvent extraction (solid-liquidextraction) involves the process of leaching (simple physical so-lution or dissolution process). Leaching is a separation techniquethat involves removal of soluble solids from a solid mixture byemploying a suitable solvent or solvent mixture. Various factorsinfluence the solvent extraction procedure, which includes: therate of transport of solvent into the material, rate of solubilizationof soluble constituents in the solvent, and the rate of transportof solution (extract) out of the insoluble matter. Solvent polarity,vapor pressure, and viscosity are also of importance for effectiveextraction. In case of plant materials, adequate time is required fordiffusion of solvent via plant cell walls for dissolution of solubleconstituents and for diffusion of the solution (extract) out to thesurface of the cell wall (Houghton and Raman 1998; Singh 2008;Wijekoon and others 2011).

Flower extracts can be prepared either from fresh or dried sam-ples. Prior to extraction, flower samples are subjected to air-dryingor freeze-drying, followed by grinding, milling, or homogeniza-tion to reduce sample particle size. These procedures are followedin order to enhance the efficiency of extraction process and yield ofthe resulting extract. Various solvents, such as methanol, ethanol,hexane, acetone, ethyl acetate, chloroform are commonly used forextraction (either in the pure form or after dilution with distilledwater) (Dai and Mumper 2010). Choice of selecting a solventmainly depends on the solubility of the bioactive constituents,safety aspects, and potentials involved for artifact formations (Jonesand Kinghorn 2005). Maintaining the stability of bioactive com-pounds is vital while selecting an appropriate and efficient ex-traction method as some of the compounds (mainly those ofphenolics) tends to get oxidized and degraded at high temper-ature or on prolonging the extraction time (Robards 2003; Daiand Mumper 2010). Besides, an optimized value of “sample-to-solvent” ratio needs to be standardized, which involves equilibriumbetween avoidance of saturation effects, solvent wastes, and costsincurred (Pinelo and others 2006; Dai and Mumper 2010). Mag-netic stirring and continuous rotary shaking are also employedin certain cases to enhance molecular interactions during extrac-tion process. Usually, to ensure maximum extraction of bioactivecompounds, the extraction process is repeated 2 or 3 times andthe extracts are pooled together (Guillen and others 1996; Stalikas2007). Followed by this, the extracts are filtered and centrifugedto remove any floating particulate matters. In order to prevent for-mation of artifacts and degradation or polymerization of phenoliccompounds, flower extract should not be stored in the solvent atroom temperature or exposed to direct sunlight for a long timeduration. Once done, extracts are freeze dried or concentrated

at reduced pressure (temperature preferably ≤ 40 ◦C) in a rotaryevaporator to prevent degradation of heat-sensitive compounds.

Solvent extractions are classified into 2 methods: continuousand noncontinuous. In continuous extraction method (such aspercolation, soxhlet extraction), solvent flow through the samplecontinuously and the saturated solvent is constantly replaced witha less saturated solvent. In noncontinuous method (such as mac-eration, infusion, decoction), the extraction is stopped when asuitable equilibrium is reached between the solute concentration(inside the flowers and the solvent), unless the solvent needs to bereplaced with a new batch of solvent (Jones and Kinghorn 2005).

Percolation. This is an efficient method wherein a percolatoris used for extraction. Percolator is comprised of a wide opening(at the top) to accommodate addition or removal of a samplealong with a valve at the bottom, designed to allow outflow ofthe solvent. With the valve held at a closed position, samples inpowdered form are added and packed into the percolator leavingsufficient space to allow expansion. Then the samples are coveredby addition of a suitable solvent, and are allowed to soak for fewhours or overnight. Further, the solvent is allowed to flow out ata controlled flow rate from the bottom of the percolator throughthe valve. Fresh solvent is added at the top to replace the saturatedsolvent “flow-out” from the percolator (Jones and Kinghorn 2005;Singh 2008).

Soxhlet extraction. Soxhlet extraction is a common conven-tional method used for extracting heat-stable compounds. TheSoxhlet extractor consists of a distillation flask, an extractor, anda condenser. The solvent in the distillation flask is heated and theresulting vapor is condensed in the condenser. The condensed sol-vent from the condenser fills into the thimble-holder containingthe sample that needs to be extracted. When the solution in theextractor reaches the overflow level, a siphon aspirates the solutionof the thimble-holder and unloads it back into the distillation flask,carrying dissolved solute into the bulk liquid. The solute is left inthe distillation flask while the solvent is evaporated, condensed,and passed back into the sample solid bed. This process is repeated3 to 5 times or until a complete extraction is achieved (Tandonand Rane 2008).

Maceration. This method is routinely employed in the labswherein a conical flask covered with aluminum foil or parafilm isused to prevent evaporation of the solvent to avoid batch to batchvariations. The powdered sample is left to macerate for a knownperiod after addition of a suitable solvent. The maceration processis considered to be rather slow, and sometimes requires occasionalor continuous shaking (or stirring), as it works by molecular dif-fusion. Occasional shaking ensures dispersal of saturated solutionaround the particle surface, bringing fresh solvent to the surface ofparticle for further extraction. After maceration, the extract is fil-tered through an appropriate filter or screen. In certain instances,the solid residues are pressed and the occluded solutions are pooledwith the extract before filtration (Jones and Kinghorn 2005; Singh2008).

Infusion. Infusion is a dilute solution that contains readily solu-ble constituents prepared by short period of maceration (steeping)of sample in cold or boiling water. Cold water is recommendedto be used for extraction of heat-sensitive compounds. It is highlycrucial to dispense the infusion within 12 h of its preparation as itis liable for microbial contamination (Singh 2008).

Decoction. Decoction is the most widely used and popular tra-ditional method for the preparation of aqueous extracts of medic-inal plants. It is made by boiling the sample in water for a periodof fixed time duration (Tandon and Rane 2008).

c© 2011 Institute of Food Technologists Vol. 11, 2012 � Comprehensive Reviews in Food Science and Food Safety 35


Extraction of Essential OilsHydrodistillation is the simplest and oldest method for obtaining

essential oils from plants. In this method, samples are packed in adistillation unit with addition of water. This is brought to a boilby applying mild heat (water distillation); alternatively, live steamis injected into the sample (direct steam distillation). Essential oilsare liberated from oil glands present in the plant tissues (due toeffects of hot water and steam). The vapor mixture of water and oilis condensed, when it is carried over to the condenser. From thecondenser, the distillate flows into a separator, where the essentialoil is separated automatically from the distillate water. Laboratory-scale isolation of essential oil from flowers is accomplished byhydrodistillation with a Clevenger apparatus. In this method, waterdistillation is used wherein samples loaded in the apparatus arecompletely immersed in water, and brought to a boil (Handa2008).

However, there are also other physical methods that are used inconjunction with these methods, such as ultrasound treatments,radiation treatments (UV, Gamma, or electron beams), supercriti-cal carbon dioxide extraction and others, which have been foundto be beneficial for better extraction of bioactive compounds.

Methods for determining antimicrobial activity of floralextracts and essential oils

Various conventional methods are routinely employed for de-termining the antimicrobial activity of floral extracts and essentialoils. Generally, in vitro assays are employed. The agar diffusionmethod (paper disc or well) and dilution method (agar or broth)are the 2 most common techniques used.

Agar diffusion method. The agar diffusion method is one ofthe most widely employed techniques for evaluating antimicro-bial activity. In this technique, agar plates are inoculated with testmicroorganisms (usually pathogenic microbes). Floral extracts oressential oils are applied directly onto paper discs, which are thenplaced on the agar medium or into wells made in the agar. Theagar plates are incubated to allow the components of floral extractsor essential oils to diffuse into the agar medium. The diameter ofgrowth inhibition zones around the discs or wells is then consid-ered to be an indication of the effectiveness of the material beingtested (Kalemba and Kunicka 2003; Holley and Patel 2005).

Dilution method. In this method, agar broth cultures (in Petridishes or test tubes) and liquid broth cultures (in conical flasks ortest tubes or by microtiter plate-broth microdilution method) areused for determining antimicrobial activities. The inhibitory effectof the extracts or essential oils are measured based on turbidimetryor the plate count method. The obtained result is expressed asgrowth inhibition index (percentage growth inhibition comparedto the control cultures without extract or essential oil) or minimuminhibitory concentration, MIC (lowest concentrations of extractor essential oil that can inhibit the growth of microorganisms).In some of the reports (Dung and others 2008; Abdoul-Latif andothers 2010) minimum lethality concentration (MLC, the lowestconcentration of extract or essential oil that kills or totally inhibitsa microorganism), minimum bactericidal concentration (MBC)or minimum fungicidal concentration (MFC) is computed. Themicroorganisms from agar broth or liquid broth where no growthoccurs are observed and are transferred into a new medium andincubated for a certain fixed period of time. In some instances,MLC is considered to be a concentration that leads to >99.9%reduction in the number of microorganisms originally inoculated(Kalemba and Kunicka 2003; Holley and Patel 2005).

Floral Extracts and Their Essential Oils with Antimi-crobial Activities

In Table 1, an overview is presented on some of the selectedreports on edible flowers exhibiting antimicrobial activities. Aschematic representation on the potential uses of edible flow-ers, their antimicrobial activities, and their applications as naturalantimicrobial agents is depicted in Figure 1. Additionally, somecommon flowers with reported antimicrobial activities are shownin Figure 2. In the text below, the potential antimicrobial activitiesexhibited/reported on some floral extracts (in solvents) and theiressential oil is discussed.

Allium speciesAllium spp. belongs to the largest genus (Allium, Alliaceae family)

that is comprised of nearly 450 species and is found distributedwidely in the northern hemisphere (Lonzotti 2006). However,most of the plants belonging to the Allium genus are consumedregularly in many Asia-Pacific regions. The plants and their partsare used in cooking because of their characteristic flavor, attributeddue to sulfur-based compounds (Tada and others 1988). Evaluationof antimicrobial activity has been reported to support the thera-peutic value of these species as anti-infective agents (Chehreganiand others 2007).

The effective antimicrobial activities (of the aqueous extracts)of different parts of Allium spp. (bulbs, leaves, flowers, rhizomes)against pathogenic bacteria such as Shigella flexinix, Klebsiella pneu-moniae, Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, and Es-cherichia coli have been reported based on agar disc diffusion andserial dilution methods (Chehregani and others 2007). The re-ported diameter of inhibition zones for Allium atroviolaceum, Alliumeriophyllum, Allium scabriscapum, Allium stamineum, Allium iranicum,and Allium shelkovnikovii ranged from 8.5 to 36.2 mm, 6.4 to36.8 mm, 5.4 to 25.3 mm, 4.4 to 39.7 mm, 3.9 to 28.3 mm,and 0.0 to 27.8 mm. Moreover, the flower extracts of some Al-lium spp. (A. scabriscapum, A. iranicum, A. shelkovnokovii) exhibitedmuch higher antibacterial activity than the bulb extracts with MICvalues (ranging from 0.625 to 5.00 mg/mL, 2.50 to 12.50 mg/mL,and 2.5 to 10.00 mg/mL), indicating that the tannin accumulatedin the flowers to have played a role in exhibiting the antimicrobialactivities. While the bulbs of Allium spp. are known for their highantibacterial activities, the results of this study indicated that thefloral extracts from Allium spp. also have high potential for use asantibacterial agents.

