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Antibacterial activity of essential oils and their active components from Thai spices against foodborne pathogens

October 2013
ScienceAsia 39(5):472

DOI:10.2306/scienceasia1513-1874.2013.39.472

Authors:

Pattamapan Lomarat

Mahidol University

Mullika Chomnawang

Mahidol University

As the popularity of organic food especially fresh vegetables is increasing, it is a common practice to replace chemical fertilizers by manure which leads to high bacterial contamination. Some essential oils such as Thymus vulgaris (thyme) and Ocimum basilicum (basil) oils reduce spoilage flora and foodborne pathogens when used in washing water. This information prompted us to search for effective essential oils from Thai spices for vegetable washing products. Seven out of nine essential oils; fingerroot (Boesenbergia pandurata (Roxb.) Schltr.), galanga (Alpinia galanga (L.) Willd.), holy basil (Ocimum tenuiflorum L.), makrut leaf, makrut peel (Citrus hystrix DC.), sweet basil (O. basilicum L.), and turmeric (Curcuma longa L.) oils showed antibacterial activity. The active components were identified by thin layer chromatography (TLC) bioautography, preparative TLC, and gas chromatography-mass spectrometry. The results indicated that the active components were major components of the oils. The essential oils exhibited higher potency than their active components suggesting that the whole essential oils were more suitable than the pure compounds for product development.

The constituents, minimum inhibitory concentration (MIC), maximum bactericidal concentration (MBC), and active components of essential oils from Thai spices identified by TLC-bioautography and GC-MS.

…

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ESEA RCH ARTI CLE

doi: 10.2306/scienceasia1513-1874.2013.39.472

ScienceAsia 39 (2013): 472–476

Antibacterial activity of essential oils and their active

components from Thai spices against foodborne

pathogens

Phanida Phanthonga, Pattamapan Lomarata, Mullika Traidej Chomnawangb,

Nuntavan Bunyapraphatsaraa,∗

aDepartment of Pharmacognosy, Faculty of Pharmacy, Mahidol University, Sri Ayudhya Road, Rajathevi,

Bangkok 10400 Thailand

bDepartment of Microbiology, Faculty of Pharmacy, Mahidol University, Sri Ayudhya Road,

Rajathevi Bangkok 10400 Thailand

∗Corresponding author, e-mail: nuntavan.bun@mahidol.ac.th

Received 15 Nov 2012

Accepted 25 Jun 2013

ABSTRACT: As the popularity of organic food especially fresh vegetables is increasing, it is a common practice to replace

chemical fertilizers by manure which leads to high bacterial contamination. Some essential oils such as Thymus vulgaris

(thyme) and Ocimum basilicum (basil) oils reduce spoilage ﬂora and foodborne pathogens when used in washing water.

This information prompted us to search for effective essential oils from Thai spices for vegetable washing products. Seven

out of nine essential oils; ﬁngerroot (Boesenbergia pandurata (Roxb.) Schltr.), galanga (Alpinia galanga (L.) Willd.), holy

basil (Ocimum tenuiﬂorum L.), makrut leaf, makrut peel (Citrus hystrix DC.), sweet basil (O. basilicum L.), and turmeric

(Curcuma longa L.) oils showed antibacterial activity. The active components were identiﬁed by thin layer chromatography

(TLC) bioautography, preparative TLC, and gas chromatography-mass spectrometry. The results indicated that the active

components were major components of the oils. The essential oils exhibited higher potency than their active components

suggesting that the whole essential oils were more suitable than the pure compounds for product development.

KEYWORDS: TLC bioautography, GC-MS, active compounds, citral, biological guided separation

INTRODUCTION

Diarrhoea, a disease which causes high morbidity and

mortality, caused at least two million deaths world-

wide in year 2000. Besides, each year 30% of people

in industrialized countries suffer from this foodborne

disease1. The bacteria which are foodborne pathogens

including Escherichia coli,Salmonella Enteritidis,

Salmonella Typhimurium, Salmonella Typhi, Shigella

ﬂexneri,Bacillus cereus, and Staphylococcus aureus,

often contaminate food particularly fresh vegetable2.

At present, the popularity of organic foods, especially

fresh vegetables is increasing and it is a common

practice to use manure instead of chemical fertilizers

which leads to high bacterial contamination. Hence to

control bacterial contamination, an effective and safe

vegetable washing product is needed. Currently, veg-

etable washing products available in the Thai market

are used to remove pesticides, therefore it is necessary

to have the vegetable washing products with antibac-

terial agent in order to decrease the contamination of

the foodborne pathogens.

Some essential oils such as thyme and basil oils

are effective against spoilage ﬂora and foodborne

pathogens when used in washing water3,4. This

information prompted us to search for the active com-

pounds of essential oils from Thai spices. Previous

studies indicated that some essential oils of Thai

spices such as lemongrass, holy basil, turmeric, and

galanga oils had antibacterial properties5–7. However,

an extensive study to identify the active components

has only been done on lemongrass oil, in which citral

was identiﬁed as the active compound5,8.

The aims of this study were to determine the

efﬁcacy of nine commercially available essential oils

of Thai spices as antimicrobial against foodborne

pathogens (E. coli,S. Enteritidis, S. Typhimurium,

S. Typhi, S. ﬂexneri,B. cereus, and S. aureus),

and to identify the active components of each oil.

Biological guided separation was used along with

gas chromatography-mass spectrometry (GC-MS) to

identify active components of the tested oils. Since

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ScienceAsia 39 (2013) 473

the essential oils selected for this study were obtained

from edible plants and were volatile, it is likely that

they will be safe and easy to remove. With proper

research and development, essential oil products may

be an alternative for cleaning fresh vegetables to

eliminate microbial contamination.

