J Food Sci Technol (November 2017) 54(12):3948–3958
DOI 10.1007/s13197-017-2859-2
ORIGINAL ARTICLE
In-vitro antimicrobial activity and identification of bioactive
components using GC–MS of commercially available essential oils
in Saudi Arabia
Syed Amir Ashraf1 • Eyad Al-Shammari1 • Talib Hussain2 • Shaikh Tajuddin3
Bibhu Prasad Panda3
•
Revised: 1 July 2017 / Accepted: 7 September 2017 / Published online: 21 September 2017
Ó Association of Food Scientists & Technologists (India) 2017
Abstract This study was designed to evaluate antimicrobial activity and chemical composition of four different
plant essential oils i.e. Ginger oil (GiO), Black seed oil
(BSO), Oregano oil (OO) and Rose oil (RO) against different bacterial and fungal strains. Anti-microbial activities
of selected essential oils were determined by the microbiological technique using Agar well diffusion assay. After
in vitro study, most of the essential oils showed antimicrobial activity against all the selected pathogens. Among
all the tested oils, GiO showed strong antimicrobial
activity. GiO showed highest antimicrobial activity against
Shigella (119.79%), Enteococcus hirae (110.61%) and
Escherichia coli (106.02%), when compared with the
tetracycline (50 lg/mL) activity. However, Antifungal
activity of GiO was found to be present against Candida
albicans and Aspergilluas flavus, when compared with
clotrimazole (50 lg/mL) activity. Among all the selected
bacteria, BSO showed maximum antimicrobial activity
against the E. coli followed by Citrobacter freundii.
Moreover, BSO had highest zone of inhibition against the
C. ablicans (33.58%). OO indicated that, Shigella had the
highest sensitivity (12.6 ± 0.58, 131.25%), followed by E.
hirae (19.1 ± 0.61, 96.46%) and Salmonella typhi
(15.2 ± 0.27, 83.06%) when compared with tetracycline
& Syed Amir Ashraf
amirashrafy2007@gmail.com
1
Department of Clinical Nutrition, College of Applied
Medical Sciences, University of Hail, Hail 2440, Saudi
Arabia
2
Department of Pharmacology and Toxicology, College of
Pharmacy, University of Hail, Hail 2440, Saudi Arabia
3
Department of Food Technology, FEIS, Hamdard University,
Delhi 110062, India
123
activity. OO showed poor sensitivity against all the selected fungal strains. Furthermore, Gas Chromatography
analysis revealed that, Gingerol (10.86%) was the chief
chemical constituents found in GiO followed by aSesquiphellandrene (6.29%), Zingiberene (5.88%). While,
BSO, OO and RO had higher percentage of p-Cymene
(6.90%), Carvacrol (15.87%) and Citronellol (8.07%)
respectively. The results exhibited that the essential oils
used for this study was the richest source for antimicrobial
activity which indicates the presence of broad spectrum
antimicrobial compounds in these essential oils. Hence,
essential oils and their components can be recommended
for therapeutic purposes as source of an alternative
medicine.
Keywords Antimicrobial activity Gas chromatography
Essential oils Agar well assay Bioactive compounds
Introduction
Despite a long periods mankind has searched for cure and
treatment of different diseases and has been used several
medicinal plant and their derived products. In recent years,
considerable efforts have been made to control the spread
of pathogens with various strategies, including the use of
alternative antimicrobial compounds (Raquel et al. 2012).
As the pipeline of development for newer antibiotics look
bleak, therefore the focus has been shifted towards the
development of non-antibiotic substances such as plant or
plant-derived products like essential oils (Sonboli et al.
2004). The essential oils and their principle constituents
have shown good fighting potential against drug resistant
pathogens (Ahmad and Beg 2001; Chavan et al. 2006).
Scientifically these essential oils have been proven
J Food Sci Technol (November 2017) 54(12):3948–3958
extremely potent antimicrobial agents in comparison to
antibiotics (Ravi et al. 2010). Due to their antimicrobial
activity, these natural ingredients appear as a viable and
healthy alternative to synthetic antibiotics for the treatment
of different diseases. Essential oils are aromatic oily liquids, which was obtained from various parts of plant by
different techniques. Steam distillation method is most
commonly used for commercial production of essential
oils. Around 3000 essential oils are known, from which 300
are commercially available (Seenivasan et al. 2006; Ravi
et al. 2010). A large number of essential oils have been
investigated for their antimicrobial properties and these
essential oils have showed good capability of controlling
the growth of microorganisms related to skin, dental caries
and food spoilage against the gram-negative and grampositive bacteria, fungi and yeasts (Johnson et al. 2013).