Alpinia galanga (Linn.) Swartz. (greater galangal)Alpinia galangal (family: Zingiberaceae) is a stemless perennial

herb indigenous to South-East Asia and Indonesia. The plant bearslarge white flowers with a pleasant fragrance (Yang and Eilerman1999). Galangal plant parts have been traditionally used in Chinaand Thailand to relieve gastrointestinal pain and to treat mal-adies involving fungi (Yang and Eilerman 1999; Oonmetta-areeand others 2006). The flowers are either consumed raw or madeinto pickles in Asian cuisine (Yang and Eilerman 1999; Raina andothers 2002; Tonwitowat 2008). The plant’s rhizome is extensivelyused in Thai cooking for its unique ginger-like flavor accompaniedwith a tinge of pungent and peppery odor (Juntachote and others2007). Furthermore, this plant’s rhizome is also used for medicinalpurposes, which is reported to exhibit antifungal, antigardial, an-tiamebic, antimicrobial, and antioxidant activities (Juntachote andBerghofer 2005;Phongpaichit and others 2005; Oonmetta-areeand others 2006; Voravuthikunchai and others 2006; Juntachoteand others 2007; Hsu and others 2010).

36 Comprehensive Reviews in Food Science and Food Safety � Vol. 11, 2012 c© 2011 Institute of Food Technologists


Tabl

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Tabl

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d.

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dof

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ntia

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nSo

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Act

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ive

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them

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orifo

lium

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at(C

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)Sh

akin

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wat

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that

room

tem

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ture

for

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80%

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teria

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ivity

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enes

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oli,

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and

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rs(2

007)

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lete

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(3×)

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her,

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lac

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dm

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nol

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ntib

acte

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ityPe

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us,M

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ater

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atio

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ilis,

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cium

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gan

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hers

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ssed

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tle)

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erat

ion

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in8

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%et

hano

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ibac

teria

lact

ivity

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phim

uriu

m,S

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erit

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us,E

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pyog

enes

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aeru

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sa,B

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teus

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onne

i

Szab

oan

dot

hers

(200

9)

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cus

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vus

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ffro

n)M

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atio

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r3d

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eran

dm

etha

nol

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ntib

acte

riala

ctiv

ityH

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ori

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haei

and

othe

rs(2

008)

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erat

ion

for4

8h

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lace

tate

,eth

anol

,and

petr

oleu

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her

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ntib

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ider

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is,E

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i,M

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lado

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ium

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iger

Etha

nol:

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Petr

oleu

met

her:

Cla

dosp

oriu

msp

p.

Vah

idia

ndot

hers

(200

2)

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tala

ria

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eaL.

(Sun

nhe

mp)

Soxh

lete

xtra

ctio

nfo

r36

hEt

hano

l–

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ibac

teria

lact

ivity

E.co

li,K.

pneu

mon

iae,

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rugi

nosa

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ureu

s,V

.cho

lare

Chou

han

and

Sing

h(2

010)

Den

drob

ium

nobi

le(D

endr

obiu

m)

Extr

actio

nin

ash

aker

for

48h

Etha

nol,

chlo

rofo

rm,a

nddi

still

edw

ater

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ntib

acte

riala

ctiv

ityE.

coli,

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btili

s,Pr

oteu

s,S.

typh

i,an

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aure

usU

ma

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iand

othe

rs(2

009)

Etlin

gera

elat

ior(

Torc

hgi

nger

)So

lven

text

ract

ion

for1

wk

80%

met

hano

l–

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ibac

teria

land

antif

unga

lact

ivity

S.au

reus

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huri

ngie

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oli,

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onel

lasp

p.,P

.mir

abili

s,M

icro

cocc

ussp

p.,B

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tilis

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albi

cans

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iger

.

Lach

umy

and

othe

rs(2

010)

Euge

nia

cary

ophy

llata

Thun

b.or

Syzy

gium

arom

atic

um(C

love

)

Solv

ente

xtra

ctio

nfo

r48

h95

%et

hano

l–

Ant

ibac

teria

lact

ivity

E.co

liO

157:

H7,

Y.e

nter

ocol

itic

aSt

onsa

uvap

akan

dot

hers

(200

0)

Shak

ing

inw

ater

bath

atro

omte

mpe

ratu

refo

r24

h

80%

met

hano

l–

Ant

ibac

teria

lact

ivity

B.ce

reus

,L.m

onoc

ytog

enes

,S.

aure

us,E

.col

i,S.

anat

umSh

anan

dot

hers

(200

7)

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rodi

still

atio

nw

itha

Clev

enge

rapp

arat

usfo

r5h

––

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ifung

alac

tivity

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iger

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umig

atus

Bans

odan

dRa

i(2

008)

Solv

ente

xtra

ctio

n70

%m

etha

nol

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acte

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ctiv

ityS.

Typh

imur

ium

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ureu

s,En

tero

cocc

ussp

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iU

shim

aru

and

othe

rs(2

007)

cont

inue

d



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e1–

Cont

inue

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Plan

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etho

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ajor

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Met

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ibac

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ivity

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li,K.

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irab

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han

dot

hers

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0)

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re

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hano

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008)

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rodi

still

atio

nw

itha

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enge

rapp

arat

usfo

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ente

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ater

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011)

Men

tha

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sem

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n

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Has

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009)

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rodi

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atio

nw

itha

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enge

rapp

arat

usfo

r3to

4h

––

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ibac

teria

lact

ivity

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reus

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ubti

lis,P

.aer

ugin

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phi

Zahi

dan

dot

hers

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0)

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spp.

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wer

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xhle

text

ract

ion

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oleu

met

her,

alco

hol,

and

wat

er–

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ibac

teria

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ivity

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li,S.

pneu

mon

iae,

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phim

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m,E

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sa

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awal

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tex

trac

tion

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ane,

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nol

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ntib

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dot

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dock

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her,

ethe

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form

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det

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l

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ntib

acte

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ityK.

pneu

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iae,

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eum

onia

e,S.

pyog

enes

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ureu

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coli,

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rugi

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tafa

and

othe

rs(2

011)

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olin

aro

smar

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dist

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ion

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am

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ger

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––

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ans

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007)

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atio

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itha

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ente

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n

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arix

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isk)

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netic

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acte

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ityS.

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idis

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ake,

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9)

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ion:

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aure

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othe

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rs(2

004)



Therapeutic values (used in treatment of gastrointestinal pain, dysentery, gout, fever, muscle aches, skin diseases, liver disorder, etc.)

Solvent extracts (Aqueous, methanol, ethanol,

chloroform, hexane, etc.)

Essential oils (Obtained by hydro-distillation)

Tannins, flavonoids, saponins, triterpenoids, steroids, glycosides, anthraquinones, etc.

Pinene, limonene, spathulenol, myrcene,

terpinene, longifolene, cadinol, etc.

Spoilage microorganisms

(A. niger, B. subtilis, C. kefyr, C. holmii, E. aerogenes, E. faecalis, H. alvei, P. aeruginosa, S. marcescens, S. cerevisiae, Z. rouxii, etc.)

Pathogenic microorganisms

(C. albicans, E. coli O157:H7, L. monocytogenes,

S. aureus, S. Typhimurium, S. enteritidis,

S. epidermidis, T. mentagrophytes, T. simii, T.

rubrum, Scopulariopsis spp., etc.)

- Antimicrobial agents - Preservatives - Development of antimicrobial

packaging (biopolymer based edible films) for food applications

Pharmaceutical values (exhibit analgesic, anti-inflammatory, antioxidant,

anticancer, antitumor, anti-hyperglycemic, astringent activities, etc.)

Antimicrobial activities

Edible flowers

Figure 1–Schematic representation of edible flowers, their antimicrobial activities, and applications as natural antimicrobial agents.

By employing the agar disc diffusion method, antimicrobialactivity of galangal flower buds against both Gram-positive andGram-negative bacteria have been tested. The effects of dryingmethods (oven drying and freeze-drying) and solvents (hexaneand ethanol) on the antimicrobial activity have also been investi-gated (Hsu and others 2010). Galangal was shown to be effectiveagainst Gram-positive bacteria (Listeria monocytogenes and S. aureus)

but exhibited little or no effect against Gram-negative bacteria(Salmonella spp., E. coli O157: H7, and Shigella spp.). Overall,antimicrobial activity of galangal was the highest for oven-driedsamples extracted with ethanol (inhibition zone = 8.94 mm andMIC = 1.457 mg/mL) and the lowest for the freeze-dried sam-ples extracted with ethanol (inhibition zone = 7.05 mm and MIC= 2.470 mg/mL). Due to its ability to inhibit the growth of



Figure 2–Examples of some flowers with known antimicrobial activities belonging to the species of: a = Clitoria ternatea; b = Cassia fistula; c =Dendrobium nobile; d = Hibiscus spp.; e = Nelumbo spp.; f = Chrysanthemum spp.

Gram-positive bacteria, galangal flower buds have potential to beused as natural antimicrobial agent for preservation of perishablefoodstuffs.

Anthemis cotula L. (Stinking chamomile)Anthemis cotula (family: Asteraceae), a native of Europe and a

weed that grows extensively in Argentina, is commonly knownas Manzanilla del campo. Traditionally, A. cotula is believedto be effective for treatment of dysentery and gout. The de-coctions made from the leaves and flowers are reported toexhibit insecticidal properties (Quarenghi and others 2000).The flavonoid constituents present in this flower have beenreported to contain: quercetagetin, quercetagetin 7-glucoside,quercetin, quercetin 7-glucoside, patuletin, patuletin 7-glucoside,kaempferol, kaempferol 7-glucoside, and kaempferol 3-rutinoside(Quarenghi and others 2000).

Quarenghi and others (2000) employed the agar disc diffu-sion method to evaluate the antimicrobial activity of A. cotula(methanol extract) against some of the pathogenic microbes, suchas S. aureus, Staphylococcus epidermidis, Micrococcus luteus, Streptococ-cus pneumoniae, E. coli, Pseudomonas aeruginosa, Proteus vulgaris, andSalmonella spp. Owing to the flavonoid compounds present in theflower, methanol extract at a concentration of 200 μg/mL wasfound to exhibit rich antimicrobial activities against the bacteriatested (except for S. pneumoniae and Salmonella spp.) with diametersof inhibition zones ranging from 6.0 to 9.0 mm.

Bombax buonopozense P. Beauv. (Gold Coast Bombax)Bombax buonopozense (family: Bombaceae) is a large tropical tree

in Africa (found in Ghana, Uganda, and Gabon). The plant growsup to 40-m high with large buttress roots, which are spread upto6 m (Beentje and Sara 2001). This tree is also popular as “Vabga”in Ghana and “Kurya” in Northern Nigeria. The plant parts are

used as food, as building materials, for extracting dye, and also as asource of clothing fiber. The decoctions prepared from leaves androots are traditionally used to treat fever, muscle aches, pains, andstomach discomforts (Akuodor and others 2011).