MATERIALS AND METHODS

Essential oils

Nine essential oils of Thai spices; black pepper fruit

(Piper nigrum L.), ﬁngerroot rhizome (Boesenbergia

pandurata (Roxb.) Schltr.), galanga rhizome (Alpinia

galanga (L.) Willd.), holy basil leaf (Ocimum tenui-

ﬂorum L.), lemongrass stem (Cymbopogon citratus

Stapf), makrut leaf and peel (Citrus hystrix DC.),

sweet basil leaf (O. basilicum L.), and turmeric rhi-

zome (Curcuma longa L.) oils were obtained from

Thai-China ﬂavour & fragrances industry Co., Ltd.

(Bangkok, Thailand).

Reference compounds

The major compounds of essential oils; (+)-camphor,

(−)-trans-caryophyllene, 1,8-cineole, citral, citronel-

lal, citronellol, eugenol, geraniol, α-humulene, D-lim-

onene, (±)-linalool, methyl chavicol, (−)-α-terpineol,

and terpinen-4-ol were obtained from Sigma-Aldrich

Chemical Co. Inc. (St. Louis, MO). Camphene was

obtained from Carl Roth Co. (Schoemperlenstr, Karl-

sruhe). Methyl cinnamate and methyl eugenol were

obtained from Tokyo Chemical Industry (Tokyo).

Bacterial cultures

Bacterial strains used in this study, E. coli (ATCC

25922), S. Enteritidis (DMST 15676), S. Typhimu-

rium (ATCC 13311), B. cereus (ATCC 11778), S. au-

reus (ATCC 25923), S. ﬂexneri, and S. Typhi were

inoculated and maintained on tryptic soy agar (TSA).

All bacteria were obtained from the Microbiology

Laboratory Culture Collection, Department of Micro-

biology, Faculty of Pharmacy, Mahidol University,

Bangkok, Thailand.

Identiﬁcation of the components in the essential oil

The components of the essential oils were identiﬁed

by GC-MS on GCMS-QP 2010 GC-MS (Shimadzu)

using a DB-5MS bonded phase fused silica capil-

lary column (30 m ×0.25 mm i.d., 0.25 µm ﬁlm

thickness; J&W Scientiﬁc, Folsom, CA). Puriﬁed

helium was used as carrier gas at constant ﬂow rate

of 0.68 ml/min. The oven temperature program for

essential oil was modiﬁed from method of previous

studies9–12. The injector temperature and ion source

temperature were 200 °C and 250 °C, respectively.

Electron impact mass spectra were obtained at 70 eV

by operating in the full scan acquisition mode in

the range of m/z 40–400. The identiﬁcation of the

active compounds were performed by comparing the

obtained mass spectra with those from the Wiley and

NIST spectral library and their retention time and

mass spectral with those of the reference compounds.

Determination of minimum inhibitory

concentration (MIC) and minimum bactericidal

concentration (MBC)

The broth macrodilution method was used to deter-

mine the MICs of oils and reference compounds.

Stock solutions of oils were initially dissolved in

tween 80 and 95% ethanol then a series of two-

fold dilutions of each oil (ranging 200 µg/ml to

1.5625 µg/ml) was prepared in tryptic soy broth

(TSB). Freshly grown bacterial suspensions in TSB

were adjusted to approximately 106CFU/ml. For MIC

determination, a set of 10 assay tubes in duplicate was

employed per sample. The ﬁrst test tube contained

1.8 ml of the seeded broth and the remaining tubes

had 1 ml each. The solution of the test agent (0.2 ml)

was added to the ﬁrst tube to bring the volume to

2 ml. One ml of this was transferred to the next tube

and the process was repeated giving a two-fold serial

dilution. The tubes were incubated at 37 °C for 24 h.

The ﬁrst assay tube with no apparent growth of the

microorganism containing the lowest dilution of the

test essential oil represented the MIC. The bactericidal

effect was assessed by MBC determination. Samples

were removed from tubes that showed no turbidity

and were dropped onto TSA plate. After incubation

at 37 °C for 24 h the minimum concentration without

visible growth was reported as MBC13 .

Determination of the active components by thin

layer chromatography (TLC) bioautography

The TLC bioautographic method was used to detect

the active components. After application of oils and

reference standards on three silica gel G60 F254 alu-

minium plates (A, B, C), the plates were developed us-

ing toluene-ethyl acetate (93:7) as the solvent. Plate A

was visualized under UV light at 254 nm and sprayed

with anisaldehyde sulphuric acid. Then, it was heated

at 110 °C for 5 min to detect the separated components

and used as reference chromatogram. Plate B was

prepared for the isolation of active compounds of

essential oil.

The TLC bioautography method was modiﬁed

from the method of Chomnawang et al14 . The TLC

plate (C) was developed as described above. The

TLC plate (C) was placed on the top of agar base

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474 ScienceAsia 39 (2013)

and inocula of bacterial strains in TSA media (agar

seed) was distributed over TLC plate (C). The plate

compounds were identiﬁed by the spots within the

inhibition zones. Rf of the corresponding spots were

compared with Rf of reference standard on plate A.

Plate B was compared with plates A and C. The areas

on the TLC plate which corresponded to the inhibition

zones were scraped from the plate and the substances

were eluted from the adsorbent with hexane. Eluted

samples were ﬁltered with ﬁlter paper (Whatman

No 1), concentrated by removing the solvent under

vacuum. Then, the active components were conﬁrmed

by gas chromatography-mass spectrometry (GC-MS).

