Chemical Composition and Inhibitory Effect of Essential Oil and Organic Extracts of Cestrum Nocturnum L. on Food-borne Pathogens

Original article

Chemical composition and inhibitory effect of essential oil and

organic extracts of Cestrum nocturnum L. on food-borne pathogens

Sharif M. Al-Reza, Atiqur Rahman & Sun Chul Kang*

Department of Biotechnology, Daegu University, Kyoungsan, Kyoungbook 712-714, Korea

(Received 14 October 2008; Accepted in revised form 28 Jan 2009)

Summary In this study, we examined the chemical compositions of essential oil and tested the efficacy of oil and organic

extracts of Cestrum nocturnum L. against food-borne pathogens. The chemical compositions of the oil was

analysed by gas chromatography-mass spectrometry (GC-MS). Forty-seven compounds representing

93.28% of the total oil were identified. The oil [5 lL of 1:5 (v ⁄ v) dilution of oil with methanol] and organic

extracts of hexane, chloroform, ethyl acetate and methanol (300 lg per disc) of C. nocturnum displayed a

great potential of antibacterial activity against Staphylococcus aureus (ATCC 6538 and KCTC 1916), Listeria

monocytogenes (ATCC 19166 and ATCC 15313), Bacillus subtilis ATCC 6633, Pseudomonas aeruginosa

KCTC 2004, Salmonella typhimurium KCTC 2515 and Escherichia coli ATCC 8739. Also the oil had strong

detrimental effect on the viable count of the tested bacteria. The results obtained from this study may

contribute to the development of new antimicrobial agents with potential applications in food industries as

natural preservatives to control food-borne pathogens.

Keywords Antibacterial activity, benzyl alcohol, Cestrum nocturnum L., essential oil, food-borne pathogens, phenylethyl alcohol.

Introduction

Global interest in bio-preservation of food systems hasrecently been increased because of great economic costsof deterioration and poisoning of food products by foodpathogens and is often responsible for the loss of qualityand safety. Concern over pathogenic and spoilagemicro-organisms in foods is increasing because of theincrease in outbreaks of food borne disease. Currentlythere is a growing interest to use natural antibacterialcompounds, like extracts of herbs and spices for thepreservation of foods. Plant-derived essential oils andextracts of various species of edible and medicinalplants, herbs, and spices have long been used as naturalagents for food preservation in food and beveragesbecause of the presence of antimicrobial compounds(Nychas et al., 2003). In general, plant derived essentialoils are considered as non-phytotoxic compounds andpotentially effective against micro-organisms. In thiscontext, the identification and evaluation of naturalproducts for the control of these pathogens, to assureconsumers a safe, wholesome, and nutritious foodsupply, can be considered an important internationalchallenge.

With the increase of bacterial resistance to antibiotics,there is considerable interest to investigate the antimicro-bial effects of essential oils and different extracts against arange of bacteria, to develop other classes of naturalantimicrobials useful for the infection control or for thepreservation of food (Bakri & Douglas, 2005). The Grampositive bacterium Staphylococcus aureus is mainlyresponsible for post-operative wound infections, toxicshock syndrome, endocarditis, osteomyelitis and foodpoisoning (Mylotte et al., 1987). Listeria monocytogenesis responsible for the severe food-borne illness, listeriosis,which has been recognised to be one of the emergingzoonotic diseases during the last two decades (Farber,2000). The Gram negative bacterium Escherichia coli ispresent in human intestines and causes urinary tractinfection, coleocystitis or septicemia (Singh et al., 2000).Cestrum nocturnum L. is a garden shrub from the

family Solanaceae, the flowers of which exude a specialsweet fragrance at night, the main reason for its folknames night cestrum, lady of the night, night-bloomingjessamine, and night blooming jasmine. It is widelynaturalised in tropical and subtropical regions through-out the world, including Australia, Southern China andthe Southernmost United States. It is also cultivated inBangladesh in home yards and gardens. Several phyto-chemical studies have demonstrated the presence ofimportant bioactive compounds in different parts of the

*Correspondent: Fax: +82 53 850-6559;

e-mail: [email protected]