Mann and others (2011) have evaluated antimicrobial activitiesof Bombax flowers against S. aureus, E. coli, and A. niger usingthe disc diffusion method. The results obtained clearly demon-strated antimicrobial activity of methanol, chloroform, hexane,and aqueous extracts against the 3 pathogens tested. However, thechloroform extract did not exhibit any activity against S. aureusand the aqueous extract showed no activity against A. niger. Theresults of this study were able to provide scientific evidence to sup-port the traditional uses of B. buonopozense for curing microbialinfections.

Cassia fistula Linn. (golden shower tree)Cassia fistula (family: Leguminosae) is an ornamental tree found

in various parts of China, India, Mauritius, South Africa, Mexico,the West Indies, East Africa, and Brazil. Various parts of this plantare used in the treatment of intestinal disorders, skin diseases,such as leucoderma, liver problems, tuberculosis, hemetemesis, di-abetes, rheumatism, hypercholesterolemia, and diarrhea. The fruitpulp is used as a laxative, purgative, antipyretic, analgesic, and an-timicrobial agent in Indian Ayurvedic medicine. Its flowers havebeen reported to exhibit antifungal activities (to treat skin infec-tion) and are used to treat nasal infections in certain tribal sects(Perumal Samy and others 1998; Prashanth Kumar and others2006; Duraipandiyan and Ignacimuthu 2007; Bhalodia and others2011). Also, flowers have been reported to be useful in treatingpruritus, burning sensation, dry cough, and bronchitis attributedto its demulcent, lubricating, cooling, and emollient effects(El-Saadany and others 1991; Duraipandiyan and Ignacimuthu2007; Bhalodia and others 2011).



Duraipandiyan and Ignacimuthu (2007) have reported antimi-crobial activity of hexane, chloroform, ethyl acetate, methanol,and water extracts (at 1.25, 2.5, and 5 mg/disc) of C. fistula floweragainst Gram-positive bacteria (S. aureus, S. epidermidis, B. subtilis,Enterococcus faecalis) and 1 Gram-negative bacterium (P. aeruginosa)with the inhibition zones ranging from 7 to 23 mm. The MIC forthe sensitive microorganisms (S. aureus, S. epidermidis, B. subtilis,E. faecalis, P. aeruginosa) were found to be 0.039 to 2.5 mg/mL.The compound 4-Hydroxy benzoic acid hydrate, which was ob-tained from ethyl acetate extract, showed a MIC of 0.5 mg/mLfor fungi, such as Trichophyton mentagrophytes and Epidermophytonfloccosum. The compound rhein (1, 8-dihydroxyanthraquinone-3-carboxylic acid) isolated from the ethyl acetate extract was foundto be effective against fungal pathogens, such as T. mentagrophytes,Trichophyton simii, Trichophyton rubrum, Epidermophyton floccosum,and a Scopulariopsis spp. with MIC values of 31.25, 125.00,62.50, 31.25, and 250.00 μg/mL, respectively (Duraipandiyan andIgnacimuthu 2010).

Sangetha and others (2008) evaluated the antimicrobial ac-tivity of methanol extracts from different parts (leaves, flowers,stems, and pods) of C. fistula and Cassia surattensis against 12 bac-teria and 3 fungi by using the agar disc diffusion assay. All thebacteria and fungi studied (except E. coli and Saccharomyces cere-visiae) were susceptible to the extract of C. fistula flowers withinhibition zones ranging from 12 to 20 mm.

Bhalodia and others (2011), in one of their studies, by em-ploying the agar disc diffusion method, screened the antimicrobialactivities of hydro-alcohol and chloroform extracts of C. fistula (5,25, 50, 100, and 250 ıg/mL) against S. aureus, Streptococcus pyo-genes, E. coli, P. aeruginosa, A. niger, Aspergillus clavatus, and Candidaalbicans. Results showed both the extracts to exhibit moderate tostrong antibacterial and antifungal activities (inhibition zones of 12to 21 mm for bacteria and 13 to 22 mm for fungi) at all the testedconcentrations, except for 5 μg/mL. Preliminary phytochemicalscreening performed in this study showed that the chemical com-pounds of the hydro-alcohol extract contained tannins, flavonoids,saponins, triterpenoids, steroids, glycosides, anthraquinones, re-ducing sugars, and amino acids, while those of the chloroformextracts were found to contain high amount of glycosides, pheno-lic compounds, tannins, and anthraquinones.

Cassia surattensis Burm.f. (Sunshine tree)Cassia surattensis (family: Leguminosae) is a flowering plant

native to South Asia, and found growing abundantly in India,Myanmar, Southern Pakistan, and Sri Lanka. The plants are grownas ornamental trees in tropical and subtropical regions. The barkand leaves of C. surattensis are believed to exhibit antiblenorrhagicproperties (Sangetha and others 2008).

In one of the experiments conducted by Sangetha and others(2008) on different parts (leaves, flowers, stems, and pods) of C.fistula and C. surattensis, all the bacteria and fungi studied (ex-cept Bacillus thuringiensis and S. cerevisiae) were susceptible to themethanol extract of C. surattensis flowers with inhibition zonesranging from 12 to 20 mm.

Chaerophyllum macropodum Boiss. (Chervil)Chaerophyllum macropodum (family: Apiaceae) is a biennial shrub

with hard pinnate leaves. In Iran and Turkey, the edible vegetableobtained from this plant is used as food and in the preparationof cheese (Durmaz and others 2006; Coruh and others 2007;Ebrahimabadi and others 2010). The organic solvent extract fromthe aerial parts of C. macropodum have been reported to exhibit

antibacterial activity against Gram-positive bacteria (Durmaz andothers 2006).

The antimicrobial activity of essential oil and methanolic ex-tracts from the flower of C. macropodum against 9 bacteria and 2fungi was determined by Ebrahimabadi and others (2010) whoemployed agar disc diffusion and mico-well dilution assays. Fromgas chromatography (GC) and gas chromatography-mass spec-trometry (GC-MS) analysis, the chemical composition of essentialoil was found to be comprised of 49 components representing98.3% to 99.4% of the oil with trans-β-farnesene (27.5%), trans-β-ocimene (20.9%), β-pinene (2.8%), limonene (12.0%), spathu-lenol (8.6%), and myrcene (1.3%) as the major constituents. Theessential oil was found to be active against all the tested microor-ganisms (except for Shigella dysenteriae and A. niger) with inhibitionzones recorded as 8 to 26 mm and MIC recorded to be 125 to500 μg/mL. However, the methanol extract did not show anyinhibitory effects on the tested microorganisms.

Chrysanthemum morifolium Ramat. (Chrysanthemum)Chrysanthemum morifolium (family: Asteraceae) is an important

medicinal herb of the Asteraceae family consisting of 8 majorvarieties (Hangju, Boju, Gongju, Chuju, Qiju, Huaiju, Jiju, andHang ju). C. morifolium is traditionally used in China to protectthe cardiovascular system, to lower blood glucose and fat levels,to regulate blood pressure, excrete lead, and to scavenge free rad-icals. This plant has been reported to exhibit significant antibac-terial, antioxidant, anti-inflammatory, and anticancer activities.The bioactive compounds of C. morifolium consist of flavonoids,sesquiterpenoids, chlorogenic acids, vitamins, and amino acids(Zhang and Zhang 2007; Zhao and others 2009).

The methanolic extract of C. morifolium (inflorescence) showedantimicrobial activity against B. cereus, L. monocytogenes, E. coli, andSalmonella anatum with inhibition zones in the range of 5.5 to9.2 mm (Shan and others 2007). Besides, the antimicrobial activ-ity of petroleum ether, ethyl acetate, and methanolic extracts of 7species of C. morifolium flowers cultivated in Kaifeng, China weretested against S. aureus and methicillin resistant S. aureus (MRSA)by the disc diffusion assay (Zhao and others 2009). Petroleumether extracts of Mailang, Chunrijianshan, and Lengyan, as wellas ethyl acetate extracts of Mailang, Chunrijianshan, Lengyan,Jianliuxiangbai, Guohuawansheng, and Changhong varietiesshowed good antibacterial activity on S. aureus with MIC of 125,250, 250, 250, 250, 125, 250, and 250 μg/disc, respectively. Thepetroleum ether extracts of Mailang, Chunrijianshan, and Lengyanwere active against MRSA with MIC of 250 μg/disc. All the ex-tracts of Baiyudai did not exhibit any activity against S. aureusand MRSA at the tested concentration (250 μg/disc). Also, themethanol extracts of all the species of C. morifolium did not showany antimicrobial activity. The authors have concluded that betterantimicrobial activity was shown by yellow flowers compared topurple and white flowers.

Chrysanthemum trifurcatum (Desf.) Batt. and Trab.Chrysanthemum trifurcatum (family: Asteraceae) is an herbal plant

bearing small yellow flowers. This plant is widely distributed inTunisia regions and the plant parts are used for treating constipa-tion, intestinal transit problems, and postdelivery pains (Sassi andothers 2008b). The antimicrobial activity of petroleum ether, ethylacetate, methanol, and hot water extracts of Tunisian Chrysanthe-mum species against 5 Gram-positive and 9 Gram-negative bac-teria and 4 yeasts were evaluated by Sassi and others (2008a)by employing agar disc diffusion and microdilution assays. The



results obtained showed all the extracts to inhibit growth of thetested microorganisms (inhibition zone = 7.1 to 8.5 mm; MIC =1.25 mg/mL) except for S. aureus, E. coli, K. pneumoniae, Aeromonashydrophila, C. albicans, and Candida tropicalis.

Further, the same authors have reported on the antimicro-bial activity of the essential oil from C. trifurcatum flower headsagainst 5 Gram-positive bacteria (S. epidermidis, Staphylococcus hoe-molyticus, Staphylococcus hominis, Staphylococcus simulans, and B. sub-tilis) and 3 Gram-negative bacteria (E. coli, Hafnia alvei, andProteus mirabilis) (Sassi and others 2008b). The broth microdi-lution method was adopted for assaying antimicrobial activities.The essential oil was found to exhibit better antimicrobial ac-tivity against Gram-negative bacteria compared to Gram-positivebacteria. At a concentration of 500 μg/mL, the essential oil in-hibited the growth of S. epidermidis and B. subtilis by 66% and 64%with IC50 (concentration that inhibits 50% of growth) of 62.5and 125 μg/mL, respectively. The authors reported the presenceof 56 compounds representing 97.48% of the oil with limonene(20.89%), γ -terpinene (19.13%), 1,8-cineole (10.64%), β-pinene(8.77%), α-pinene (5.32%), 2-hexenal (4.85%), 4-terpenyl ac-etate (3.42%), β-myrcene (2.31%), germacrene-B (2.01%),β-spathulenol (1.62%), longifolene (1.39%), α-cadinol (1.39%),α-thujene (1.23%), and β-bourbobene (1.06%) as the major con-stituents that contributed to the antibacterial activity of the essen-tial oil.