RESULTS AND DISCUSSION

GC analysis of the components of the essential

oils from Thai spices revealed that the major com-

ponents of black pepper, ﬁngerroot, galanga, holy

basil, lemongrass, makrut leaf and peel, sweet basil,

and turmeric oils, were δ-3-carene, trans-β-ocimene,

1,8-cineole, eugenol, E-citral, β-citronellal, limonene,

methyl chavicol, and ar-tumerone, respectively

(Table 1). The antibacterial testing against foodborne

pathogens showed that seven essential oils of Thai

spices exhibited the activity with MIC lower than

125 µg/ml (Table 1). In this study, the cut off limit was

set up as recommended by UNIDO for commercially

potential agents, which were 125 µg/ml and 10 µg/ml

for crude extract and pure compound13, respectively.

Since lemongrass oil has been well known to contain

citral as active component, it was used as a positive

control in this study. As a result of the activity

against the tested bacteria, none of the tested oils

were comparable to lemongrass oil. However, among

seven essential oils, holy basil and sweet basil oils

showed the widest spectrum (6 strains) followed by

makrut leaf and ﬁngerroot oils (4 strains), galanga,

makrut peel, and turmeric oils (1 strain), in that order

(Table 1). The holy basil, makrut leaf, and sweet

basil oils also showed the highest potency (25 µg/ml).

The results suggest that besides lemongrass oil, sweet

basil oil showed the highest potential for commercial

products followed by holy basil and makrut leaf oils.

Some of our results were in agreement with previous

reports6,7.

Preliminary identiﬁcation by TLC autobiography

found positive bands on TLC chromatogram of each

oil (Table 1). However, the identiﬁcation by TLC

was limited. The large amount of the oil required to

produce antibacterial activity resulted in overlapping

of the adjacent components and prevented a precise

identiﬁcation. Hence the identiﬁcation was conﬁrmed

by GC-MS. Most of the active components were

found to be the major constituents of essential oils.

The major active components of ﬁngerroot, galanga,

holy basil, makrut leaf, makrut peel, sweet basil, and

turmeric oils were 1,8-cineole/camphor, 1,8-cineole,

eugenol, citronellal, terpinen-4-ol/α-terpineol, methyl

chavicol, and ar-tumerone, respectively. All other

active components are shown in Table 1. The at-

tempt to isolate active components by preparative

TLC was not successful due to the instability of each

component. Hence all the commercially available

active compounds were used and subjected to an-

tibacterial testing and all of the compounds showed

the MICs over 50 µg/ml which is over the cut-off

limit recommended by UNIDO13. Thus the oils are

recommended for product development rather than the

active components.

Some of the antibacterial components found

in Thai spices were reported to be active including

trans-α-bergamotene, camphor, trans-caryophyllene,

1,8-cineole, citronellal, eugenol, α-humulene,

(±)-linalool, methyl eugenol, methyl chavicol, neral,

α-terpineol, and terpinen-4-ol 15–21 . In this study,

new active components against foodborne pathogen,

citronellol, ar-curcumene, β-farnesene, cis-farnesol,

trans-farnesol, and turmerone, were found. None of

these active compounds showed a potency comparable

to that of citral (5 µg/ml). They exhibited the activity

with MICs over the UNIDO cut off limit (10 µg/ml)13 .

Based on the results, the oils were more appropriate

than active components for product development.

The potential role of essential oil as food preser-

vatives has been recognized but the concentration nec-

essary to inhibit foodborne pathogens is high which

leads to the undesirable organoleptic effect22 . Only

few articles reported on the use of essential oil in

the washing solution for decontamination of fresh

vegetable3,4,15 . Based on the antibacterial activity

and the ﬂavour of the essential oils, lemongrass, sweet

basil, holy basil, and makrut leaf oils were suggested

to be used in washing solution for fresh vegetables.

In this study, sweet basil oil contained methyl

chavicol (estragol) as active components against

S. ﬂexneri,S. Typhi, and S. aureus which was in agree-

ment with previous study15. Methyl chavicol has been

reported to exhibit weaker activity against Shigella

spp. than carvacrol and thymol which is probably

due to the substitution of phenolic hydroxyl group

with methyl group15. However, Thai sweet basil oil

which contained 90% methyl chavicol showed the

inhibitory activity against E. coli with the MIC of

25 µg/ml. Hence it was considered to be potential for

the vegetable washing products.

www.scienceasia.org

ScienceAsia 39 (2013) 475

Table 1 The constituents, minimum inhibitory concentration (MIC), maximum bactericidal concentration (MBC), and

active components of essential oils from Thai spices identiﬁed by TLC-bioautography and GC-MS.

Essential oil Constituents MIC MBC Bacterial Active Identiﬁcation by TLC and GC-MS

(µg/ml) (µg/ml) strainsaband

Black pepper δ-3-carene (37%), >200 >200 All 7 bacteria ND ND

limonene (32%),

β-pinene (17%),

caryophyllene (8%)

Fingerroot trans-β-ocimene (27%), 100 200 B. cereus 3 geraniol, α-terpineol, 1,8-cineole, camphor,

camphor (24%), neral, and unidentiﬁedb

1,8-cineole (17%), 100 100 S. Typhi 5 geraniol, α-terpineol, (±)-linalool,

geraniol (11%), 1,8-cineole, camphor, neral, and unidentiﬁedb

camphene (8%), 100 >200 S. ﬂexneri 3 geraniol, α-terpineol, (±)-linalool, and unidentiﬁedb

cis-ocimene (3%), 100 >200 E. coli 2 geraniol, α-terpineol, and unidentiﬁedb

methyl-cis-cinnamate (3%)

Galanga 1,8-cineole (34%) 50 50 B. cereus 6 1,8-cineole,tau-muurolol, and unidentiﬁedb

β-farnesene (15%),

trans-caryophyllene (12%),

zingiberene (4%)