International Journal of Food Science and Technology 2009, 44, 1176–11821176

doi:10.1111/j.1365-2621.2009.01939.x

� 2009 The Authors. Journal compilation � 2009 Institute of Food Science and Technology

plant: alkaloids, flavonol glycosides, steroidal saponins,fatty acids, essential oils, phenols, and others (Bouchb-aver et al., 1995).Practitioners use the plant externally for skin disor-

ders, but several scientific reports demonstrate that itexhibits a wide spectrum of pharmacological activitywhen administered systemically or in isolated organpreparations. For example, it is used to treat arterialhypotension and as an analgesic, abortive, diuretic,antispasmodic, dyspeptic, antiviral, and smooth musclerelaxant; it also has negative inotropic and chronotropicactions (Pe¢rez-Saad & Buznego, 2008).Most of the species of Cestrum have found several

applications in folk medicine. Cestrum parqui is used inChilean folk medicine as antifebrile and for the treatmentof fever and inflammation.Chinese people use leaves ofC.nocturnum for their pharmacological significance in burnsand swellings. It is also used for treating epilepsy and asstupefying charm medicine in West Indian Islands. Thevolatile oil of the species is known to be mosquitorepellent and henceC. nocturnum andC. diurnum are usedto prevent malaria in several African Nations (Ntoniforet al., 2006). The plants of the genus have further founduse in perfumery, as ornamental plants, floral scentproduction etc. However, there is no report available inthe literature on the analyses of essential oil from flowerparts of C. nocturnum and its antibacterial propertyagainst the food-borne pathogenic bacteria.Therefore, the aims of the present study were (1) to

examine the chemical composition of the essential oil ofC. nocturnum L. by gas chromatography-mass spec-trometry (GC-MS); and (2) to evaluate the antibacterialactivity of essential oil from flower parts of C. noctur-num L. and various organic extracts (hexane, chloro-form, ethyl acetate and methanol) against a diverserange of food-borne pathogenic bacteria with emphasisfor the possible future use of the essential oil and plantextracts as an alternative to chemical bactericides forfood preservation.

Materials and methods

Plant material

The flowers of C. nocturnum were collected from IslamicUniversity Campus, Kushtia, Bangladesh in December2007. The taxonomic identification of plant materialswas confirmed by a senior plant taxonomist Dr M. OliurRahman, Bangladesh National Herbarium, Dhaka,where a voucher specimen (DACB 32562) has beendeposited.

Isolation of the essential oil

The air-dried flower parts (200 g) of C. nocturnum weresubjected to hydrodistillation for 3 h using a Clevenger

type apparatus. The oil was dried over anhydrousNa2SO4 and preserved in a sealed vial at 4 �C untilfurther analysis.

Preparation of organic extracts

The air-dried flower parts (50 g) of C. nocturnum wereextracted with hexane, chloroform, ethyl acetate andmethanol separately at room temperature and thesolvents were evaporated by vacuum rotary evaporator(EYELA N1000). The extraction process yielded inhexane (7.5 g), chloroform (6.6 g), ethyl acetate (5.4 g)and methanol (6.3 g) extracts. Solvents (analyticalgrade) for extraction were obtained from commercialsources (Sigma–Aldrich, St Louis, MO, USA).

Gas chromatography-mass spectrometry analysis

The GC-MS analysis of the essential oil was performedusing a GC-MS (Model QP 2010, Shimadzu, Japan)equipped with a ZB-1 MS fused silica capillary column(30 m · 0.25 i.d., film thickness 0.25 lm). For GC-MSdetection, an electron ionisation system with ionisationenergy of 70 eV was used. Helium gas was used as acarrier gas at a constant flow rate of 1 mL min)1.Injector and mass transfer line temperature were set at220 and 290 �C, respectively. The oven temperature wasprogrammed from 50 to 150 �C at 3 �C min)1, then heldisothermal for 10 min and finally raised to 250 �C at10 �C min)1. Diluted samples (1 ⁄100, v ⁄v, in methanol)of 1 lL was manually injected in the split less mode. Therelative percentage of the oil constituents was expressedas percentage by peak area normalisation.The identity of the components of the essential oil was

assigned by comparison of their retention indices,relative to a series n-alkane indices on the ZB-1 capillarycolumn and GC-MS spectra from the Wiley 6.0 MS dataand literature data (Adam, 2001).

Micro-organisms

The following food-borne pathogenic bacterial strainswere used in the antibacterial test: S. aureus ATCC6538, S. aureus KCTC 1916, L. monocytogenes ATCC19166, L. monocytogenes ATCC 15313, Bacillus subtilisATCC 6633, Pseudomonas aeruginosa KCTC 2004,Salmonella typhimurium KCTC 2515, E. coli ATCC8739, E. coli O157:H7 ATCC 43888, Enterobacteraerogenes KCTC 2190 and S. enteritidis KCTC 12021.The strains were obtained from the Korea Food andDrug Administration (KFDA), Daegu, Korea. Activecultures for experimental use were prepared by trans-ferring a loopful of cells from stock cultures to flasksand inoculated in Luria-Bertani (LB) broth medium at37 �C for 24 h. Cultures of each bacterial strains weremaintained on LB agar medium at 4 �C.