Cleistocalyx operculatus (Roxb.) Merr and Perry (water fairyflower)

Cleistocalyx operculatus (family: Myrtaceae), also known as Eu-genia operculata or Syzygium nervosum, is a perennial tree, widelydistributed in China, Vietnam, and other tropical countries. Tra-ditionally, the leaves and flower buds of the plant have been re-ported to be used as an ingredient in preparing certain beverages(tea decoctions) for treating gastrointestinal disorders and antisepsis(Dung and others 2008). In vivo and in vitro studies have shown thepotentiality of C. operculatus buds to exhibit anticancer, antitumor,antihyperglycemic, and cardiotonic properties (Anthony and oth-ers 2002; Ye and others 2005; Mai and Chuyen 2007; Dung andothers 2008). Results on the phytochemicals screening of flowerbuds have shown the presence of sterols, flavanones, chalcones,triterpene acid, β- sitosterol, and ursolic acids in the buds (Ye andothers 2004; Dung and others 2008).

Dung and others (2008), by using agar disc diffusion and mi-crodilution susceptibility tests, have screened the effectiveness ofthe essential oil and ethanol extract of C. operculatus buds against2 food spoilage bacteria (B. subtilis and P. aeruginosa), 9 foodbornepathogens (2 isolates of S. aureus, L. monocytogenes, Enterobacter aero-genes, Salmonella Typhimurium, Salmonella enteritidis, E. coli, and 2isolates of E. coli O157:H7), 4 skin infectious pathogens (S. aureus,S. epidermidis, E. coli, and C. albicans), 3 methicillin-resistant S.aureus, 3 vancomycin-resistant Enterococcus faecium, and 15 multi-antibiotic-resistant bacteria (2 isolates of Acinetobacter baumannii,3 isolates of E. coli, 2 isolates of Enterobacter cloacae, 2 isolatesof K. pneumoniae, 3 isolates of P. aeruginosa, 2 isolates of Serratiamarcescens, and S. aureus). The essential oil of C. operculatus budsshowed inhibition zones and MIC/MBC, which ranged from 8to 16 mm and 1 to 20 μL/ mL, respectively, effective against allthe tested microorganisms. The ethanol extract demonstrated an-timicrobial activity against all the Gram-positive bacteria and 1food-spoilage Gram-negative bacterium (P. aeruginosa) with inhi-bition zones and MIC/MBC in the range of 8 to 22 mm and 0.25to 32 mg/mL. Besides, in the cell viability assay of methicillin-

resistant S. aureus (MRSA) and vancomycin-resistant Enterococci(VRE), the authors found essential oil at the MBC (8 and 16μL/mL) to possess potential inhibitory effects with the exposuretime required for complete inhibition of cell viability to rangefrom 10 to 40 min and 10 to 20 min, respectively. Scanningelectron spectroscopy on the most sensitive methicillin-resistantS. aureus and vancomycin-resistant Enterococcus (MRSA–P249 andVRE–B2332) treated with essential oil at MIC (8 μL/mL) showeddisruption and lysis of membrane integrity. The essential oilwas found to contain 55 compounds representing 93.71% ofthe oil with γ -terpinene (5.76%), cis-linalool oxide (5.21%),camphene (4.12%), trans-carveol (3.93%), α-pinene (3.45%), β-pinene (3.07%), terpinen-4-ol (2.58%), and myrcene (2.4%) as themajor monoterpenes as well as globulol (5.61%), acorenol (5.12%),β-himachalol (3.84%), cyclobazzanene (3.12%), 2,3-dehydro-1,4-cieol (3.01%), trans-dihydrocarvone (2.58%), presilphiperfol-1-ene (2.48%), and γ -amorphene (2.12%) as the major sesquiter-penes. The authors, for the first time, concluded the use of essentialoil and ethanolic extract of C. operculatus to have applicability forthe prevention and treatment of diseases caused by foodborne andskin-infectious pathogens, especially those of antibiotic-resistantstrains.

Clitoria ternatea Linn. (butterfly pea, Asian pigeon wings)Clitoria ternatea (Family-Liguminoceae) is a tropical, perennial

twining herb bearing blue or white colored flowers (in single).This plant is extensively grown for ornamental and medicinalpurpose in the Asian subcontinent (India, Bangladesh, Indonesia,Malaysia). In Malaysia, aqueous extract of the flower is used asa natural coloring agent for preparing dish from glutinous rice.The plant parts have been reported to exhibit anti-inflammatory,antipyretic, antihyperlipidemic, analgesic, tranquilizing, and im-munomodulatory activities (Mukherjee and others 2008; Solankiand Jain 2010, 2011, 2012). Root contains flavonol glycosides,which exhibit rich antibacterial activity (Yadava and Verma2003).Cliotides (biologically active peptides) (present in flowers, seeds,and nodules) have been isolated from heat-stable fractions of Clito-ria ternatea extract. These cliotides showed potential antimicrobialactivity against E. coli and cytotoxicity against HeLa cells (Nguyenand others 2011).

Uma and others (2009) have screened the flower extracts(by maceration technique: solvents used methanol, chloro-form, petroleum ether, hexane, and aqueous) of Clitorea ter-natea against pathogenic microorganisms, such as uropathogenic,enteropathogenic, and enterotoxigenic E. coli, S. Typhimurium,S. enteritidis, K. pneumoniae, and Pseudomonas aureginosa. Thesemicroorganisms were isolated from patients with urinary tractinfection and acute gastroenteritis. The method adopted fordetermining antimicrobial activity was disc diffusion methodand minimum inhibitory concentration (two-fold serial dilu-tion method). Results of this study revealed aqueous, methanol,and chloroform extracts to exhibit antimicrobial activity againsturopathogenic, enteropathogenic, and enterotoxigenic E. coli, S.Typhimurium, K. pneumoniae, and P. aureginosa. However, no an-tibacterial activity was recorded for petroleum ether and hexaneextracts.

Cnicus benedictus Linn. (blessed thistle)Cnicus benedictus (family: Asteraceae) is the single species in the

genus Cnicus; it is native to the Mediterranean region. This annualplant grows up to 60-cm high, and has leathery, hairy leaves (ex-tending up to 30-cm long and 8-cm broad), with minute spines



on the leaf margins. The flowers are yellow, which are producedin a dense flower head of 3 to 4 cm dia. The entire plant of C.benedictus possesses astringent, bitter, diaphoretic, diuretic, emetic,emmenagogue, galactogogue, stimulant, stomachic, and contra-ceptive properties. An aqueous infusion of the entire plant isreported to be used for the treatment of liver and gall bladderproblems. The flowers, leaves, and stem of C. benedictus are tra-ditionally used as a health drink (tonic) or used in other prepa-rations taken orally to improve appetite and digestion (extractsare believed to stimulate gastric juices). This plant is known tocontain ample amounts of sesquiterpene lactones, alkaloids, tan-nins, and volatile oil. Besides this, anti-infective, anticancer, andanti-inflammatory activities of C. benedictus have been reportedthrough laboratory studies by Szabo and others (2009). In addition,the chemical constituents (such as cnicin and polyacetylene) havebeen reported to exhibit antibacterial activity (Szabo and others2009).

The effects of ethanol extracts of C. benedictus flowers againstAmerican Type Culture Collection (ATCC) bacterial strains (S.Typhimurium, S. enteritidis, S. aureus, E. coli, S. pyogenes, P. aerug-inosa, Bacillus proteus, and Shigella sonnei) and pathogens obtainedfrom hospitalized patients (S. aureus, S. pyogenes, and E. coli) wereassessed by using the agar disc diffusion assay (Szabo and oth-ers 2009). The antimicrobial activity of the C. benedictus flowersagainst all the tested bacteria were observed with inhibition zonesof approximately the same values at different concentrations ofthe extracts (10% and 20%, respectively). The diameters of inhi-bition zones shown by C. benedictus mature flowers (16 to 30 mm)on ATCC bacterial strains were significantly different from thoseshown by immature flowers (18 to 32 mm). The test results on themicroorganisms harvested from hospitalized patients treated withthe extract of mature flowers showed diameters of inhibition zonesto range between 10 and 24 mm.

Crocus sativus Linn. (saffron)Crocus sativus (family: Iridaceae) has been used traditionally as

a spice and as a food colorant in most of the countries over theworld. Saffron, the world’s most expensive spice is obtained fromthe flower (mainly the stigmata) of the C. sativus plant. In folkmedicine, saffron has been used as aphrodisiac, antispasmodic, andexpectorant (Nakhaei and others 2008). Saffron is also used to treatflatulence, colic, and abdominal pains, as well as to improve ap-petite and memory (Zhang and others 1994; Nakhaei and others2008). Antitumor, radical scavenging, hyperlipemic, anticonvul-sant, cytotoxic, antigenotoxic, and anti-ulcerogenic activities havebeen reported for C. sativus extracts or their chemical constituents(Nair and others 1995; Hosseinzadeh and Khosravan 2001;Abdullaev and others 2003; Al- mofleh and others 2006; Nakhaeiand others 2008). The biological properties of C. sativus are mainlyattributed to crocin and saffranal, which are isolated from stigmata,leaves, petal, and pollen. Other isolated chemical constituents in-clude crocetin, picrotoxin, quercetin, and kaempferol (Nakhaeiand others 2008).

According to Vahidi and others (2002), significant antimicrobialactivity was observed against S. epidermidis, C. albicans, Cladosporiumspp., and A. niger when an ethyl acetate extract of stigmata of C.sativus was used. The inhibition zones and MIC ranged from 12to 19 mm and 6.25 to 50 mg/mL, respectively. The ethyl acetateextract of stamens exhibited antimicrobial activity against S. aureus,S. epidermidis, E. coli, M. luteus, Cladosporium spp., and A. niger withinhibition zones and MIC ranging from 15 to 21 mm and 12.5 to50 mg/mL, respectively.

Nakhaei and others (2008) screened the anti-Helicobacter pyloriactivity of stigmata of C. sativus against 45 clinical isolates. Basedon the results obtained from the agar disc diffusion method, theaqueous and methanol extracts of saffron exhibited antibacterialactivity against all the isolates with inhibition zones being in therange of 10 to 23.5 mm. Based on the agar dilution method, theMIC of the methanol extract for all the isolates was 677 μg/mL.There was no significant difference in the activity of methanolextract at 80 and 121 ◦C, in comparison to the control, indicatingthat high temperature not to have any effect on the activity of theextract. The results on pH stability of the methanol extract in thisstudy indicated that active compounds of C. sativus were stable atpH 5, 6, 7, and 8.

Crotalaria juncea Linn. (sunn hemp)Crotalaria juncea (family: Leguminoceae) plant parts (flowers,

buds, pods, and seeds) are commonly used as medicine and forculinary purposes (Bhatt and others 2009). The plant is widelydistributed in tropical and subtropical regions, such as in India,Nepal, Sri Lanka, and Southern Africa. In Ayurvedic medicine, C.juncea has been used as an astringent, abortifacient, blood purifier,demulcent, emetic, purgative, and for curing anemia, impetigo,menorrhagia, and psoriasis (Sharma and others 2001; Chouhanand Singh 2010). The seeds of C. juncea have been reported to ex-hibit significant antispermatogenic, anti-ovulatory, and contracep-tive activities (Vijaykumar and others 2004; Malashetty and Patil2007). The chemical compounds isolated from the seeds of thisplant were riddelline, seneciphylline, senecionine, trichodesmine,chodesmine alkaloids, galactose-specific lectin, and cardiogenin3-O-[�]-d-xylopyranoside (Adams and Gianturco 1956; Chouhanand Singh 2010).