Holy basil eugenol (42%), 25 50 B. cereus 2 eugenol, methyl eugenol, and unidentiﬁedb

caryophyllene (26%), 50 >200 S. aureus 3 eugenol, methyl eugenol, and unidentiﬁedb

methyl eugenol (15%), 50 100 S. Typhi 1 eugenol, methyl eugenol

(−)-β-elememe (12%) 100 >200 S. Typhimurium 2 eugenol, methyl eugenol, and unidentiﬁedb

100 200 S. ﬂexneri 2 eugenol, methyl eugenol, and unidentiﬁedb

100 200 E. coli 2 eugenol, methyl eugenol, and unidentiﬁedb

Makrut leaf β-citronellal (78%), 25 25 B. cereus 5 citronellol, cis-farnesol, trans-farnesol, citronellal,

citronellyl acetate (6%), and unidentiﬁedb

β-citronellol (5%) 50 50 S. Typhi 4 citronellol, cis-farnesol, citronellal, and unidentiﬁedb

50 >200 S. Typhimurium 1 unidentiﬁedb

50 >200 S. ﬂexneri 5 citronellol, cis-farnesol, citronellal, and unidentiﬁedb

Makrut peel limonene (46%), 100 100 S. Typhi 3 α-terpineol, terpinen-4-ol, and unidentiﬁedb

α-terpineol (19%),

β-pinene (18%),

terpinen-4-ol (17%)

Sweet basil methyl chavicol (90%), 50 100 B. cereus 2 2 unidentiﬁedb

α-bergamotene (3%) 100 >200 S. aureus 4 methyl chavicol and 3 unidentiﬁedb

50 50 S. Typhi 3 methyl chavicol and 2 unidentiﬁedb

50 >200 S. Typhimurium 1 unidentiﬁedb

25 50 S. ﬂexneri 3 methyl chavicol and 2 unidentiﬁedb

25 50 E. coli 2 2 unidentiﬁedb

Turmeric Ar-tumerone (45%), 50 >200 S. Typhi 2 tumerone, Ar-curcumene, and trans-caryophyllene

curlone (14%),

tumerone (12%),

α-curcumene (7%),

β-sesquiphellandrene (6%)

Lemongrass E-citral (53%), 25 25 S. aureus 1 citral

Z-citral (38%), 12.5 12.5 B. cereus 1 citral

geraniol (4%) 100 100 S. Typhi 1 citral

*Positive control 100 100 S. Typhimurium 1 citral

50 50 S. ﬂexneri 1 citral

100 100 S. Enteritidis 1 citral

50 50 E. coli 1 citral

aThe bacterial strains not present in this table exhibited MIC and MBC of oils higher than 200 µg/ml.

bLack of reference compound.

ND: Not determined.

Holy basil, one of the active oils contained

eugenol (42%) and methyl eugenol (15%) which was

found to be active against S. Typhimurium, S. Ty-

phi, S. ﬂexneri,E. coli,S. aureus, and B. cereus.

The results from this study supported previous report

which indicated that eugenol was active. Eugenol

exerted the activity not only at the membrane but also

inhibited the production of amylase and protease by

organisms21,23. However, the unpleasant ﬂavour of

eugenol may not be accepted by consumers. Another

potential oil, makrut leaf oil contained different active

compounds. The major active components were cit-

ronellal (78%) and citronellol (5%). The activities of

citronellal and citronellol were due to aldehyde and

alcohol functional groups, respectively22 .

CONCLUSIONS

In conclusion, four essential oils of Thai spices,

lemongrass, holy basil, makrut leaf, and sweet basil

oils showed the inhibitory activity against foodborne

pathogens with the MICs 25–100 µg/ml. The major

active components were identiﬁed along with other

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476 ScienceAsia 39 (2013)

components using TLC-bioautography and GC-MS

techniques. Since most of the components are less

active than the whole oils, it is recommended to

use the whole oil for vegetable washing solution.

This study also identiﬁed the new antibacterial agents

against foodborne pathogens including citronellol, ar-

curcumene, and turmerone.

Acknowledgements:The authors are grateful to the Co-

ordinating Centre for Research and Development to increase

value of the Plants Indigenous to Thailand, Mahidol Univer-

sity and the Thailand Research Fund for ﬁnancial support.

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Sep 2022
CRIT REV BIOTECHNOL

Food commodities are often contaminated by microbial pathogens in transit or during storage. Hence, mitigation of these pathogens is necessary to ensure the safety of food commodities. Globally, researchers used botanicals as natural additives to preserve food commodities from bio-deterioration, and advances were made to meet users' acceptance in this domain, as synthetic preservatives are associated with harmful effects to both consumers and environments. Over the last century, the genus Curcuma has been used in traditional medicine, and its crude and nanoencapsulated essential oils (EOs) and curcuminoids were used to combat harmful pathogens that deteriorate stored foods. Today, more research is needed for solving the problem of pathogen resistance in food commodities and to meet consumer demands. Therefore, Curcuma-based botanicals may provide a source of natural preservatives for food commodities that satisfy the needs both of the food industry and the consumers. Hence, this article discusses the antimicrobial and antioxidant properties of EOs and curcuminoids derived from the genus Curcuma. Further, the action modes of Curcuma-based botanicals are explained, and the latest advances in nanoencapsulation of these compounds in food systems are discussed alongside knowledge gaps and safety assessment where the focus of future research should be placed.