Antibacterial effects of C. nocturnum L. S. M. Al-Reza et al. 1177

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Antibacterial activity assay

The dried extracts were dissolved in the same solventused for their extraction to a final concentration of30 mg mL)1 and sterilised by filtration through 0.45 lmMillipore filters (Millipore Corp., Bedford, MA, USA).The antibacterial test was then carried out by agar discdiffusion method (Murray et al., 1995) using 100 lL ofstandardised inoculum suspension containing107 CFU mL)1 of bacteria. The essential oil was diluted1:5 (v ⁄v) with methanol and aliquots of 5 lL werespotted onto the filter paper discs; while 10 lL of30 mg mL)1 of each organic extract (300 lg per disc)was applied on the filter paper discs (6 mm diameter)and placed on the inoculated LB agar. Negative controlswere prepared using the same solvents employed todissolve the samples. Standard reference antibiotics,tetracycline and streptomycin (10 lg per disc, each fromSigma-Aldrich Co., St. Louis, MO, USA), were used aspositive controls for the tested bacteria. The plates wereincubated at 37 �C for 24 h. Antibacterial activity wasevaluated by measuring the diameter of the zones ofinhibition against the tested bacteria. Where, 7–10 mm,weak inhibition; 11–14 mm, moderate inhibition;>15 mm, strong inhibition. Each assay in this experi-ment was replicated three times.

Minimum inhibitory concentration

Minimum inhibitory concentration (MIC) of essentialoil and extracts of hexane, chloroform, ethyl acetate andmethanol, were tested by standard NCCL method(NCCLS, 2000). Active cultures for MIC determinationwere prepared by transforming a loopful of cells fromthe stock cultures to flasks and inoculated in LBmedium and incubated at 37 �C for 24 h. The cultureswere diluted with LB broth to achieve optical density of107 CFU mL)1 for the test organisms at 600 nm byUV ⁄Vis Spectrophotometer Optizen 2120UV & OptizenIII (Shin et al., 2007). Dilutions, to get the finalconcentration ranging from 0 to 1000 lg mL)1 ofessential oil and extracts of hexane, chloroform, ethylacetate and methanol in LB broth medium wereprepared in a 96-well microplates. Finally, 20 lL inoc-ulum of each bacteria strain (107 CFU mL)1) wasinoculated on to the microplates and the tests wereperformed in a volume of 200 lL. The plates wereincubated at 37 �C for 24 h. The lowest concentration ofthe test samples, which did not show any visual growthof tested organisms after macroscopic evaluation, wasdetermined as MIC, which was expressed in lg mL)1.

Effect of essential oil on viable counts of bacteria

For viable counts, each of the tubes containingbacterial suspension (approximately 107 CFU mL)1)

of L. monocytogenes ATCC19166, L. monocytogenesATCC15313, S. aureus ATCC 6538 and P. aeruginosaKCTC 2004 in LB broth medium was inoculated withthe MIC of the essential oil in 10 mL LB broth, andkept at 37 �C (Bajpai et al., 2008). Samples for viablecell counts was taken out at 0, 20, 40, 60, 80 and 100 mintime intervals. Enumeration of viable counts on LBplates were monitored as follows: after incubation, 1 mLof the resuspended culture was diluted into 9 mL bufferpeptone water, thereby diluting 10 fold. In total, 0.1 mLsample of each treatment was diluted and spread on thesurface of LB agar. The colonies were counted after 24 hof incubation at 37 �C. The controls were inoculatedwithout essential oil for each bacterial strain with sameexperimental condition as mentioned above.

Statistical analysis

The essential oil and different organic extracts wereassayed for antibacterial activity. Each experiment wasrun in triplicate, and mean values were calculated. AStudent’s t-test was computed for the statistical signif-icance of the results.

Results

Chemical composition of the essential oil

The hydrodistillation of the air-dried flowers of C.nocturnum gave the dark yellowish oil with a yield of0.34% (w ⁄w). Gas chromatography-mass spectrometryanalyses of the oil led to the identification of 47 differentcompounds, representing 93.28% of the total oil. Theidentified compounds are listed in Table 1 according totheir elution order on a ZB-1 capillary column. Themajor compounds detected were phenylethyl alcohol(27.45%), benzyl alcohol (12.21%), eicosane (5.62%),eugenol (5.59%), n-tetracosane (4.42%), caryophylleneoxide (3.15%), 1-hexadecanol (2.75%), methoxyeugenol(2.45%) and benzaldehyde (2.32%). Hexadecanoic acid(1.71%), 1-nonadecanol (1.65%), heneicosane (1.55%),methyl anthranilate (1.44%), nonadecene (1.37%), ner-olidol (1.31%), tetradecanal (1.28%) and citronellal(1.23%) were also found to be the minor components ofC. nocturnum oil in the present study.