Chouhan and Singh (2010) have reported antibacterial activityof the ethanolic extract of C. juncea flowers against both Gram-positive and Gram-negative bacteria by employing the agar discdiffusion assay. The extracts were found to be effective againstE. coli, K. pneumoniae, P. aeruginosa, S. aureus, and Vibrio cholare(inhibition zone = 13, 14, 10, 13, and 8 mm). However, theextracts did not exhibit any activity against Citrobacter freundi, E.faecalis, Shigella flexneri, and S. dysenteriae. Further, the authorshave reported on the presence of steroids, triterpenes, flavonoids,phenolics, and glycosides in the ethanol extract.

Dendrobium nobile Lindl. (dendrobium orchid)Dendrobium nobile (family: Orchidaceae) is a flowering orna-

mental plant encompassing nearly 35000 species. The flowersare very attractive and appear in various colors and forms. Theopened flowers mimic bees, wasps, butterflies, moths, frogs, lizards,and even humans. Native inhabitants of the Eastern Himalayas(in India) believed that dendrobium flowers can cure eye dis-eases (Uma Devi and others 2009). Gigantel and moscatilin of D.nobile have been reported to exhibit antimutagenic activity and its2-phenanthrenes to exhibit anticancer activity (Kong and others2003; Uma Devi and others 2009).

Uma Devi and others (2009) used the “strip plate method” toevaluate the antimicrobial activities of different solvent (methanol,chloroform, and water) extracts of flowers and stems of D. nobileagainst pathogenic bacteria, such as E. coli, B. subtilis, Proteus spp.,S. Typhimurium, and S. aureus. The extent of inhibition of floralextracts was high in the aqueous extract than in the other 2 extracts.The authors recorded the inhibition zones as 0.6 to 1.0 mm forethanol extract, 0.3 to 1.0 mm for chloroform extract, and 0.53to 1.2 mm for aqueous extract. Also, in aqueous extracts, the



inhibitory activity was found to be significantly higher in flowersthan that of stems.

Etlingera elatior (Jack) R.M. Smith (torch ginger)Etlingera elatior (family: Zingiberaceae) is a perennial herbal plant

(height of 3.6 to 4.7 m) found growing abundantly in parts ofMalaysia, Indonesia, Vietnam, Sri Lanka, and Thailand. The flower(bud or inflorescence) is used both ornamentally and as a spice forculinary use. Rhizome and flowers of this plant are extensivelyused as a natural ingredient in cosmetics (as an ingredient of soap,shampoo, perfume) and also as a therapeutic agent for treatingcommon ailments. Fruits of the torch ginger plant are traditionallyused to treat ear ache, while leaves find use to clean wounds andto remove body odor (Chan and others 2007). Flowers and themature inflorescence of torch ginger are used to prepare suchpopular dishes as asam laksa, nasi kerabu, nasi ulam (in Malaysia),arisk ikan mas (in North Sumatra, Indonesia), and sayur asam (inThailand) (Lachumy and others 2010; Wijekoon and others 2011).Torch ginger inflorescence is reported to possess strong antioxidantactivities (Wijekoon and others 2011).

Lachumy and others (2010) evaluated the antimicrobial activity(by agar disc diffusion and serial dilution methods) of an 80%methanolic extract of torch ginger flowers against 7 strains ofbacteria, 1 strain of yeast, and 1 strain of mold. Results of this studyshowed methanol extract of the flowers to possess high amounts offlavonoids, terpenoids, saponins, tannins, and carbohydrates. Floralextracts were found to be active against the tested microorganisms(inhibition zone = 12 to 23 mm; MIC = 1.563 to 50.000 mg/mL).Results from the brine shrimp lethality test revealed absence oftoxicity of the flower extract (LC50 = 2.52 mg/mL against Artemiasalina), and therefore are nontoxic to humans.

Eugenia caryophyllata Thunb. (synonym, Syzygium aro-maticum) (clove)

Eugenia caryophyllata (family: Myrtaceae) is commonly foundgrowing in warm and humid climatic conditions, such asthose encountered in tropical Asia (India, Sri Lanka, Malaysia,Indonesia). The handpicked, unopened, air- or sun-dried flowerbuds are used as spice. Traditionally, the floral buds have been usedto treat tooth aches. The essential oil obtained from buds are ex-tensively used as an ingredient of dental formulations, toothpastes,breath fresheners, mouthwashes, cosmetics, soaps, and insect re-pellents (Politeo and others 2010). The essential oils have beenreported to exhibit good antibacterial, antifungal, cytotoxic, andantioxidative activities (Baratta and others 1998; Gayoso and others2005; Prashar and others 2006).

Stonsaovapak and others (2000) have reported on the inhibitoryeffects of ethanolic extracts of E. caryophyllata flowers againstpathogenic E. coli O157:H7 and Yersinia enterocolitica with inhi-bition zones of 17.75 and 18.00 mm. At 3.0 × 104 CFU/mL,the MIC for E. coli O157: H7 was 1250 μg/mL, while at 3.0 ×106 CFU/mL, the MIC was 2500 μg/mL. For Y. enterocolitica, theMIC was 625 μg/ mL at 6.0 × 104 CFU/mL and 1250 μg/mLat 6.0 × 106 CFU/ mL.

Shan and others (2007) have reported effectiveness of methanolextracts of E. caryophyllata against B. cereus, L. monocytogenes, S.aureus, E. coli, and S. anatum with inhibition zones being in therange of 10.1 to 21.3 mm. And Ushimaru and others (2007) havereported methanol extract of E. caryophyllata to effectively inhibitthe growth of S. Typhimurium, S. aureus, Enterococcus spp. and E.coli (MIC 50% = 0.41% to 1.60% v/v and 0.39 to 1.52 mg/mL;MIC 90% = 0.49% to 1.76% v/v and 0.46 to 1.67 mg/mL).

Bansod and Rai (2008), reporting on the antifungal (againstAspergillus fumigatus and A. niger) assays of some Indian medicinalplants isolated from patients with pulmonary tuberculosis notedE. caryophyllata to exhibit antifungal activity. Based on the discdiffusion assay, the essential oil of E. caryophyllata was found toexhibit moderate antifungal activity with inhibition zones rangingfrom 8 to 15 mm. The MIC, determined by the agar dilutionmethod, was found to be 0.12% (v/v) for both of the fungi,while the MIC/MLC (determined by the broth microdilutionmethod) was found to be 0.06%/0.12% (v/v) for A. fumigatus and0.12%/0.06% (v/v) for A. niger, respectively. The authors haveconcluded that the essential oil of E. caryophyllata might play apivotal role in treating mycotic infections.

Euphorbia hirta Linn. (asthma weed)Euphorbia hirta (familiy: Euphorbiaceae) is a small perennial herb

that is found widely spread in tropical regions of the world. Theplant is erect, bears a slender hairy stem, and grows up to 80 cmin height. Occasionally, the plant is also witnessed to grow as asemicreeper. The leaves are broad, elliptical, oblong, and lanceo-late, darker on the upper surface with slightly toothed margins.Flowers of this plant are small, numerous, and crowded togetherin dense cymes (about 1 cm in diameter).

The stems and leaves contain milky-white latex. Rajeh and oth-ers (2010) have reported on the traditional use of E. hirta plantdecoctions to treat amebic dysentery, diarrhea, peptic ulcers, heart-burn, vomiting, respiratory problems (bronchitis, coughs, colds),kidney stones, and fertility-related problems (menstrual problems,sterility, and venereal disease). In certain instances, the plant partshave been recommended to be used as an antidote and to relievepain from scorpion stings or snake bites.

Methanolic extracts from different parts of E. hirta (leaves, flow-ers, stems, and roots) were evaluated by Rajeh and others (2010) forantimicrobial activities against 4 Gram-positive bacteria (S. aureus,a Micrococcus spp., B. subtilis, and B. thuringiensis), 4 Gram-negativebacteria (E. coli, K. pneumoniae, Salmonella typhi, and P. mirabilis)and 1 yeast species (C. albicans). Results of this study, which werebased on the agar disc diffusion method, revealed all the testedmicroorganisms, except C. albicans, to be sensitive to the flowerextract, with inhibition zones formed ranging from 9 to 28 mm.The LC50 value (0.033 mg/mL) against Artemia salina, which wasobtained from the brine shrimp lethality test, demonstrated thatE. hirta flower extract might be toxic to humans.

Helichrysum gymnocomum DC.Helichrysum gymnocomum (family: Asteraceae) is a perennial herb

with long flowering seasons commonly encountered in regions ofKwazulu-Natal Drakensburg, Africa. The pleasant scented flowersand leaves are burnt by the indigenous people of this region tofumigate sick rooms and to invoke the goodwill of ancestors. H.gymnocomum has also been traditionally used for the treatment ofwounds, coughs, and colds (Drewes and Van Vuuren 2008).

The antimicrobial activities of H. gymnocomum dichloromethane(CH2Cl2/MeOH) extract and isolated compounds against 5Gram-positive bacteria, 3 Gram-negative bacteria, and 2 yeastswere evaluated by Drewes and Van Vuuren (2008) by the serial di-lution method. From the results, it was noteworthy that the crudeextracts demonstrated antimicrobial activities with MIC rangingfrom 312.5 to 1000 μg/mL.

All the isolated compounds (2′-hydroxy-4′,6′-dibenzyloxy-chalcone; 5,7-dibenzyloxyflavanone; an acylphloroglucinolderivative; 1-[2,4,6-trihydroxy-3-(2-hydroxy-3-methyl-3-



butenyl)-phenyl]-1-propanone; 3-methoxyquercetin; a 4′-O-glucose derivative of 2′-hydroxy-6′-methoxy chalcone) weregood inhibitors against the tested microorganisms with MICvalues below 64 μg/mL. The findings of this study showedacylphloroglucinol derivative to be the most potent inhibitor for8 of the 10 tested microorganisms (MIC = 6.3 to 45 μg/mL),including S. aureus (MIC = 6.3 μg/mL) and methicillin-and gentamycin-resistant S. aureus (MIC = 7.8 μg/mL). Theresults also revealed highest sensitivity of P. aeruginosa to all thecompounds (except 5, 7-dibenzyloxyflavanone) with MIC beingin the range of 45 to 63 μg/mL. According to the authors, thetraditional use of H. gymnocomum in healing wound infectionswas supported by the notable antimicrobial activity of the plant,particularly against S. aureus and P. aeruginosa.

Hibiscus sabdariffa Linn. (roselle)Hibiscus sabdariffa (family: Malvaceae) is a small shrub native

to Africa and is cultivated in parts of Sudan and Eastern Tai-wan (Lin and others 2007). The plant parts are used in the treat-ment of hypertention, pyrexia, and liver disorders (Wang and oth-ers 2000; Odigie and others 2003). In vitro and in vivo studieshave demonstrated cardio-protective (Odigie and others 2003),hypo-cholesterolemic (Chen and others 2003), antioxidative, andhepatoprotective (Wang and others 2000; Liu and others 2002)properties of the anthocyanins and protocatechuic acid, whichwere isolated from dried flowers of H. sabdariffa.