GC-MS Analysis and Study of the Antimicrobial Activity of Citrus paradisi, Citrus aurantifolia, and Citrus sinensis Peel Essential Oils as Hand Sanitizer

Article

Full-text available

Jan 2024

In the setting of healthcare, the use of hand sanitizers and antiseptics for hand hygiene is of paramount importance to avoid transfer of pathogenic microorganism through hand and skin contact. There is an increasing interest in the incorporation of essential oils in hand sanitizer’s formula to avoid the adverse effect of conventional hand sanitizers on health. This study aimed to detect the chemical constituents of citrus peel essential oils and study their antimicrobial activity compared with commercial hand sanitizers. The qualitative and quantitative analysis of the hydrodistillated essential oils of peels of grapefruit (Citrus paradisi), lime (Citrus aurantifolia), and orange (Citrus sinensis) were carried out using gas chromatography mass spectroscopy. The disc diffusion method was used to screen the antibacterial activity of the essential oils against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, and Candida albicans compared with a 78% alcohol-based commercial hand sanitizer. The antimicrobial testing results were statistically analyzed. The highest yield percentage of the obtained essential oils was 1.09% obtained by orange oil. The GC-MS analysis indicated that monoterpene and sesquiterpene hydrocarbons occupied the largest portion of the chemical composition of the three essential oils with D-limonene as the most predominant component. All essential oils showed activity against all tested organisms. Lime essential oil showed comparable antimicrobial activity relative to the commercial 78% alcohol hand sanitizer. In conclusion, essential oils obtained from citrus fruit peel represent a rich source of compounds possessing antimicrobial properties and could be an alternative to synthetic antimicrobial agents.

Antibacterial activity of curcumin and its essential nanoformulations against some clinically important bacterial pathogens: A comprehensive review

Article

Full-text available

Nov 2021

Multidrug resistant bacterial infections can kill 700,000 individuals globally each year and is considered among the top ten global health threats faced by humanity as the arsenal of antibiotics is becoming dry and alternate antibacterial molecule is in demand. Nanoparticles of curcumin exhibit appreciable broad spectrum antibacterial activity using unique and novel mechanisms and thus the process deserves to be reviewed and further researched to clearly understand the mechanisms. Based on the antibiotic resistance, infection and virulence potential, a list of clinically important bacteria was prepared after extensive literature survey and all recent reports on the antibacterial activity of curcumin and its nanoformulations as well as their mechanism of antibacterial action have been reviewed. Curcumin, nanocurcumin and its nanocomposites with improved aqueous solubility and bioavailability are very potential, reliable, safe and sustainable antibacterial molecule against clinically important bacterial species that uses multi‐target mechanism such as inactivation of antioxidant enzyme, ROS mediated cellular damage and inhibition of acyl‐homoserine‐lactone synthase (AHL‐synthase) necessary for quorum sensing and biofilm formation thereby bypassing the mechanisms of bacterial antibiotic resistance. Nanoformulations of curcumin can thus be considered as a potential and sustainable antibacterial drug candidate to address the issue of antibiotic resistance. This article is protected by copyright. All rights reserved

Optimization studies and compositional analysis of subcritical water extraction of essential oil from Citrus hystrix DC. leaves

Article

Aug 2021
J SUPERCRIT FLUID

Subcritical water extraction (SWE) of essential oil (EO) from Citrus hystrix DC. leaves was optimized using response surface methodology (RSM), involving factors of particle size (0.5-1) mm, sample-to-solvent ratio (0.025-0.175) g/mL, extraction temperature (140-180) ºC, and extraction time (20-40) minutes. Thus, an optimal EO yield of (2.14 ± 0.03) % (w/w) was obtained at 0.75 mm, 0.025 g/mL, 174 ºC, and 29 minutes. SWE was found to yield significantly higher EO than the conventional hydrodistillation, within a shorter time. The regression model was established, presenting a significant quadratic correlation (R² = 0.97) and adequate for predictions. SWE at 160 ºC and 180 ºC yielded 36 compounds, with isopulegol-dominant, exceeding SWE at 140 ºC (21 compounds) and hydrodistillation (25 compounds). SWE with tunable temperatures not only improved the quantity of EO but was also capable of enhancing the quality because more EO compounds were extracted, offering diverse functionalities to nutraceutical sectors.

Antibacterial phenolic compounds from the flowering plants of Asia and the Pacific: coming to the light

Article

Full-text available

Oct 2024

Context The emergence of pan-resistant bacteria requires the development of new antibiotics and antibiotic potentiators. Objective This review identifies antibacterial phenolic compounds that have been identified in Asian and Pacific Angiosperms from 1945 to 2023 and analyzes their strengths and spectra of activity, distributions, molecular masses, solubilities, modes of action, structures-activities, as well as their synergistic effects with antibiotics, toxicities, and clinical potential. Methods All data in this review was compiled from Google Scholar, PubMed, Science Direct, Web of Science, and library search; other sources were excluded. We used the following combination of keywords: ‘Phenolic compound’, ‘Plants’, and ‘Antibacterial’. This produced 736 results. Each result was examined and articles that did not contain information relevant to the topic or coming from non-peer-reviewed journals were excluded. Each of the remaining 467 selected articles was read critically for the information that it contained. Results Out of ∼350 antibacterial phenolic compounds identified, 44 were very strongly active, mainly targeting the cytoplasmic membrane of Gram-positive bacteria, and with a molecular mass between 200 and 400 g/mol. 2-Methoxy-7-methyljuglone, [6]-gingerol, anacardic acid, baicalin, vitexin, and malabaricone A and B have the potential to be developed as antibacterial leads. Conclusions Angiosperms from Asia and the Pacific provide a rich source of natural products with the potential to be developed as leads for treating bacterial infections.