Active compounds produced by essential oils during secondary vegetal metabolism are usually responsible for such
biological activity and due to these bioactive components;
these essential oils are effective as antimicrobial agent
(Silva et al. 2010; Biljana et al. 2011). The growing interest
in the use of essential oils in food and pharmaceutical
industries, Ginger oil (GiO), Black seed oil (BSO), Oregano oil (OO) and Rose oil (RO) has become important
source of investigation against pathogen causing food
borne illnesses (Baratta et al. 1998).
Ginger (Zingiber officinale) oil has long been used as
naturopathy due to their potential antimicrobial activity as
well as different biological activities (Yuva 2014). The
medicinal properties have been mainly used for treating the
symptoms of vomiting, diarrhea, light-headedness, blurred
vision, dyspepsia, tremors, decrease in body temperature
and high blood pressure (Ishiguro et al. 2007). The
chemical composition of essential oils of ginger has been
identified and quantified by means of GC–MS (Gas Chromatogrpahy–mass spectrometry) or GC (Gas Chromatogrpahy) with flame ionization detector applications and
carried out works concerning the composition of essential
oils. The essential oil of ginger has been used as a medicine
against several problems, such as a cure for swelling, sores
and loss of appetite, stomach ache, diarrhea, tooth ache,
gingivitis arthritis, asthmatic respiratory disorders and
motor diseases, also possessing anti-inflammatory activity.
Some of these functional properties are generally attributed
to the gingerol (Sultan et al. 2005; Kamaliroosta et al.
2013). Black seed (Nigella sativa L.) oil has been known
for centuries in the Middle East, Eastern Europe, Asia and
Africa as a natural remedy for many ailments (Mohamed
and Eman 2012). In vivo and in vitro studies revealed
many pharmacological actions for BSO. These include
immune system stimulation, anti-inflammatory properties,
anti-cancer activity, anti-microbial activity, anti-parasitic
activity, anti-oxidant effect, hypoglycemic effect,
3949
galactagogue, carminative and laxative effects (Randhawa
and Al-Ghamdi 2002). The oil and its constituents are well
documented as antimicrobial agents. The essential oils are
complex mixtures of the compounds which mainly contain
monoterpenes, sesquiterpene hydrocarbons (Gerige et al.
2009). Oregano (Origanum vulgare) is one of the most
commonly known culinary herbs worldwide used for
cooking purposes. The dried herbs are used in many processed foods such as alcohol beverages, meat products,
snack foods, and milk products. Some of the Origanum
spp. is also used as a fragrance component in soaps,
detergents, perfumes, cosmetics, flavorings, and pharmaceuticals. Oregano oil has anti-bacterial, anti-fungal, antiparasitic, anti-microbial and antioxidant properties (Afef
et al. 2013). Chemical analysis of the OO revealed the
presence of several ingredients, most of which possess
important antioxidant and anti-microbial properties. Carvacrol and thymol are the two main phenols, which was
principally responsible for the antimicrobial activity (Maria
et al. 2015). Traditionally, rose oil has been demonstrated
to possess anti-inflammatory, skin protective and anti-aging effects as well as anti-bacterial activities (Milka et al.
2014). Rose oil is mainly used in the perfumery and cosmetics industry as a base component of modern perfumes
but it also finds application in the food industry as a flavor
additive (Kamran et al. 2014).
Therefore, this study was carried out to find the
antimicrobial potential of four important essential oils
against 23 Gram negative bacteria, Gram positive bacterial
and fungal strains. This study was undertaken to see the
potential effectiveness of selected essential oils as an
antimicrobial agents for a specific bacterial and fungal
strains. In addition to that, Identification of chemical constituents present in essential oils was also studied using gas
chromatography-mass spectrophotometry (GC–MS).