Antibacterial activity

The in vitro antibacterial activity of essential oil andvarious extracts (hexane, chloroform, ethyl acetate andmethanol) of C. nocturnum against the employed bac-teria was qualitatively assessed by the presence orabsence of inhibition zones. According to the resultsgiven in Table 2, a total of eleven food-borne patho-genic bacteria, including five Gram-positive and sixGram-negative bacteria were tested. The oil exhibited

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International Journal of Food Science and Technology 2009 � 2009 The Authors. Journal compilation � 2009 Institute of Food Science and Technology

antibacterial activity against all five Gram-positive andthree Gram-negative bacteria at the concentration of5 lL of 1:5 (v ⁄v) dilution with methanol. The oilexhibited a potent inhibitory effect against S. aureus(ATCC 6538 and KCTC 1916), L. monocytogenes(ATCC 19166 and ATCC 15313), B. subtilis ATCC6633, P. aeruginosa KCTC 2004, S. typhimurium KCTC2515 and E. coli ATCC 8739 with diameter of inhibitionzones ranging from of 9.8�18.2 mm, as shown inTable 2. Various organic extracts of C. nocturnum alsorevealed a great potential of antibacterial activityagainst all five Gram-positive and three Gram-negativebacteria (P. aeruginosa KCTC 2004, S. typhimuriumKCTC 2515 and E. coli ATCC 8739), at the concentra-tion of 300 lg per disc (Table 2). Methanol extractshowed the strongest antibacterial effect against S.aureus (ATCC 6538 and KCTC 1916), L. monocytogenesATCC 19166 and B. subtilis ATCC 6633 with theirrespective diameter zones of inhibition of 18.1, 18.2, 17.0and 16.4 mm, as compared with standard drug strepto-mycin. On the other hand, hexane, chloroform and ethylacetate extracts showed interesting antibacterial effectwith inhibition zones in the range of 10.1�13.2,10.1�14.1 and 11.1�16.2 mm, respectively. In thisstudy, in some cases, the oil and organic extracts(chloroform, ethyl acetate and methanol) exhibitedhigher antibacterial activity compared with streptomy-cin, while tetracycline showed higher activity in someother cases than the essential oil and solvent extracts.The blind control did not inhibit the growth of the testedbacteria. The oil and various extracts (hexane, chloro-form, and ethyl acetate) from C. nocturnum exhibited amoderate inhibitory effect against P. aeruginosa KCTC2004, S. typhimurium KCTC 2515 and E. coli ATCC8739, with diameter zones of inhibition in the range of9.8�13.3 and 10.1�13.2 mm, respectively. No inhibi-tory effect was observed against E. coli O157:H7 ATCC43888, E. aerogenes KCTC 2190 and S. enteritidisKCTC 12021 in all cases.

Minimum inhibitory concentration

As shown in Table 3, the MIC values for the oil werefound lower for L. monocytogenes (ATCC 19166 and

Table 1 Chemical composition of the essential oil from flower parts

Cestrum nocturnum L

Compound RIa Composition (%)

Hydrocarbons

8-Methyl-1-unde cene 1140 0.38

n-Hexadecane 1612 0.41

Nonadecene 1918 1.37

Eicosane 2009 5.62

He ne ico sane 2109 1.55

n-Tetracosane 2407 4.42

Aldehydes and ketones

Benzaldehyde 982 2.32

Geranyl acetone 1420 0.12

Benzofuranone 1426 0.32

Dicyclohexyl ketone 1576 0.45

Tetrade canal 1601 1.28

Pentade canal 1701 1.13

He xade canal 1800 0.47

Octade canal 1999 0.91

Alcohols

Benzyl alcohol 1036 12.21

Phenyl ethyl alcohol 1136 27.45

Cycloheptanol 1306 0.48

n-Undecanol 1357 0.44

Dodecanol 1457 0.44

Pentadecanol 1755 0.32

1-Hexadecanol 1854 2.75

Heptadecanol 1954 0.62

E.E-2, 1 3-Octadecadien-1-ol 2069 0.34

1-Nonadecanol 2153 1.65

Phenols

Durenol 1354 0.45

Eugenol 1392 5.59

Methoxyeugenol 1581 2.45

Fatty adds

Tetradecanoic acid 1769 0.89

Hexadecanoic acid 1968 1.71

Pentadecanoic acid 2101 0.23

(Z)-9-Octadecenoic acid 2175 0.37

9,12-Octadecadienoic acid 2183 0.65

Eicosanoic acid 2366 1.23

Esters

Vinyl cyclohexanecarboxylate 1137 0.35

Methyl anthranilate 1372 1.44

Famesyl acetate 1834 0.32

Monoterpene

Azulene 1386 0.33

Oxygenated monoterpene

p-Menth-8-en-2-ol 1196 0.36

Sesquiterpenes

Famesene 1320 0.79

Caiyophyllene 1494 0.68

Oxygenated sesquiterpenes

Caiyophyllene oxide 1567 3.15

Nerolidol 1564 1.31

Phytol 2045 0.93

Nitrogenous compound

Indole 1174 0.43

Table 1 (Continued)