Antibacterial Efficacy of Essential Oils from Four Spices against Salmonella typhimurium: Mathematical Modelling and Application in Enhancing Salad Cream Safety

Article

Full-text available

Dec 2023

The study was conducted to investigate the inhibitory effects of certain natural substances (finger root, clove, lemongrass, cardamom, and the combination of lemongrass with cardamom) against Salmonella typhimurium, a type of bacteria known to cause foodborne illnesses. The result showed that finger root, clove, lemongrass, cardamom, and the combination of lemongrass with cardamom exhibited strong inhibitory effects against S. typhimurium. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were evaluated. MIC values ranged from 0.049 to 0.781 µl/ml, and MBC values ranged from 0.049 to 6.250 µl/ml. Furthermore, the study aimed to develop mathematical models that accurately describe S. typhimurium survival in the presence of these essential oils. By understanding how the S. typhimurium respond to the oils over time, it was found that the mathematical models accurately described bacterial survival, with the modified Gompertz model fitting for finger root essential oil and the Weibull and modified Gompertz models suitable for the other oils. Additionally, the study sought to evaluate the practical viability of incorporating these essential oils into salad cream formulations, primarily aiming to assess their potential in reducing S. typhimurium counts and ensuring compliance with established quality standards. Specifically, the inclusion of finger root, clove, lemongrass, cardamom, and the combination of lemongrass with cardamom in salad cream formulations, maintained at a controlled temperature of 4 °C, yielded positive outcomes, meeting the required quality standards. Importantly, the presence of S. typhimurium was rendered undetectable, and an overall reduction in microbial count was observed when compared to cream formulations lacking these essential oils. This study effectively underscores the potential of the examined essential oils as natural antimicrobial agents suitable for incorporation in food products

Chemical composition, antioxidant, and antimicrobial activities of Bangladesh-origin Jhum-cultivar basil (Ocimum basilicum L.) essential oil.

Article

Full-text available

Aug 2023

Essential oil (EO) from the sweet basil (Ocimum basilicum L.) grown in the Jhum cultivations located in Bangladesh was screened for chemical composition, antioxidant, and antimicrobial activities. EO yield from the Jhum-cultivar O. basilicum was 1.55% (v/w). Analysis of EO indicated the presence of several bioactive compounds, among which Geranial (35.5%) and cis-citral (26.2%) are of significant content. The EO showed antioxidant activities inhibiting DPPH radical with a mean value of 45.7% at 2.4 mg mL–1 of EO. The EO has susceptibility against Gram-positive and Gram-negative bacteria (Escherichia coli, Salmonella Typhi, Vibrio cholerae, Staphylococcus aureus, Bacillus cereus, and Micrococcus spp.), with a notable activity against the Gram-positive bacteria.

Ocimum Species: A Review on Chemical Constituents and Antibacterial Activity

Article

Full-text available

Sep 2022
MOLECULES

Infection by bacteria is one of the main problems in health. The use of commercial antibiotics is still one of the treatments to overcome these problems. However, high levels of consumption lead to antibiotic resistance. Several types of antibiotics have been reported to experience resistance. One solution that can be given is the use of natural antibacterial products. There have been many studies reporting the potential antibacterial activity of the Ocimum plant. Ocimum is known to be one of the medicinal plants that have been used traditionally by local people. This plant contains components of secondary metabolites such as phenolics, flavonoids, steroids, terpenoids, and alkaloids. Therefore, in this paper, we will discuss five types of Ocimum species, namely O. americanum, O. basilicum, O. gratissimum, O. campechianum, and O. sanctum. The five species are known to contain many chemical constituents and have good antibacterial activity against several pathogenic bacteria.

Journey of Alpinia galanga from kitchen spice to nutraceutical to folk medicine to nanomedicine

Article

Feb 2022
J ETHNOPHARMACOL

Ethanopharmacological importance Alpinia galanga (L.) Willd, belonging to Zingiberaceae family is used as a spice and condiment in various culinary preparations of Indonesia, Thailand and Malaysia.It has been also used as a key ingredient in various traditional systems of medicine for the treatment of throat infection, asthma, urinary ailments, inflammation and rheumatism amongst other conditions. A. galanga (AG) is widely used as a functional food and included in various preparations to obtain its nutraceutical and pharmacological benefits of its phytoconstituents such as phenyl propanoids, flavonoids and terpenoids. Over the past decades, several researchers have carried out systematic investigation on various parts of AG. Numerous studies on AG rhizomes have shown positive pharmacological effects such as anti-inflammatory, anticancer, antipsoriasis, antiallergic, neuroprotective and thermogenesis. Till date, no comprehensive review summarizing the exploitation of AG into nanomedicine has been published. Aim of the review This comprehensive review aims to briefly discuss cultivation methods, propagation techniques, extraction processes for AG. The ethnopharmacological uses and pharmacological activities of AG extracts and its isolates are discussed in detail which may contribute well in further development of novel drug delivery system (NDDS) i.e. future nanomedicine. Materials and methods Information about AG was collected using search engine tools such as Google, Google Scholar, PubMed, Google Patent, Web of Science and bibliographic databases of previously published peer-reviewed review articles and research works were explored. The obtained data sets were sequentially arranged for better understanding of AG's potential. Results More advanced genetic engineering techniques have been utilized in cultivation and propagation of AG for obtaining better yield. Extraction, isolation and characterization techniques have reported numerous phytoconstituents which are chemically phenolic compounds (phenyl propanoids, flavonoids, chalcones, lignans) and terpenes. Ethnopharmacological uses and pharmacological activity of AG are explored in numerous ailments, their mechanism of action and its further potential to explore into novel drug delivery system are also highlighted. Conclusions The review highlights the importance of plant tissue culture in increasing the production of AG plantlets and rhizomes. It was understood from the review that AG and its phytoconstituents possess numerous pharmacological activities and have been explored for the treatment of cancer, microbial infection, gastrointestinal disorders, neuroprotective effects, obesity and skin disorders. However, the use of AG as alternative medicine is limited owing to poor solubility of its bioactive components and their instability. To overcome these challenges, NDDS have been utilized and found good success in overcoming its aforementioned challenges. Furthermore, efforts are required towards development of scalable, non-toxic and stable NDDS of AG and/or its bioactives.