The floral extract (water and ethanol) of H. sabdariffa has beenreported to show high inhibitory effects against B. cereus (Hamdanand others 2007). The inhibition zones against B. cereus were2, 6, and 16 mm and 4, 9, and 12 mm at 1, 2, and 4 mg/mL forwater and ethanol extracts, respectively. The authors also notedthat as the content of water and ethanol extract increased (from0.82 to 4.12 mg/mL), a corresponding increase in the inhibitionon the growth of B. cereus occurred with complete inhibition(100%) attained at a concentration of 3.45 and 4.12 mg/mL, re-spectively. Besides, heat treatment at 70 ◦C for 3 min did notsignificantly affect the antibacterial activity of H. sabdariffa extractagainst B. cereus.

Jasminum sambac (Arabian jasmine/jasmine flower)Jasminum sambac (family: Oleaceae) originated in India and

Burma and is widely grown in Ambouli (Republic of Djibouti)for producing perfume. This plant is a perennial twining shrub(attaining height of 5 to 6 feet) and bearing small, white-coloredscented flowers. The flowers are used ornamentally as well as todecorate hair. Skin care products are also formulated by using theessential oil extracted from the flowers. The essential oil of theflower is used to reduce skin inflammation, tone the skin, andlift up mood (Abdoul-Latif and others 2010). Extracts of flowersare also used to prepare herbal tea decoctions. The floral extractis reported to possess analgesic, anti-inflammatory, antidepressant,aphrodisiac, antiseptic, expectorant, sedative, and tonic properties.Besides, flowers and plant parts have been reported to have an-ticancer properties (Houghton and others 2007; Alka and others2010).

Tsai and others (2008) have reported on the inhibitory ac-tivities of methanolic extract of the flowers against Streptococcusmutans and Streptococcus sanguinis. They adopted the broth microdi-lution method for evaluating the antimicrobial/inhibitory activ-ities. From their study, they reported the MIC to be 1 mg/mLfor S. sanguinis. However, the MIC of the extract for S. mutanwas >8 mg/mL, which is an indication of “no activity” against S.mutans.

Lonicera japonica Thunb. (honeysuckle)Lonicera japonica (family: Caprifoliaceae) is a native plant of east-

ern Asia and is widely seen in parts of Japan, Korea, northernand eastern China, and Taiwan. Flower buds of this plant pos-sess anticancer, antimicrobial, and anti-inflammatory properties(Zhang and others 2008). Results on the phytochemical screeninghave reported the presence of iridoid glucosides and polyphenoliccompounds in the flower buds (Kakuda and others 2000).

Based on the results obtained by the agar well diffusion method,methanol extracts of the flower showed inhibitory activities againstB. cereus, S. aureus, and S. anatum with the diameters of inhibitionzones ranging from 5.5 to 7.2 mm (Shan and others 2007). Onanother note, Tsai and others (2008), screening on the methano-lic extract of different herbs against growth of S. mutan and S.sanguinis, found MIC of L. japonica to be 4 mg/mL for S. sangui-nis, while MIC for S. mutan was >8 mg/mL (no activity).

In another study reported by Rahman and Kang (2009), theessential oil of L. japonica flower demonstrated inhibitory activ-ities against L. monocytogenes, B. subtilis, B. cereus, S. aureus, S.enteritidis, S. Typhimurium, E. aerogenes, and E. coli with inhibitionzones recorded in the range of 12.1 to 20.3 mm and MIC inthe range of 62.5 to 500 μg/mL. The authors used the agardisc diffusion and broth dilution assays for the analysis. Theirresults of a GC-MS analysis showed the essential oil to con-tain 39 compounds wherein 92.34% of the oil was composed oftrans-nerolidol (16.31%), caryophyllene oxide (11.15%), linalool(8.61%), p-cymene (7.43%), hexadecanoic acid (6.39%), eugenol(6.13%), geraniol (5.01%), trans-linalool oxide (3.75%), globulol(2.34%), pentadecanoic acid (2.25%), veridiflorol (1.83%),>br/>benzyl alcohol (1.63%), and phenylethyl alcohol (1.25%) as majorcomponents. However, antimicrobial activity results on the essen-tial oil did not reveal any effects of the oil against E. coli O157: H7and P. aeruginosa.

Recently, Rhee and Lee (2011) reported the antimicrobial ac-tivity of butanol extract from L. japonica flower against 104 clinicalisolates of anaerobic bacteria (Bacteroides fragilis, Bacteroides ovatus,Clostridium difficile, C. perfringens, Propionibacterium acnes, and Pep-tostreptococci) (based on the agar dilution method). The butanolextract showed antimicrobial activity against all the tested bacteriawith MIC ranging from 0.032 to 2.0 mg/L.

Mentha longifolia L. (horse mint)Mentha longifolia (family: Lamiaceae) is a perennial herb

commonly found growing in a hot and humid climate. Mint iswidely distributed throughout South Africa, Botswana, Namibia,and Zimbabwe. The rhizomes creep below the ground andthe erect flowering stems can grow up to 8-m high. The plantbears small white or pale purple flowers borne in elongatedclusters on the tips of the stems. The entire plant exudes aunique mint aroma. The leaves are the most widely used partsof this plant. Leaf and stem decoctions are prescribed to curecommon colds, cough, bronchial ailments, headache, fever,indigestion, flatulence, painful menstruation, urinary tract infec-tions, diseases of the gastrointestinal tract, and bleeding problems(http://www.plantzafrica.com/medmonographs/menthlong.pdf,accessed on Jul 25, 2011).

In one of the experiments conducted by Pirbalouti and others(2010) on Iranian folklore herbs, the extract and essential oil fromflowers of M. longifolia have been reported to exhibit strong an-tibacterial activity against all the tested bacteria (S. aureus, E. coli,P. aeruginosa, and K. pneumoniae) with inhibition zones and MICvalues ranging from 9 to 17 mm and 0.156 to 10.00 mg/mL,



respectively. Results of this study showed the essential oil of M.longifolia to exhibit stronger antibacterial activity than the ethanolextract.

Moringa oleifera (horseradish tree)Moringa oleifera (family: Moringaceae) is a perennial timber

yielding softwood tree. It is native to the sub-Himalayan tractsof India, Pakistan, Bangladesh, and Afghanistan. The plant is alsofound to be widely distributed in parts of Ethiopia, the Philippines,Africa, Latin America, the Caribbean, Florida, and the PacificIslands (Fahey 2005). The whole plant is edible and possesses an-tispasmodic, anti-inflammatory, diuretic, obortifacient, emmena-gogue, and ecbolic properties. The plant parts have been reportedto possess therapeutic value and are used in the treatment of hys-teria, tumors, leucoderma, and biliousness (Fahey 2005; Talreja2010).

The potential antimicrobial activity of ethanolic extracts of itsflowers against B. subtilis, S. aureus, E. coli, K. pneumoniae, andC. albicans has been reported by Talreja (2010). Results basedon the agar disc diffusion assay showed the floral extract to haveboth antibacterial and antifungal activity with zones of inhibitionformed in the range of 8 to 10.5 mm for bacteria and 6.5 mm forC. albicans.

Lotus (Nymphaea lotus Linn., Egyptian white waterlily; andNelumbo nucifera L., Indian lotus, sacred lotus)

Nymphaea lotus (family: Nymphaeaceae) is an aquatic plant,widely seen in tropical Africa and in parts of Asia. It is a peren-nial herb growing about 10- to 60-cm high. The entire plant isreported to possesses therapeutic value and is used as an anticancerand antiviral agent and as an antioxidant (Saleem and others 2001;Esimone and others 2006; Sowemimo and others 2007a, 2007b).

The antimicrobial activity of hot water and ethanolic ex-tracts of 6 plants, utilized in Pakistan for the treatment of liverdamage, against 7 bacterial strains (methicillin-resistant S. aureus,multidrug-resistant P. aeruginosa, enterohemorrhagic E. coli 0157EHEC, S. typhi, P. vulgaris, K. pneumoniae, B. subtilis and 2 fungalspecies (C. albicans and A. niger), was determined by agar welldiffusion and broth microdilution assays (Hassan and others 2009).Both extracts of N. lotus were active against all the microorganismstested with zones of inhibition in the range of 16 to 36 mm andMIC/MBC in the range of 23.3/ 27.3 to 35.3/ 41.7 mg/mL.Antimicrobial activity of N. lotus was the stronger in ethanol ex-tract than in water extract. This observation has been attributedto the enhanced nature of bioactive compounds in the presenceof ethanol and the stronger extraction power of ethanol. The tra-ditional use of both water and ethanol extracts of N. lotus againstliver damage was supported by the results of this study.

With regard to Nelumbo nucifera, the entire plant has been re-ported to possess rich nutraceutical value (Sridhar and Bhat 2007).Flowers are white to pink, sweet-scented, single, and are 10 to25 cm in diameter. Flowers are reported to be useful to treat bleed-ing disorders and to promote conception. Additionally, flowers arereported to be useful to treat diarrhea, cholera, fever, hepatopa-thy, and hyperdipsia. However, to our knowledge no reports areavailable on the antmicrobial activity of this flower or its extracts.

Plumeria alba Linn. (white champa)Plumeria alba (family: Apocynaceae) is a small laticiferous tree

that is a native of tropical America. The plant has also been foundgrowing in India where it is popularly called Peru. The plantgrows up to 4.5-m high bearing white and fragrant flowers. The

fruits are edible, the seeds possess hemostatic properties, whilethe sap of the stem and leaves are often applied to heal ulcers,herpes, and scabies. The bark is bruised and applied as a plasterover hard tumors, which is also used as a purgative, cardiotonic,diuretic, and hypotensive agent (Radha and others 2008; Zahidand others 2010). The methanolic extract of the flowers of P.alba have shown antimicrobial activity against Bacillus anthracis andP. aeruginosa (Syakira and Brenda 2010; Zahid and others 2010).Different parts of the plant are traditionally used in the treatmentof malaria, leprosy, rheumatism, and abdominal tumors (Syakiraand Brenda 2010).

The essential oils isolated from flowers of P. alba have beenevaluated against Gram-positive S. aureus, B. subtilis, and Gramnegative E. coli, P. aeruginosa, and S. typhi by the agar well diffu-sion method (Zahid and others 2010); Gram-positive bacteria (S.aureus and B. subtilis) were found to be more sensitive to essentialoils. The sensitivity has been attributed to the absence of an outermembrane surrounding the bacterial cell wall that restricts the dif-fusion of hydrophobic components of P. alba essential oil throughthe lipopolysaccharide covering.