Material and methods
Bacterial strain
All the bacterial and fungal strains such as Rhodococus
equi (ATCC 6939), Bacillus cereus (MTCC 430), Enteococcus faecalis (MTCC 439), Staphylococcus aureus
(MTCC 96), Listeria monocytogenes (ATCC 19111),
Escherichia coli (ATCC 15597), Enterobacter aerogenes
(MTCC 111), Cronobacter sakazakii (ATCC 29544),
Klebsiella pneumonia (MTCC 109), Pseudomonas aeruginosa (MTCC 741), Citrobacter freundii (MTCC 1658),
Clostridium perfringens (MTCC 450), Micrococcus luteus
(MTCC 2470), Salmonella typhi (MTCC 733), Vibrio
parahaemolyticus (ATCC 17802),Vibrio cholera MTCC
(3906), Salmonella enterica (MTCC 733), Shigella (MTCC
123
3950
1457), Enteococcus hirae (ATCC10541), Listeria ivanovii
(ATCC 19119), Listeria innocua (ATCC 33090), Aspergillus niger (MTCC 2196), Aspergillus flavus (MTCC
2798), Candida albicans (ATCC 10231) Penicillium
pinophilium (MTCC 2192) and Saccharomyces cerevisiae
(MTCC 786) were procured. ATCC (American Type
Culture Collection) strains were obtained from LGC Promochem, Banglore, India. While MTCC strains were
obtained from Institute of Microbial Technology
(IMTECH), Chandigarh, INDIA.
Procurement of essential oils
Selected essential oils (GiO, BSO, OO and RO) were
purchased during November 2015 from the local market of
Hail, Kingdom of Saudi Arabia. These oils were selected
based on literature survey and their use in traditional
medicine. Quality of the oils was ascertained to be more
than 98% pure.
J Food Sci Technol (November 2017) 54(12):3948–3958
Gas chromatography mass spectrometry (GC–MS/
MS)
The essential oils were analyzed using GC–MS/MS
(Thermo Scientific, Triple quadropole MS, TSQ 8000) with
two
fused
silica
capillary
column
TG-5MS
(30 m 9 0.25 mm 9 0.25 lm). Injector and detector
temperatures were set at 220 and 250 °C, respectively. One
micro-liter oil samples diluted with methanol were injected
and analyzed with the column held initially at 50 °C for
1 min and then increased by 5 °C/min up to 280 °C.
Helium was employed as carrier gas (1 mL/min). The
identification of the different compounds was performed by
comparison of their relative retention times and mass
spectra with those of authentic reference compounds using
NIST (National Institute of Standards and Technology)
library database. Identification of chemical constituents
present in essential oils was investigated using gas chromatography-mass spectrophotometry (GC–MS).
Culture medium and inoculum preparation
Results and discussion
The test organisms were sub-cultured onto fresh plates of
Mueller–Hinton agar (Hi Media laboratories) for 24 h and
Sabouraud dextrose agar (Hi Media laboratories) for
5–7 days at 37 °C for bacteria and fungi, respectively.
Colonies from these plates were suspended in Mueller–
Hinton broth and Sabouraud broth to a turbidity matching
0.5 McFarland standard (108 cfu/mL). The media used for
antimicrobial assays were Mueller–Hinton agar for bacteria
and Sabouraud dextrose agar for fungi. All were incubated
appropriately as specified for each organism for a period of
18–24 h (Burt 2004).
Agar well diffusion assay
The antibacterial activities of the selected essential oils
were determined by Agar well diffusion assay techniques
(Reeves 1989). In this method, 100 lL of standardized
inoculum of each test bacterium were spread onto sterile
Muller–Hinton Agar and Sabouraud Dextrose Agar for
bacteria and fungus respectively. 8 mm diameter well was
cut from the agar using a sterile cork-borer; subsequently
each well was filled with 100 lL of the essential oils. The
plates were kept at room temperature for 1 h to allow
proper diffusion of the oil into agar and then incubated at
37 °C for 24 h and 30 °C for 3–5 days respectively.
Triplicates were prepared for each sample. The essential
oils having antimicrobial activity inhibit the microbial
growth and the clear zones were formed. The zone of
inhibition was measured in millimeters (Raid et al. 2014).
The percentage activities of essential oils were calculated
against standard drugs which was considered as 100%.
123
In the present study, evaluation of selected essential oils
(GiO, BSO, OO and RO) for their antimicrobial activities
and identification of chemical composition were carried out
using agar well diffusion technique and Gas chromatography, respectively. The antimicrobial activity was assessed by measuring the zone of inhibition as shown in Fig. 1
and results of antimicrobial activity were presented in
Fig. 2 and Table 1, while the identification of chemical
constituents were analyzed by relative percentage of the
total chromatogram area of oils as presented in (Table 2).