Eugenol induced inhibition of extracellular enzyme production by Bacillus cereus

Article

Full-text available

Jun 1989
J FOOD PROTECT

Eugenol, the major essential oil of clove, in sublethal concentrations (0.02–0.03%, v/v) inhibited the production of alpha-amylase, protease, and subtilisin by Bacillus subtilis in laboratory media. Microscopic observations revealed that at these eugenol concentrations, B. subtilis cells appeared swollen and distorted and/or appeared as very long and thin filaments (> 100 μm). Of 20 amino acids investigated, only L-glutamic or L-aspartic acid (>5.0 mg/ml) prevented such morphogenic distortions when added to eugenol-containing media before inoculation. Addition of these amino acids also resulted in an increase in biomass and protease production. In contrast, the addition of serine (> 1.0 mg/ml) enhanced filamentous growth but reduced the production of protease and subtilisin.

Chemical Composition, Antioxidant and Antimicrobial Activities of Basil (Ocimum basilicum) Essential oils Depends on Seasonal Variations

Article

Jun 2008
FOOD CHEM

Chemical composition, antioxidant and antimicrobial activities of the essential oils from aerial parts of basil (Ocimum basilicum L.) as affected by four seasonal, namely summer, autumn, winter and spring growing variation were investigated. The hydro-distilled essential oils content ranged from 0.5% to 0.8%, the maximum amounts were observed in winter while minimum in summer. The essential oils consisted of linalool as the most abundant component (56.7-60.6%), followed by epi-α-cadinol (8.6-11.4%), α-bergamotene (7.4-9.2%) and γ-cadinene (3.2-5.4%). Samples collected in winter were found to be richer in oxygenated monoterpenes (68.9%), while those of summer were higher in sesquiterpene hydrocarbons (24.3%). The contents of most of the chemical constituents varied significantly (p<0.05) with different seasons. The essential oils investigated, exhibited good antioxidant activity as measurements by DPPH free radical-scavenging ability, bleaching β-carotene in linoleic acid system and inhibition of linoleic acid oxidation. Evaluation of antimicrobial activity of the essential oils and linalool, the most abundant component, against bacterial strains: Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pasteurella multocida and pathogenic fungi Aspergillus niger, Mucor mucedo, Fusarium solani, Botryodiplodia theobromae, Rhizopus solani was assessed by disc diffusion method and measurement of determination of minimum inhibitory concentration. The results of antimicrobial assays indicated that all the tested microorganisms were affected. Both the antioxidant and antimicrobial activities of the oils varied significantly (p<0.05), as seasons changed. Copyright © 2007 Elsevier Ltd. All rights reserved.

The effect of autoxidation of lemon‐grass oil on its antibacterial activity

Article

May 1993
PHYTOTHER RES

Lara (Omolara) Olajumoke Orafidiya

The effect of autoxidation of lemon-grass oil on its antibacterial activity has been studied. Using the Active Oxygen method, the oil was found to undergo rapid oxidation under accelerated test conditions. The oxidized oil samples were found to have reduced activity against bacteria. This activity was completely lost in extensively oxidized oil samples. Inclusion of antioxidants in the oil samples reduced the rate of oxidation and enhanced the antibacterial activity of the oil. The effects of the antioxidants were concentration dependent, and at their effective concentrations, oxidation was completely prevented for the period of the test.

Gas chromatography-mass spectrometry coupled with pseudo-Sadtler retention indices, for the identification of components in the essential oil of Curcuma longa L.

Article

Jan 1997
J CHROMATOGR A

Gas chromatography-mass spectrometry was applied to the cyclohexane extract of Curcuma longa L. The chromatographic conditions generated retention indices very close i.e., greater than 99.9%, to those reported for structures in the Sadtler Standard Gas Chromatography Retention Index Library. In addition to the extensively reported sesquiterpene ketones, this essential oil extract contained a series of saturated and unsaturated fatty acids. Wiley mass spectra library matching for the free fatty acids, their trimethylsilyl esters and methyl esters narrowed their identity down to a few candidates. Combining this information with the retention indices of the fatty acid methyl esters in the Sadtler library allowed the identification of some of the double bond positions.

Efficacy of Chlorine Dioxide, Ozone, and Thyme Essential Oil or a Sequential Washing in Killing Escherichia coli O157:H7 on Lettuce and Baby Carrots

Article

Dec 2002
LWT-FOOD SCI TECHNOL

Chlorine dioxide (ClO2), ozone, and thyme essential oil has been found to be effective in reducing pathogens, including Escherichia coli O157:H7, on selected produce. The efficacy of these sanitizers was evaluated, alone or through their sequential washing to achieve a 3 or more log reduction of mixed strains of E. coli O157:H7 on shredded lettuce and baby carrots. Samples sprinkle inoculated with mixed strains of E. coli O157:H7 were air-dried for 1 h at 22±2°C in a biosafety cabinet, stored at 4°C for 24 h, and then treated with different concentrations of disinfectants and exposure time. Sterile deionized water washing resulted in approximately 1log reduction ofE. coli O157:H7 after 10 min washing of lettuce and baby carrots. Gaseous treatments resulted in higher log reductions in comparison to aqueous washing. However, decolorization of lettuce leaves was observed during long exposure time. A logarithmic reduction of 1.48–1.97log10 cfu/g was obtained using aqueous ClO2 (10.0 mg/L for 10 min) ozonated water (9.7 mg/L for 10 min) or thyme oil suspension (1.0 mL/L for 5 min) on lettuce and baby carrots. Of the three sequential washing treatments used in this study, thyme oil followed by aqueous ClO2/ozonated water, or ozonated water/aqueous ClO2 were significantly (P<0.05) more effective in reducing E. coli O157:H7 (3.75 and 3.99log, and 3.83 and 4.34 log reduction) on lettuce and baby carrots, respectively. The results obtained from this study indicate that sequential washing treatments could achieve 3–4log reduction of E. coli O157:H7 on shredded lettuce and baby carrots.