Rosa spp. (rose flower)Roses are indigenous to central Asia and are grown as ornamen-

tal plants. Rose flowers have been traditionally used as a medicine,for culinary purposes, and in the preparation of perfumes (due to awarm, intense, rich, and rosy fragrance). Rose flowers were used asmedicine in ancient Assyria, China, Egypt, Greece, India, Persia,and Rome. The flower has 5 petals (or multiples of 5) with nu-merous stamens. Rose petals are aromatic and have various shapesand colors. They enclose androecium and gynoecium, which apartfrom facilitating pollination, possess antibacterial activity as a pro-tection system. Perfumes prepared from rose petals are economi-cally valuable and also have soothing effects (Hirulkar and Agrawal2010). Rose petal jam (prepared in parts of Asia from Rosa indicaL.) is considered to provide a cooling effect on mind and body. Oilobtained from rose flowers has been reported to reduce blood lipidlevels in rats. The hydrating and anti-inflammatory properties ofnatural acids present in rose water are considered to be useful forskin and eye care. Rose petals are also recommended to be usedas mouthwash. The tea decoction prepared from rose petals is rec-ommended to heal breast pain, mastitis, menstrual difficulties, andrestless fetus (Hirulkar and Agrawal 2010). The antioxidant andantimicrobial properties and the chemical compounds present inrose essential oil have been extensively published (Arıdogan andothers 2002; Basim and Basim 2003; Hirulkar and Agrawal 2010).

Petal extract of Rosa canina L. is reported to enhance the effec-tiveness of several antibiotics against methicillin-resistant S. aureusas well as to have strong inhibitory activity against C. albicans(Rossnagel and Willich 2001; Hirulkar and Agrawal 2010). An-thocyanins and proanthocyanidins, tellimagrandin I and rugosin B,carotenoids, plant acids, and essential oils are present in rose petals.Rose oil is reported to contain economically valuable alcohol,such as geraniol (a major constituent) and 1-citronellol (Hirulkarand Agrawal 2010).

Hirulkar and Agrawal (2010) used the agar disc diffusion methodto study the antimicrobial activity of alcoholic, petroleum ether,and aqueous extracts of rose petals against various pathogenic bac-teria. All the dilutions (1:1, 1:2, 1:3) of the 3 types of extractsshowed inhibition against all the tested bacteria with inhibitionzone diameters ranging from 12 to 30 mm. Among the testedbacteria, P. aeruginosa was the most sensitive to the petroleum etherextract of rose petals with an inhibition zone of 29 mm. Results of



this study showed higher inhibitory activity of alcoholic extractsagainst S. pneumoniae (30 mm), E. aerogenes (28 mm), S. epidermidis(25 mm), B. subtilis (30 mm), and P. aeruginosa (32 mm) as com-pared to other bacterial strains. Aqueous extract showed higherinhibitory activity against E.coli (21 mm), E. aerogens (25mm), andB. subtilis (28 mm) as compared to other bacterial strains. It wasfound that alcoholic extract showed higher average antimicrobialactivity (25 mm) when compared to aqueous extract (19 mm) andpetroleum ether extract (18 mm). The authors concluded by stat-ing that rose petals can be potentially used to treat diarrhea, oppor-tunistic infection, and skin infections caused by various pathogenicbacteria.

Koday and others (2010) have reported on the bactericidalproperties of methanol, chloroform, and hexane extracts of 40different medicinal plants against Corynebacterium macginleyi usingthe agar well diffusion assay. From their study, the authors foundmethanolic extract of R. indica petal to possess better antimicrobialactivity against C. macginleyi compared to chloroform and hexaneextracts.

Rumex vesicarius Linn. (bladder dock)Rumex vesicarius (family: Polygonaceae) is a wild edible plant

that grows during spring time (Al- Quran 2009). It is native tosouthwest Asia and North Africa and is cultivated in India, espe-cially in regions of Tripura, West Bengal, and Bihar (Khare 2007).The plant parts are used traditionally in the treatment of variousdiseases, such as tumors, hepatic diseases, indigestion, constipation,heart diseases, pains, spleen disorder, hiccough, flatulence, asthma,bronchitis, dyspepsia, piles, scabies, leucoderma, toothache, nau-sea, and dysentery. The plant also has cooling, laxative, tonic,antibacterial, analgesic, stomachic, appertizer, diuretic, astringent,purgative, and antispasmodic properties. Besides, this plant isused to reduce biliary disorders and to control cholesterol levels(Elegami and others 2001; Atiqur Rahman and others 2004;Lakshmi and others 2009; Mostafa and others 2011).

Antimicrobial activity of different plant parts of this plant againstK. pneumoniae, S. pneumoniae, S. pyogenes, S. aureus, E. coli, and P.aeruginosa was performed using the agar disc diffusion method byMostafa and others (2011). Results of this study demonstratedpotential antibacterial activity (K. pneumoniae, Streptococcus pneu-monia, S. pyogenes, S. aureus, E. coli, and P. aeruginosa) of the flow-ers extracted in different solvent extracts (petroleum ether, ether,chloroform, methanol, and ethanol). Chemical analysis of flowerextracts revealed variations in the presence and amount of activecompounds (flavonoids, anthraquinones, alkaloids, tannins, sterolsand/or triterpenoids, carbohydrates and/or glycosides, chlorides,sulfates, and sublimable substances).

Santolina rosmarinifolia Linn. (green lavender cotton)Santolina rosmarinifolia (family: Asteraceae) is a perennial shrub

found in the Iberian peninsula and southern France (Ioannou andothers 2007). The infusions from flower heads are reported to beused as an antipyretic and have been shown to posses hepatoprotec-tive, antihypertensive, and intestinal anti-inflammatory properties(Novais and others 2004).

The antimicrobial activity of flower heads and leaves of S.rosmarinifolia against S. aureus, S. lutea, B. cereus, E. coli, and C.albicans was determined by Ioannou and others (2007) based onagar disc diffusion and broth dilution assays. From their study,the antimicrobial activity of essential oil from flower heads of S.rosmarinifolia at doses of 1, 5, and 10 μL was found to be strongerthan those from the leaves, with inhibition zone diameters rang-

ing from 8 to 23 mm. From the broth dilution assay performedon S. aureus, the MIC and MBC of 0.3 and 0.6 μL/mL wererecorded indicating strong action of the flower head essential oilagainst this particular bacterium. The chemical composition ofessential oil from flower heads of S. rosmarinifolia (assessed by GC-MS) was shown to be comprised of 42 components represent-ing 92.3% to 94.0% of the oil, with β-eudesmol (13.5%), 1,8-cineole (12.9%), camphor (8.0%), borneol (5.1%), ar-curcumene(4.8%), terpinen- 4-ol (4.5%), and spathulenol (4.4%) as the mainconstituents.

Satureja bachtiarica Bunge. (savory)The genus Satureja (family: Lamiaceae) contains more than 200

species of herbs and shrubs that are widely distributed in theMediterranean region. Aerial parts of Satureja species are used asflavoring agents in a variety of food products as well as for herbalmedicine preparations to treat gastrointestinal disorders (Sonboliand others 2004).

Pirbalouti and others (2010), by employing agar disc diffusionand serial dilution assays, determined the antimicrobial activitiesof some of the Iranian folklore herbs against S. aureus, E. coli,P. aeruginosa, and Klebsiella pneumonia. From the results of theirscreening tests, the ethanolic extract and essential oils of flowersof S. bachtiarica showed strong antibacterial activity against all thetested bacteria with the zone of inhibitions ranging from 12 to23 mm. The MIC values ranged from 0.039 to 10.00 mg/mL.This study showed essential oils to exhibit stronger antibacterialactivity than the ethanol extract.

Tamarix gallica L. (French tamarisk)Tamarix gallica (family: Tamaricaceae) is a halophytic tree found

growing in natural habitats ranging from coastal regions up todeserts. This plant is known to tolerate a wide range of harshenvironmental conditions and can resist abiotic stress, such as salt,high temperature, and dryness (SaIdana and others 2008; Ksouriand others 2009). In certain parts of Asia, the leaves, flowers,and galls of T. gallica are used as therapeutic agents, particularly asanti-inflammatory, antidiarrheic, cicatrizing, and antiseptic agents.They are also used for treating leucoderma, spleen trouble, andeye diseases (Ksouri and others 2009). Besides, the plant parts areused as astringent, aperitif, stimulant of perspiration, and diuretic(SaIdana and others 2008; Ksouri and others 2009).

Based on the inhibition zone measured by the disc diffusion assay(Ksouri and others 2009), the methanolic floral extracts (2, 4, and100 mg/mL) of this plant exhibited antibacterial activities againstS. epidermidis, S. aureus, M. luteus, E. coli, and P. aeruginosa. The flo-ral extracts also showed antifungal activity against Candida spp. withinhibition zones of 6 to 15 mm and 6 to 8.66 mm, respectively.The bioactive compounds present in the flowers were identifiedas phenolic acids (gallic, sinapic, chlorogenic, syringic, vanillic,p-coumaric, and trans-cinnamic acids) and flavonoids (catechin,isoquercetin, quercetin, apigenin, amentoflavone, and flavone).

Thymus daenensis Celak (thyme)The genus Thymus (family: Lamiaceae), is a perennial herb that

has its origin in the Mediterranean region. Leaves and flowers ofThymus species are traditionally used in Iran as tonic and herbaltea, antitussive, antiseptic, carminative, and a treatment for thecommon cold. Thymus oil and extracts (leaves and flowers) arewidely used by the pharmaceutical, perfume, cosmetic, and foodindustries (Nejad Ebrahimi and others 2008; Pirbalouti and others2010).



In one of the experiments conducted by Pirbalouti and oth-ers (2010) on Iranian folklore herbs, the extract and essential oilfrom flowers of T. daenensis have been shown to exhibit strongantibacterial activity against all the test bacteria (S. aureus, E. coli,P. aeruginosa, K. pneumoniae) with inhibition zones ranging from 8to 22 mm. The MIC values of flower extracts ranged from 0.039to 10.00 mg/mL. The results of this study clearly showed essentialoil to have stronger antibacterial activity than the solvent (ethanol)extracts.

Zingiber mioga (Thunb.) Roscoe (Myoga)Zingiber mioga (family: Zingiberaceae), a native to eastern Asia,

is widely cultivated in Japan as a perennial herb. The stalks ofthis plant extend up to 1 m, with slender leaves reaching 30 cmhaving pine-cone-like flower buds ranging up to 7 to 10 cm inlength. In Japan, “myogabochi,” a traditional food (buns filled withsweetened bean paste) is wrapped with the leaves of this plant tobe preserved for a long period. Flower buds have a unique andpungent flavor, attributed to the presence of diterpene dialde-hyde compound, 2-alkyl-3-methoxypyrazine and (E)-8-β-(17)-epoxylabd-12-ene-15, 16 dial (myogadial). Due to their pungentflavor, the flower buds have been used as a spice and to pre-pare pickles in Japan (Sakakibara and others 1991; Abe and others2002).

Abe and others (2004) screened for the potential antimicrobialactivities of the flower buds against a wide range of bacteria, yeasts,and molds by employing the agar disc diffusion assay. The resultsof their study revealed ethyl acetate extracts of flower buds toexhibit appreciable antimicrobial activity with an inhibition zoneof 8 mm, while the methanol extract showed minimal activity withan inhibition zone of 2 mm. Additionally, MICs of the 3 diterpenedialdehydes (myogadial, galanal A, and galanal B) isolated fromthe ethyl acetate extract were measured using the serial dilutionmethod. From the results, myogadial, galanal A, and galanal Bwere found to be effective against Gram-positive bacteria andyeast with myogadial (MIC = 25 to 125 μg/mL) showing higheractivity compared to galanal A and B (MIC = 200 to 500 μg/mL).The reason for the antimicrobial activity has been attributed bythe authors to the presence of galanal A and B that were presentin the 1, 6 positions of the aldehyde groups, with the introductionof a hydroxyl group in their molecules.