To avoid the possible effects of the solvent on the
antimicrobial property, commercially available essential
oils were not diluted and chemically not altered by any
solvent.
Antimicrobial activity of essential oils
Essentials oils have been tested for in vitro antimicrobial
activity and demonstrated to have potential antimicrobial
effect (Fig. 2; Table 1). The results obtained during this
study showed that, the zone of inhibition (mm) for the GiO
varied from (5.9 ± 0.19 mm) to (24.2 ± 0.24 mm) as
compared to standard tetracycline and clotrimazole
(18.2 ± 0.31 mm) to (37.5 ± 0.19 mm) respectively. The
antimicrobial activity of the GiO was found to be highest
against Shigella (119.79%), E. hirae (110.61%) and E. coli
(106.02%), when compared with the tetracycline activity.
Among all the fungal strains tested, Aspergillus flavus was
found to be most sensitive followed by C. albicans and A.
niger towards GiO. While, the lowest activity was recorded
J Food Sci Technol (November 2017) 54(12):3948–3958
3951
Fig. 1 Antimicrobial activity of Ginger oil (GiO), Black seed oil (BSO), Oregano oil (OO) and Rose oil (RO) against different bacterial strains
by using Agar diffusion method
120
GiO
BSO
OO
RO
Clotrimazole (50 µg/ml)
100
% Inhibition
Fig. 2 Antifungal activity of
essential oils using Agar
diffusion method
80
60
40
20
0
A niger
A. flavus
C. albicans
P. pinophilium
S. cerevisiae
Microorganism
against L. monocytogenes. Klebsiella pneumoniae showed
poor sensitivity to GiO as compare to the other Gramnegative bacteria. Our result showed that GiO stood more
effective as an antibacterial agent compared to antifungal
activity. Bellik (2014) reported that, GiO were more
effective against E. coli, Bacillus subtilis and S. aureus,
and least effective against A. niger. This result was in
conformity with the previous studies, which reported that
GiO exhibited an inhibitory effect against a wide range of
pathogenic bacteria and fungi. Their effect was probably
due to their active constituents such as Zingeberene, endoBorneol and Gingerol present in GiO (Amel et al. 2015).
123
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J Food Sci Technol (November 2017) 54(12):3948–3958
Table 1 Antibacterial activity of essential oils using Agar diffusion method
Micro-organism
Zone of inhibition in diameter (mm) and percentage
GiO
BSO
OO
RO
Tetracycline (50 lg/mL)
Rhodococus equi
17.2 ± 0.31 (77.13%)
5.1 ± 0.29 (22.87%)
15.1 ± 0.52 (67.71%)
NZ
22.3 ± 0.31
Bacillus cereus
19.4 ± 0.22 (62.38%)
7.5 ± 0.16 (24.12%)
18.4 ± 0.28 (59.16%)
NZ
31.1 ± 0.36
Enteococcus faecalis
15.3 ± 0.25 (61.94%)
4.5 ± 0.29 (18.22%)
10.7 ± 0.32 (43.32%)
NZ
24.7 ± 0.27
Bacillus cereus
19.4 ± 0.22 (62.38%)
7.5 ± 0.16 (24.12%)
18.4 ± 0.28 (59.16%)
NZ
31.1 ± 0.38
Staphylococcus aureus
17.9 ± 0.31 (66.05%)
4.6 ± 0.16 (16.94%)
16.1 ± 0.25 (59.41%)
NZ
27.1 ± 0.32
Listeria monocytogenes
5.9 ± 0.19 (29.79%)
2.0 ± 0.00 (10.10%)
5.0 ± 0.00 (25.25%)
NZ
19.8 ± 0.22
Escherichia coli
Enterobacter aerogenes
22.9 ± 0.16 (106.02%)
19.4 ± 0.33 (76.98%)
6.8 ± 0.39 (31.48%)
4.0 ± 0.32 (15.87%)
10.5 ± 0.31 (48.61%)
8.9 ± 0.24 (35.32%)
NZ
NZ
21.6 ± 0.39
25.2 ± 0.41