Compound RIa Composition (%)

Monoterpenoid

Citronellal 1125 1.23

Others

trans-Z-d-Bisabolene ep oxide 1531 0.75

2, 5-Dim etho xy ac et anili de 1671 0.19

Total 93.28

aRetention index relative to n-alkanes on ZB-1 capillary column.



ATCC 15313) S. aureus ATCC 6538 and P. aeruginosaKCTC 2004 (62.5�125 lg mL)1) than for S. aureusKCTC 1916, B. subtilis ATCC 6633, S. typhimuriumKCTC 2515 and E. coli ATCC 8739(250�500 lg mL)1). On the other hand, MIC valuesof various solvent extracts against the tested bacteriawere found in the range of 62.5�500 lg mL)1 (Table 3).Methanol and ethyl acetate extracts showed higher

antibacterial activity by MICs than hexane and chloro-form extracts. In this study, the Gram-positive bacteriawere found to be more susceptible to the essential oiland various solvent extracts than did Gram-negativebacteria.

Effect of essential oil on viable counts of bacteria

Based on the susceptibility, further, elaborative studycarried out on L. monocytogenes ATCC19166, L.monocytogenes ATCC15313, S. aureus ATCC 6538and P. aeruginosa KCTC 2004, displayed differentsensitivities of the essential oil. The effects of essentialoil on the growth of all the tested bacterial strainsdemonstrated the reduced viability of the testedbacteria at MIC concentration of the essential oil.Complete inhibition of both strains of L. monocytog-enes ATCC19166 and L. monocytogenes ATCC15313was observed at MIC concentration of the essential oilat 20 and 40 min exposure, respectively. Also the steepdecline in CFU numbers was observed at 60 minexposure against S. aureus ATCC 6538 and P.aeruginosa KCTC 2004. Exposure of 80 min of theessential oil MIC concentration revealed completeinhibition of CFU numbers against all the bacterialstrains tested (Fig. 1).

Discussion

Plant based secondary metabolites such as essential oiland extracts are widely used in the food industry and areconsidered generally recognised as safe (GRAS). Theyusually contain more than a single compound with

Table 2 Antibacterial activity of essential oil and various extracts of Cestrum nocturnum L. against food-borne pathogenic and spoilage bacteria

Zones of inhibition (mm)

Micro-organism Essential oila

Various extractsb Antibioticsc

Hexane CHCl3 EtOAc MeOH TC SM

S. aureus ATCC 6538 18.2 ± 1.1 13.1 ± 0.7 14.0 ± 1.6 16.2 ± 1.5 18.1 ± 1.4 17.8 ± 0.6 13.2 ± 0.6

S. aureus KCTC 1916 16.2 ± 1.5 13.2 ± 0.5 13.6 ± 1.2 15.6 ± 1.2 18.2 ± 1.2 18. 1 ± 0.6 13. 1 ± 0.5

L. monocytogenes ATCC 19166 16.3 ± 0.9 12.1 ± 1.1 14.1 ± 0.5 15.2 ± 1.0 17.0 ± 1.2 17.2 ± 0.7 12.6 ± 0.7

L. monocytogenes ATCC 15313 14.1 ± 1.1 12.5 ± 0.7 14. 1 ± 1.1 14.1 ± 1.2 16.7 ± 1.2 18.4 ± 0.5 16.2 ± 1.2

B. subtilis ATCC 6633 15.3 ± 0.7 13.2 ± 0.8 12.3 ± 1.2 13.6 ± 0.6 16.4 ± 0.7 18.3 ± 0.5 14.3 ± 0.6

P. aeruginosa KCTC 2004 13.3 ±1.2 11.6 ± 1.1 11. 0 ± 1.2 13.2 ± 1.1 15.1 ± 1.4 17.9 ± 1.2 18.0 ± 0.5

S. typhimurium KCTC 2515 9.8 ± 1.5 10.1 ± 1.1 10.2 ± 1.2 12.3 ± 1.6 13.2 ± 1.1 18.0 ± 0.6 13.3 ± 0.6

E. coli ATCC 8739 10.0 ± 0.6 nd 10.1 ± 1.2 11.1 ± 0.7 11. 8 ± 1.7 153 ± 1.2 14.0 ± 0.7

E. coli 0157H7ATCC43888 nd nd nd nd nd 16.3 ± 0.5 12.3 ± 1.1

E. aerogenes KCTC 2190 nd nd nd nd nd 15 .1 ± 1.0 10.0 ± 0.5

S. enteritidis KCTC 12021 nd nd nd nd nd 18.3 ± 1.3 11.3 ± 0.6

Values are given as mean ± SD (n = 3).