Major Bioactive Compounds in Flower ExtractsBioactive compounds isolated from flowers and their extracts

have shown potential antimicrobial activities. The isolated com-pounds are classified into different groups, such as phenolics, ter-penoids, essential oils, glycosides, and alkaloids. A few of these arediscussed in the preceding text below.

PhenolicsAmong the various phenolic compounds, flavonoids are found

abundantly in plant-derived foods (Denny and Buttriss 2007).Flavonoids (consisting of a central 3-ring structure), are majorphenolic compounds that play a pivotal role in plants, such asprotection against UV, pigmentation, stimulation of nitrogen fix-ing nodules, and disease resistance (Pierpoint 2000; Denny andButtriss 2007). This group of compounds can occur as glycosidestoo. Flavonoids are known to exhibit rich antioxidant, anticar-cinogenic, and anti-inflammatory properties. Besides, flavonoidsare known to possess antimicrobial activities due to their ability toform complexes with extracellular and soluble proteins and micro-bial cell wall (Tsuchiya and others 1996; Cowan 1999; Grotewold2006).

Flavonols, flavones, isoflavones, flavanones flavan-3-ols (cate-chins and proanthocyanidins), and anthocyanins, are some ofthe subcategories of flavonoids (Toda and others 1989; Cowan1999; Grotewold 2006). Anthocyanins are responsible for thecharacteristic red, blue, or purple colors of flowers. Flavonols(quercetin, kaempferol, and myricetin) are widespread flavonoidsfound in plants, which have potential antimutagenic, anticar-cinogenic, and antihypertensive activities. Flavanones are foundin abundance in citrus fruits, which impart bitter flavor to thefruit peels (Denny and Buttriss 2007; Bernhoft 2010). The ma-jor flavonoid constituents reported in flower extracts includes:quercetin, kaempferol, catechins, proanthocyanidins, apigenin,and anthocyanins (Quarenghi and others 2000; Drewes and VanVuuren 2008; Dung and others 2008; Nakhaei and others 2008;Ksouri and others 2009; Zhao and others 2009; Chouhan andSingh 2010; Hirulkar and Agrawal 2010; Lachumy and others2010; Bhalodia and others, 2011; Mostafa and others 2011).

Phenolic acids and quinonesPhenolic compounds as phenolic acids (gallic, sinapic, chloro-

genic, syringic, vanillic, p-coumaric, and trans-cinnamic acids) arealso found in flower extracts (Ksouri and others 2009).

Quinones are highly reactive compounds that have aromaticrings with 2 ketone substitutions. The antimicrobial activity ofquinones involve forming of complex with proteins (surface-exposed adhesins), cell wall polypeptides, and membrane-boundenzymes, leading to inactivation of function of the proteins (Sternand others 1996; Cowan 1999). Besides, quinones are capable ofrendering a substrate unavailable to microorganisms, thus inhibit-ing their growth. Mostafa and others (2011) described the pres-ence of anthraquinones in various extracts of R. vesicarius flowers,which served as one of the antimicrobial compounds against thetested microorganisms (K. pneumonia, S. pneumoniae, S. pyogenes, S.aureus, E. coli and P. aeruginosa). In one of the experiments con-ducted by Bhalodia and others (2011) on hydro-alcohol and chlo-roform extracts of C. fistula flowers, anthraquinones present in theextracts was found to exhibit rich antimicrobial activities, whichwere found to be active against some sensitive bacteria and fungi(S. aureus, S. pyogenes, E. coli, P. aeruginosa, A. niger, A. clavatus, andC. albicians).

TanninsTannins are a group of polymeric phenolic compounds

widespread in plants. Tannins are known to exhibit astringentproperties and are synthesized by condensation of flavan deriva-tives or polymerization of quinone units (Haslam 1996; Cowan1999). Tannins form complex with microbial adhesins, enzymes,and cell envelope transport proteins, leading to inactivation ofthese proteins and inhibition of microbial growth (Haslam 1996;Stern and others 1996). Scientific evidences showed tannins to beeffective against filamentous fungi, yeasts, and bacteria (Brownleeand others 1990; Scalbert 1991; Cowan 1999). Some examples offlowers with presence of high tannin include: Allium spp. (Chehre-gani and others 2007), C. fistula (Bhalodia and others 2011), E.elatior (Lachumy and others 2010) and R. vesicarius (Mostafa andothers 2011).

Terpenoids and essential oilsEssential oils are secondary metabolites containing a mixture of

compounds that are based on 5 carbon isoprene structure (ter-penes) occurring as diterpenes, triterpenes, tetraterpenes (C20,C30, and C40), hemiterpenes (C5), and sesquiterpenes (C15)(Cowan 1999). The antimicrobial activity of terpenes involves



disruption of cell membrane by their lipophilic constituents. Pre-liminary phytochemical screening on essential oils extracted fromthe flowers of C. macropodum (Ebrahimabadi and others 2010), C.trifurcatum (Sassi and others 2008b), C. operculatus (Dung and others2008), L. japonica (Rahman and Kang 2009), and S. rosmarinifolia(Ioannou and others 2007) have shown monoterpenes, sesquiter-penes, and their oxygenated derivatives to be major constituents,which contribute substantially to antimicrobial activities.

Terpenes (comprising of >30000 different compounds) aretermed terpenoids when they contain additional elements, typ-ically oxygen. Reports are available wherein bacteria and fungihave been shown to be sensitive to terpenoids (Tassou and others1995; Taylor and others 1996; Cowan 1999). Terpenoids presentin essential oils were effective against L. monocytogenes (Aureli andothers 1992; Cowan 1999). Terpenoid contents reported in flowerextracts might contribute to the observed antimicrobial activitiesof the flower extracts as observed for C. fistula (Bhalodia and others2011), C. morifolium (Zhao and others 2009), E. elatior (Lachumyand others 2010), and Rosa spp. (Hirulkar and Agrawal 2010).

Plant sterols (also terpenoids), have the ability to reduce totaland low-density lipoprotein cholesterol level in plasma (Dennyand Buttriss 2007). Flowers of C.operculatus and R. vesicarius arereported to contain sterols (Dung and others 2008; Mostafa andothers 2011). However, not much research reports are available onthese aspects.

GlycosidesGlycosides are composed of a variety of secondary metabolites

bound to a mono- or oligosaccharide or to uronic acid. The partof saccharide or uronic acid is known as glycone, and the backboneis known as aglycone. Cardiac glycosides, cyanogenic glycosides,glucosinolates, saponins, and anthraquinone glycosides, being dif-ferent in their aglycone structures, are the main groups of glyco-sides (Bernhoft 2010). Investigations carried out on the flowers ofC. fistula, C. Juncea, and R. vesicarius have clearly demonstrated thepresence of glycosides in their extracts (Chouhan and Singh 2010;Bhalodia and others 2011; Mostafa and others 2011).

AlkaloidsAlkaloids are heterocyclic, nitrogen-containing compounds,

with potential clinical properties. Alkaloids have bitter taste andare present in threshold level in plants (Bernhoft 2010). Flowers ofC. juncea and R. vesicarius have been reported to contain alkaloids(Chouhan and Singh 2010; Mostafa and others 2011).

Even though a wide range of bioactive compounds might bepresent in flowers, still there is a lack of detailed investigationscarried out on these aspects. These needs to be explored furtherto confirm the antimicrobial activities exhibited.

Conclusion and OutlookEdible flowers from ornamental, cultivated, as well as wild plants

have high potential to be explored as natural resources of antimi-crobial agents. Exploring these underutilized flowers by providingadequate scientific evidence might enhance the chances of devel-oping new conventional and natural antimicrobial agents (drugsas well as food preservatives) and be good alternatives to syntheticchemicals. Screening for the potential bioactive compounds ca-pable of exhibiting antimicrobial activities might provide morein-depth details. Further studies are warranted to identify variousmechanisms involved in the antimicrobial actions exhibited by thebioactive compounds present in flowers (as to how they interactwith a microorganism to cause inhibitory or lethal effects). As

flower extracts and their essential oils have been proven to possessantimicrobial activities, these can be incorporated into develop-ing new and novel biopolymer-based edible films, especially forpreserving fresh produce.

Based on the reports available from in vitro studies conductedtill date, high extraction yields and strong antimicrobial activitieshave been demonstrated by plant materials extracted in methanol(Quarenghi and others 2000; Annegowda and others 2011; Mannand others 2011). However, methanol can be highly toxic to hu-mans and livestock and cannot be considered as a food gradesolvent. In comparison to methanol, solvents such as ethanoland water, which have also exhibited appreciable antimicrobialactivities, can be considered safe and results generated by us-ing these solvents can be beneficial for food and pharmaceuticalapplications.

Flower extracts and their essential oils have many traditionaluses, such as in the preparation of foods and herbal remedies,with minimal known “side-effects” on human health. Being nat-ural, they are accepted to be highly safe for consumption. Of late,edible flowers are extensively being explored for commercial ap-plications in food industries such as for development of floral teas,beverages, functional foods, and bakery products. However, todate, research works undertaken on issues pertaining toward safetyand toxicity of flower extracts and their essential oils are scarce.The effectiveness of flower extracts against a wider spectrum ofpathogenic microorganisms needs to be investigated before beingused for food preservation or medicinal purposes. In addition,clinical effects of the floral extracts and their essential oils under“in vivo” conditions as well as in food systems need to be studiedto evaluate in detail their potential effectiveness as antimicrobialagents as well as presence of any acute or chronic effects.

The sensory qualities of a foodstuff are related to consumers’ ac-ceptance. With regard to flowers, sensory qualities are attributableto chemical constituents, particularly the volatile and colored com-pounds. The chemical compounds will affect the organolepticalattributes (desirable or undesirable with regard to appearance, col-ors, tastes, and odors) of food into which the flower extract oressential oil are being incorporated. The flowers with intense char-acteristic colors or pleasant aroma may be feasible to be exploitedas a food colorant or food fragrance.

Based on the available literature, it is evident that still a widegap persists in the scientific knowledge with regard to many otherindigenous flowers (common and wild flowers) used for culinaryand therapeutic purposes, which include: banana flowers, coconutflowers, cheddar pink, rosebay willowherb, champika, chickweed,Dutch clover, sweet snow, and others (just to name a few). Thismerits further investigation to search for potential antimicrobialactivities and for prospective food industry applications.

AcknowledgmentsThe authors gratefully acknowledge anonymous referees and

Scientific Editor (Prof. Dr. Manfred Kroger) for comments andconstructive suggestions provided for improving the quality of thismanuscript. First author thanks Inst. of Postgraduate Studies, Univ.Sains Malysia for the fellowship provided. Individual research fundprovided as an RU grant (Nr 1001/PTEKIND/814139,USM) forthe corresponding author is also gratefully acknowledged.

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Flower Extracts and Their Essential Oils as Potential Antimicrobial Agents for Food Uses and...

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