22.6 ± 0.37
Cronobacter sakazakii
12.7 ± 0.72 (56.19%)
4.1 ± 0.19 (18.14%)
12.0 ± 0.64 (53.09%)
NZ
Klebsiella pneumonia
12.5 ± 0.61 (66.49%)
3.5 ± 0.38 (18.62%)
9.2 ± 0.15 (48.93%)
NZ
18.8 ± 0.26
Pseudomonas aeruginosa
16.2 ± 0.47 (83.51%)
4.2 ± 0.56 (21.65%)
14.1 ± 0.18 (72.68%)
NZ
19.4 ± 0.32
Citrobacter freundii
15.8 ± 0.61 (67.52%)
7.2 ± 0.27 (30.77%)
12.5 ± 0.23 (53.42%)
NZ
23.4 ± 0.41
Clostridium perfringens
7.1 ± 0.62 (34.30%)
2.0 ± 0.00 (9.66%)
5.1 ± 0.25 (24.64%)
NZ
20.7 ± 0.26
Micrococcus luteus
24.2 ± 0.24 (82.03%)
8.1 ± 0.21 (27.46%)
18.6 ± 0.29 (63.05%)
NZ
29.5 ± 0.53
Salmonella typhi
18.1 ± 0.36 (98.91%)
3.0 ± 0.00 (16.39%)
15.2 ± 0.27 (83.06%)
NZ
18.3 ± 0.28
Vibrio parahaemolyticus
7.0 ± 0.22
2.0 ± 0.06
5.7 ± 0.19
NZ
NT
Vibrio cholerae
7.9 ± 0.42
2.5 ± 0.07
6.2 ± 0.28
NZ
NT
Salmonella enterica
16.9 ± 0.34 (92.86%)
2.8 ± 0.15 (15.38%)
14.5 ± 0.25 (79.67%)
NZ
18.2 ± 0.31
Shigella
11.5 ± 0.38 (119.79%)
2.0 ± 0.17 (20.83%)
12.6 ± 0.58 (131.25%)
NZ
9.6 ± 0.48
Enterococcus hirae
21.9 ± 0.37 (110.61%)
5.0 ± 0.08 (25.25%)
19.1 ± 0.61 (96.46%)
NZ
19.8 ± 0.36
Listeria ivanovii
7.4 ± 0.66
2.5 ± 0.006
5.9 ± 0.45
NZ
NT
Listeria innocua
8.4 ± 0.62
2.9 ± 0.24
6.55 ± 0.22
NZ
NT
Values are expressed as Mean value ± SEM (standard error of means) and Percentage inhibition
* NZ no zone of inhibition
** NT not tested
The antimicrobial activity of BSO against different
microorganisms has been studied by several research
groups. Morsi (2000) reported the antibacterial activity of
BSO crude extracts against multi-drug-resistant organisms,
including Gram-positive bacteria like S. aureus and Gramnegative bacteria like P. aeruginosa and E. coli. Our results
showed that, BSO had more antifungal activity in C.
albicans (9.1 ± 0.28 mm) than other fungus like Aspergilluas flavus and A. niger (7.5 ± 0.43 mm and
7.2 ± 0.57 mm) correspondingly. However, in comparison
to fungal strains, tested gram positive and gram negative
strains showed lesser sensitivity towards BSO. Among all
the selected bacteria, BSO had highest antimicrobial
activity against the E. coli followed by C. freundii. Listeria
monocytogenes had lesser sensitivity (10.10%) compared
to tetracycline standard. The presence of biological active
compounds in BSO such as a-thujene, a- pinene, limonene,
thymoquinone, myristicin etc. contributed the antimicrobial activity (Gerige et al. 2009). Salman et al. (2008)
reported that the antimicrobial activity of this oil may be
attributed due to the presence of thymoquinone,
123
thymohydroquinone and thymole which possessed antimicrobial activity. Results of Oregano oil showed that, Shigella had the highest sensitivity (12.6 ± 0.58 mm),
followed by E. hirae (19.1 ± 0.61 mm) and S. typhi
(15.2 ± 0.27 mm) when compared with standard tetracycline zone of inhibition 9.6 ± 0.48 mm, 19.8 ± 0.36 mm
and 18.3 ± 0.28 mm respectively. While, among Grampositive bacteria, L. monocytogenes showed least zone of
inhibition (5.0 ± 0.00 mm). OO showed good response
against Candida albicans with the zone of inhibition
10.4 ± 0.47 mm. Moreover, A. niger showed slight resistance towards OO when compared with other fungus
strains.