Inhibitory effect of thyme and basil essential oils, carvacrol, thymol, estragol, linalool and p-cymene towards Shigella sonnei and S. Flexneri

Article

Feb 2004

There are a few reports on the antimicrobial activity of essential oils or their major constituents towards Shigella sp. The antimicrobial effect of basil and thyme essential oil and its major constituents thymol, p-cymene, estragol, linalool, and carvacrol was determined using the agar well diffusion assay. Thyme essential oil and thymol and carvacrol showed inhibition of Shigella sp. in the agar well diffusion method. The potential of thyme essential oil, thymol and carvacrol at 0.5% and 1.0% v/v for decontamination of lettuce was evaluated. A decrease of the shigellae was observed after washing with 0.5% while at 1% Shigella numbers dropped below the detection limit. However, the antimicrobial effect on a subsequent lettuce sample in the same decontamination solution was significantly decreased. In addition, application of thyme essential oil or thymol or carvacrol for decontamination is hampered by sensoric properties of the lettuce (browning, strong odour).

Antifungal activity of some essential oil components

Article

Oct 1986

Fifteen essential oil components were evaluated for antifungal activity towards five spoilage-causing fungi. In liquid shake cultures, unsaturated aldehydes (citral, cinnamic aldehyde and cittronellal) followed by geraniol, an unsaturated alcohol were most inhibitory to Aspergillus niger, Fusarium oxysporum and Penicillium digitatum; their minimal inhibitory concentrations (MIC) was 100 μg ml−1. Menthol, a terpene alcohol was most inhibitory to Rhizopus stolonifer and Mucor sp. with a MIC of 200 μg ml−1. Hydrocarbons like camphene, limonene and α-terpinene were least inhibitory. When incorporated in agar medium different patterns of activity were found. Thus citral, cinnamic aldehyde, citronellal, geraniol and menthol not only failed to completely inhibit A. niger, F. oxysporum and P. digitatum but were more active against R. stolonifer and Mucor sp. than in liquid medium. The differences were due to the vapour of the volatile test compounds which accumulated over the agar medium. The growth inhibition due to the vapours alone was measured by using structurally modified petri-plates. The vapours were more active against R. stolonifer and Mucor sp. than against A. niger, F. Oxysporum and P. digitatum. Fungal growth inhibition by volatile compounds in agar medium reflects the combined activity of the vapour and the compound incorporated in the medium and the inhibition is different from that obtained in liquid medium. Regarding the structure-activity relationship of citral, the-CHO group in conjugation with a carbon to carbon double bond (CC) was found to be responsible for the antifungal activity of the molecule.

Antibacterial activity of some essential oil components against five foodborne pathogens

Article

Nov 1995

Antibacterial activity of 11 essential oil constituents against Escherichia coli, E. coli O157:H7, Salmonella typhimurium, Listeria monocytogenes, and Vibrio vulnificus was tested at 5, 10, 15, and 20% in 1% Tween 20 using a paper disk method. Eight constituents were then tested in liquid medium to determine minimum inhibitory and minimum bactericidal concentrations (MIC and MBC, respectively). V. vulnificus was most susceptible using disk assay. Carvacrol showed strong bactericidal activity against all tester strains, while limonene, nerolidol, and β-ionone were mostly inactive. Carvacrol was highly bactericidal against S. typhimurium and V. vulnificus in liquid medium (MBC 250 μg/mL). Citral and perillaldehyde had MBCs of 100 and 250 μg/mL against V. vulnificus. Terpineol and linalool were least potent against tester strains, with MBCs of 1000 μg/ mL. Citral, geraniol, and perillaldehyde at 500 μg/mL completely killed E. coli, E. coli O157:H7, and S. typhimurium, while citronellal at 250 μg/mL killed V. vulnificus. Therefore, these compounds could serve as potential antibacterial agents to inhibit pathogen growth in food.

Eugenol (an essential oil of clove) acts as an antibacterial agent against Salmonella typhi by disrupting the cellular membrane

Article

May 2010

To evaluate the antibacterial activity of eugenol and its mechanism of bactericidal action against Salmonella typhi. The antibacterial activity was checked by disc-diffusion method, MIC, MBC, time course assay and pH sensitivity assay. The chemo-attractant property of eugenol was verified by chemotaxis assay. The mode of action of eugenol was determined by crystal violet assay, measurement of release of 260 nm absorbing material, SDS-PAGE, FT-IR spectroscopy, AFM and SEM. Treatment with eugenol at their MIC (0.0125%) and MBC (0.025%) reduced the viability and resulted in complete inhibition of the organism. Eugenol inactivated Salmonella typhi within 60 min exposure. The chemo-attractant property of eugenol combined with the observed high antibacterial activity at alkaline pH favors the fact that the compound can work more efficiently when given in vivo. Eugenol increased the permeability of the membrane, as evidenced by crystal violet assay. The measurement of release of 260 nm absorbing intracellular materials, SDS-PAGE, SEM and AFM analysis confirmed the disruptive action of eugenol on cytoplasmic membrane. The deformation of macromolecules in the membrane, upon treatment with eugenol was verified by FT-IR spectroscopy. The results suggest that the antibacterial activity of eugenol against Salmonella typhi is due to the interaction of eugenol on bacterial cell membrane.

Topley & Wilson's Principles of Bacteriology and Immunity

Article