nd, not detected.aDiameter of inhibition zones of essential oil including diameter of disc 6 mm (tested at a volume of 5 lL per disc).bVarious extract (300 lg ⁄ disc) Where, 7–10 mm, weak inhibition, 11–14 mm, moderate inhibition, >15 mm, strong inhibition.cStandard antibiotics: TC, tetracyclme and S.M, streptomycin (10 lg per disc).

Table 3 Minimum inhibitory concentration of essential oil and various

extracts of Cesturm nocturnum L. against food-borne pathogenic and

spoilage bacteria

Minimum inhibitory concentration (MIC)a

Micro-organism Essential oil

Various extracts

Hexane CHCl3 EtOAc MeOH

S. aureus ATCC 6538 12.5 25.0 12.5 62.5 62.5

S. aureus KCTC 1916 25.0 25.0 25.0 25.0 12.5

L. monocytogenes

ATCC 19166

62.5 25.0 12.5 62.5 62.5

L. monocytogenes

ATCC 15313

12.5 50.0 25.0 12.5 12.5

B. subtils ATCC 6633 25.0 25.0 25.0 12.5 12.5

P. aeruginosa KCTC 2004 12.5 50.0 25.0 25.0 25.0

S. typhimurium KCTC 2515 25.0 50.0 50.0 25.0 50.0

E. coli ATCC 8739 50.0 nd 50.0 50.0 50.0

E. coli 0157H7ATCC43888 nd nd nd nd nd

E aerogenes KCTC 2190 nd nd nd nd nd

S enteritidis KCTC 12021 nd nd nd nd nd

nd, not detected.aMinimum inhibitory concentration (values in lg mL)1).



antimicrobial activity. Hence, using essential oil ⁄ extractshas, as a consequence, to take advantage of all activecompounds present in essential oil ⁄ extracts (Hao et al.,1998). Plants-derived essential oils because of theirantimicrobial content possess potential significance asnaturally occurring agents for food preservation. Manyvolatile compounds naturally occurring in variousessential oils possess strong antibacterial activities,thereby considering as natural antibacterial agents toinhibit the growth of food-borne pathogens (Cowan,1999). The renewal of interest in food industry, andincreasing consumer demand for effective natural prod-ucts means that quantitative data on plant basedessential oils is required. Various publications docu-mented the antibacterial activity of essential oil constit-uents and plant extracts. In recent years, severalresearchers have also reported that the mono- andsesquiterpenoids are the major components of essentialoils which exhibit potential antibacterial activities (Shu-nying et al., 2005).Also, the results of the antibacterial screening showed

that essential oil and various extracts of C. nocturnumhave potential activity against some of the bacterialstrains such as S. aureus (ATCC 6538 and KCTC 1916),L. monocytogenes (ATCC 19166 and ATCC 15313),B. subtilis ATCC 6633, P. aeruginosa KCTC 2004,S. typhimurium KCTC 2515 and E. coli ATCC 8739.This activity could be attributed to the presence ofoxygenated mono- and sesquiterpene hydrocarbons, andthese finding are in agreement with the previous reports(Larsen & Knochel, 1997). C. nocturnum mediated oilalso contained high percentage of phenylethyl alcohol,benzyl alcohol, eicosane, eugenol, n-tetracosane, caryo-

phyllene oxide, 1-hexadecanol, methoxyeugenol andbenzaldehyde, as earlier reported the major componentsof the various essential oils, which have potentialantibacterial properties (El-Sakhawy et al., 1998; Than-gadurai et al., 2002; Deba et al., 2008). Those claimsare further supportedbyourfindings; indicating high con-tents of phenylethyl alcohol, benzyl alcohol, eicosane,eugenol, n-tetracosane, caryophyllene oxide, 1-hexadec-anol, methoxyeugenol and benzaldehyde; comprising65.96% of the oil (Table 1). The antibacterial activity ofindividual component of essential oils such as phenylethylalcohol, benzyl alcohol or eugenol has been reportedpreviously (Lucchini et al., 1990; Jirovetz et al., 2006).On the other hand, the components in lower amount suchas hexadecanoic acid, 1-nonadecanol, heneicosane,methyl anthranilate, nonadecene, nerolidol, tetradecanaland citronellal also contributed to antimicrobial activityof the oil (Jeongmok et al., 1995; El-Sakhawy et al., 1998;Khan et al., 2002; Deba et al., 2008). It is also possiblethat the minor components might be involved in sometype of synergism with the other active compounds(Marino et al., 2001).Also, the results from viable count assay revealed that