Our results showed that the OO had potential antibacterial activity against all the tested micro-organism
(Table 1). The highest activity was observed against Shigella with the strongest inhibition zones, followed by S.
typhi, when compared with standard tetracycline. Several
reports have been attributed the antimicrobial effectiveness
of OO was due to thymol, eugenol and carvacrol (Magdalena et al. 2011). Our chemical analysis found that the
J Food Sci Technol (November 2017) 54(12):3948–3958
3953
Table 2 Compounds identified in the essential oil using Gas chromatography mass spectrophotometry (GC–MS)
RT
Compound name
Molecular formula
SI
RSI
Area (%)
Identification
7.25
Eucalyptol
C10H18O
855
864
1.37
MS, RI
9.41
endo-Borneol
C10H18O
949
949
1.19
MS, RI
9.68
a-Terpineol
C10H18O
903
915
0.79
MS, RI
9.81
Decanal
C10H20O
889
889
2.22
MS, RI
11.46
1-Triethylsilyloxyheptadecane
C23H50OSi
661
775
1.11
MS, RI
13.06
ç-Elemene
C15H24
897
906
0.63
MS, RI
13.73
a-Copaene
C15H24
877
887
1.79
MS, RI
13.81
n-Hexadecanoic acid
C16H32O2
836
856
2.38
MS, RI
13.97
Alloaromadendrene
C15H24
892
897
4.20
MS, RI
14.17
14.52
a-Sesquiphellandrene
Cubenol
C15H24
C15H26O
891
868
893
903
6.29
1.44
MS, RI
MS, RI
14.59
(n)-trans-Nerolidol
C15H26O
907
938
0.93
MS, RI
14.97
7-epi-cis-sesquisabinene hydrate
C15H26O
891
905
2.87
MS, RI
15.24
cis-sesquisabinene hydrate
C15H26O
848
860
2.21
MS, RI
15.64
4-(3-Hydroxy-2-methoxyphenyl)-2-butanone
C11H14O3
937
940
3.71
MS, RI
15.80
Eudesm-4(14)-en-11-ol
C15H26O
861
874
1.40
MS, RI
18.83
(-)-Zingiberene
C15H24
895
930
10.86
MS, RI
20.59
Linoleic acid, methyl ester
C19H34O2
880
889
14.38
MS, RI
24.02
a-Curcumene
C15H22
891
896
4.27
MS, RI
25.11
a-Farnesene
C15H24
874
895
4.04
MS, RI
27.66
Gingerol
C17H26O4
677
704
7.88
MS, RI
5.58
2-Thujene
C10H16
927
947
2.78
MS, RI
6.32
a-Pinene
C10H16
649
680
1.08
MS, RI
7.11
p-Cymene
C10H14
918
931
6.90
MS, RI
7.64
8.60
ç –Terpinene
cis-4-methoxy thujane
C10H16
C11H20O
916
915
927
941
1.14
1.81
MS, RI
MS, RI
GiO
BSO
10.52
Thymoquinone
C10H12O2
913
913
2.07
MS, RI
11.03
Anethole
C10H12O
924
929
0.96
MS, RI
11.20
Carvacrol
C10H14O
922
924
0.76
MS, RI
12.82
Longifolene
C15H24
905
918
0.50
MS, RI
14.45
Apiol
C12H14O4
785
815
0.39
MS, RI
18.83
l-(?)-Ascorbic acid 2,6-dihexadecanoate
C38H68O8
846
847
14.51
MS, RI
20.56
Linoleic acid, methyl ester
C19H34O2
880
889
13.95
MS, RI
25.18
Myristicine
C17H34O2
884
898
1.05
MS, RI
27.65
Limonene
C14H28O2
867
880
0.71
MS, RI
5.63
2-Thujene
C10H16
923
943
1.22
MS, RI
5.71
a-Pinene
C10H16
919
927
1.88
MS, RI
6.54
Thymol
C10H16
823
833
2.52
MS, RI
7.12
7.65
ç-Terpinene
p-Cymene
C10H16
C10H14
917
903
919
919
7.98
5.46
MS, RI
MS, RI
8.12
p-Cymenene
C10H12
728
870
0.84
MS, RI
8.25
a-Linalool
C10H18O
920
921
4.02
MS, RI
9.06
4-Ethyloctane
C10H22
760
904
1.29
MS, RI
9.50
Terpinen-4-ol
C10H18O
884
885
2.01
MS, RI
9.71
Dodecane
C12H26
791
876
1.84
MS, RI
OO
123
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J Food Sci Technol (November 2017) 54(12):3948–3958
Table 2 continued
RT
Compound name
Molecular formula
11.27
Carvacrol
C10H14O
12.97
Caryophyllene
C15H24
15.03
Caryophyllene oxide
C15H24O
16.09
1-Chloroeicosane
16.58
Eutanol G
25.80
Campesterol
27.65
Eugenol
RO
8.50
9.65
SI
RSI
Area (%)
Identification
874
874
15.87
MS, RI
908
915
2.08
MS, RI
800
835
2.02
MS, RI
C20H41Cl
682
688
0.91
MS, RI
C20H42O
798
826
3.64
MS, RI
C28H48O
757
778
0.92
MS, RI
C29H50O
806
815
2.55
MS, RI