exposure of the MIC concentration of the oil had asevere effect on the cell viability of the tested bacteria.L. monocytogenes ATCC19166 and L. monocytogenesATCC15313 were found to be more sensitive to the oil.The oil also exerted its maximum bacterial activityagainst S. aureus ATCC 6538 and P. aeruginosa KCTC2004, as evident by the significant reduction in microbialcounts at 60 min exposure and complete inhibition ofcell viability at 80 min exposure of essential oil.Deans et al. (1995) investigated the susceptibility of

Gram-positive and Gram-negative bacteria to plantvolatile oils and found no evidence for a difference insensitivity between Gram-negative and Gram-positiveorganisms. However, some oils appeared more specific,exerting a greater inhibitory activity against Gram-positive bacteria. It is often reported that Gram-negativebacteria are more resistant to the plant-based essentialoils. The hydrophilic cell wall structure of Gram-negative bacteria is constituted essentially of a lipo-polysaccharide (LPS) that blocks the penetration ofhydrophobic oil and avoids the accumulation of essen-tial oils in target cell membrane (Bezic et al., 2003). Thisis the reason that Gram-positive bacteria were foundto be more sensitive to the essential oil and variousextracts of C. nocturnum than those of Gram-negativebacteria.In this study, we found that essential oil and various

extracts from C. nocturnum growing in Bangladeshinhibited the growth of some representative food-bornepathogenic bacteria. Therefore, essential oils and plantextracts are being considered as potential alternatives tosynthetic bactericides or as leading compounds for newclasses of natural bactericides.

Figure 1 Effect of Cestrum nocturnum L. essential oil (minimum

inhibitory concentration) on viability of the tested bacteria. CT,

control without treatment.



In conclusion, the results of our study suggest thepossibility of using the extract or oil of C. nocturnum asnatural antimicrobials in food industry to control food-borne pathogens. The use of plant extracts and essentialoils in consumer goods is expected to increase in thefuture because of the risk of ‘green consumerism’, whichstimulates the use and development of products derivedfrom plants, as both consumers and regulatory agenciesare more comfortable with the use of natural antimi-crobials. It was found that the essential oils of Salviaofficinalis L. and Schinus molle L. had preservative effectagainst Salmonella inoculated in minced beef meat. Suchfindings would also be confirmed in further studies toestablish the real application of C. nocturnum essentialoil or extracts in foods.

References

Adam, R.P. (2001). Identification of Essential Oil Components by GasChromatography ⁄Quadrupole Mass Spectroscopy. Carol Stream, IL:Allured Publishing Corporation.

Bajpai, V.K., Rahman, A. & Kang, S.C. (2008). Chemical compo-sition and inhibitory parameters of essential oil and extracts ofNandina domestica Thunb. to control food-borne pathogenic andspoilage bacteria. International Journal of Food Microbiology, 125,117–122.

Bakri, I.M. & Douglas, C.W.I. (2005). Inhibitory effect of garlicextract on oral bacteria. Archives of Oral Biology, 50, 645–651.

Bezic, N., Skocibusic, M., Dinkic, V. & Radonic, A. (2003). Compo-sition and antimicrobial activity of Achillea clavennae L. essentialoil. Phytotherapy Research, 17, 1037–1040.

Bouchbaver, G., Jirovetz, L. & Koul, V.K. (1995). Volatiles of theabsolute of Cestrum nocturnum L. Journal of Essential Oil Research,7, 5–9.

Cowan, M.M. (1999). Plant products as antimicrobial agents. ClinicalMicrobiology Reviews, 12, 564–582.

Deans, S.G., Noble, R.C., Hiltunen, R., Wuryani, W. & Penzes, L.G.(1995). Antimicrobial and antioxidant properties of Syzygium arom-aticum (L) Merr Perry: impact upon bacteria, fungi and fatty acidlevels in ageing mice. Flavour and Fragrance Journal, 10, 323–328.

Deba, F., Xuan, T.D., Yasuda, M. & Tawata, S. (2008). Chemicalcomposition and antioxidant, antibacterial and antifungal activitiesof the essential oils from Bidens pilosa Linn. var. Radiata. FoodControl, 19, 346–352.

El-Sakhawy, F.S., El-Tantawy, M.E., Ross, S.A. & El-Sohly, M.A.(1998). Composition and antimicrobial activity of the essential oil ofMurraya exotica L. Flavour and Fragrance Journal, 13, 59–62.

Farber, J.M. (2000). Present situation in Canada regarding Listeriamonocytogenes and ready-to-eat seafood products. InternationalJournal of Food Microbiology, 62, 247–251.

Hao, Y.Y., Brackett, R.E. & Doyle, M.P. (1998). Inhibition of Listeriamonocytogenes and Aeromonas hydrophila by plant extracts inrefrigerated cooked beef. Journal of Food Protection, 61, 307–312.

Jeongmok, K., Marshall, M.R. & Cheng-I, W. (1995). Antibacterialactivity of some essential oil components against five foodborne

pathogens. Journal of Agricultural and Food Chemistry, 43, 2839–2845.

Jirovetz, L., Bail, S., Buchbauer, G. et al. (2006). Antimicrobialtestings, gas chromatographic analysis and olfactory evaluation ofan essential oil of hop cones (Humulus lupulus L.) from Bavaria andsome of its main compounds. Scientia Pharmaceutica, 74, 189–201.

Khan, M., Srivastava, S.K., Syamasundar, K.V., Singh, M. & Naqvi,A.A. (2002). Chemical composition of leaf and flower essential oil ofLantana camara from India. Flavour and Fragrance Journal, 17, 75–77.

Larsen, A.G. & Knochel, S. (1997). Antimicrobial activity of food-related Penicillium sp. against pathogenic bacteria in laboratorymedia and a cheese model system. Journal of Applied Microbiology,83, 111–119.

Lucchini, J.J., Corre, J. & Cremieux, A. (1990). Antibacterial activityof phenolic compounds and aromatic alcohols. Research in Micro-biology, 141, 499–510.

Marino, M., Bersani, C. & Comi, G. (2001). Impedance measurementsto study the antimicrobial activity of essential oils from Lamiaceaceand Compositae. International Journal of Food Microbiology, 67,187–195.

Murray, P.R., Baron, E.J., Pfaller, M.A., Tenover, F.C. & Yolke,R.H. (1995). Manual of Clinical Microbiology. (6th Ed). WashingtonDC, USA: ASM.

Mylotte, J.M., McDermott, C. & Spooner, J.A. (1987). Prospectivestudy of 114 consecutive episodes of Staphylococcus aureus bacteria.Reviews of Infectious Diseases, 9, 891–907.

National Committee for Clinical Laboratory Standard (NCCLS)(2000). Methods for Dilution Antimicrobial Susceptibility Testsfor Bacteria that Grow Aerobically. Approved Standard, M7-A5.New Jersey, USA: National Committee for Clinical LaboratoryStandard.

Ntonifor, N.N., Ngufor, C.A., Kimbi, H.K. & Oben, B.O. (2006).Traditional use of mosquito repellent to protect human againstmosquito and other insect bites in rural community of Cameroon.East African Medical Journal, 83, 553–558.

Nychas, G.J.E., Tassou, C.C. & Skandamis, P. (2003). Antimicrobialsfrom herbs and spices. In: Natural Antimicrobials for the MinimalProcessing of Foods (edited by S.M. Roller). Pp. 176–200. NewYork: CRC Press, Woodhead Publishers.

Pe¢rez-Saad, H. & Buznego, M.T. (2008). Behavioral and antiepilepticeffects of acute administration of the extract of the plant Cestrumnocturnum Lin (lady of the night). Epilepsy & Behavior, 12, 366–372.

Shin, S.Y., Bajpai, V.K., Kim, H.R. & Kang, S.C. (2007). Antibac-terial activity of bioconverted eicosapentaenoic acid (EPA) anddocosahexaenoic acid (DHA) against foodborne pathogenic bacte-ria. International Journal of Food Microbiology, 113, 233–236.

Shunying, Z., Yang, Y., Huaidong, Y., Yue, Y. & Guolin, Z. (2005).Chemical composition and antibacterial activity of the essential oilsof Chrysanthemum indicum. Journal of Ethnopharmacology, 96, 151–158.

Singh, R., Chandra, R., Bose, M. & Luthra, P.M. (2000). Antibacterialactivity of Curcuma longa rhizome extract on pathogenic bacteria.Current Science, 83, 737–740.

Thangadurai, D., Anitha, S., Pullaiah, T., Reddy, P.N. & Ramach-andraiah, O.S. (2002). Essential oil constituents and in vitroantimicrobial activity of Decalepis hamiltonii roots against food-borne pathogens. Journal of Agricultural and Food Chemistry, 50,3147–3149.



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Chemical Composition and Inhibitory Effect of Essential Oil and Organic Extracts of Cestrum Nocturnum L. on Food-borne Pathogens