a-Linalool
C10H18O
933
934
1.51
MS, RI
1-Octanol, 3,7-dimethyl
C10H22O
905
939
0.39
MS, RI
9.97
a-Citronellol
C10H20O
893
912
0.45
MS, RI
10.15
Citronellol
C10H20O
923
923
8.07
MS, RI
10.53
Geraniol
C10H18O
937
937
6.63
MS, RI
11.17
Linalool, formate
C11H18O2
775
778
0.47
MS, RI
12.00
3-Allyl-2-methoxyphenol
C10H12O2
931
931
0.88
MS, RI
13.21
Aristolene
C15H24
894
898
0.55
MS, RI
20.54
trans-Geranyl geraniol
C20H34O
741
789
3.70
MS, RI
23.09
Citronellyl formate
C11H20O2
844
920
1.42
MS, RI
27.29
l-Menthone
C10H18O
867
957
0.67
MS, RI
OO had highest percentage of Carvacrol, thymol and
eugenol, which could have played an important role for OO
antibacterial activity. RO were ineffective against all the
selected strains. Few researchers have been reported that
rose oil has very minimal antimicrobial activity. Balkan
et al. (2016) and (Mahboubi et al. 2016) had similar reports
corresponding to our results. No zone of inhibition recorded from RO, this could be due to source of oil origin,
production and probably due to differences in number of
active compounds and in their concentrations. Our result
showed that GiO stood more potent antimicrobial agents
among the selected oils.
Several mechanisms have been proposed to explain the
antimicrobial activity of essential oils. Various compounds
with antibacterial activity inhibit growth or cause bacterial
deaths or directly affect DNA synthesis. The bacterial cell
wall can be affected in various ways, which can be at
different stages of synthesis or transport of its metabolic
precursors, or by a direct action on its structural organization (Martinez-Martinez 2009). The mechanism of action
appears to be predominently on the cell membranes by
disrupting its structure thereby causing cell leakage and
cell death, secondary actions may be by blocking the
membrane synthesis and inhibition of cell respiration. They
readily penetrate into the cell membrane and exert their
biological effects because of high volatility and
liphophilicity of the essential oils (Aligiannis et al. 2001;
Oyedemi et al. 2009; lalit et al. 2012). Antimicrobial
123
testing will give us only an idea for presence of antimicrobial compound in essential oils by measuring zone of
inhibition. However, GC–MS analysis will be needed for
the identification of bioactive compound responsible for
the antimicrobial activity.
Analysis of chemical constituents by gas
chromatography
The results of the GC–MS/MS analysis identified various
compound present in essential oils (GiO, BSO, OO and
RO). The major compound in the methanolic extract were
identified and listed in Table 2. Identification was done by
direct comparison of the retention times (RT) and mass
spectral data of compounds with their respective reference
compounds matched with the NIST (National Institute of
Standards and Technology) Library. Percentage areas of
the each component were measured.
Gas chromatography analysis of GiO identifies 36 peaks
(Fig. 4) out of which, major components were found to be
Zingiberene (10.86%), Gingerol (7.88%), a-Sesquiphellandrene (6.29%), a-Curcumene (4.27%), Alloaromadendrene (4.20%), a-Farnesene (4.04%), Eucalyptol (1.37%),
endo-Borneol (1.19%), Cubenol (1.44%). Zingiberene was
the most predominant compounds belonging to the
sesquiterpene hydrocarbon of the total extracted essential
oil. The specific aroma of ginger was predominantly
because of Zingiberene. Our findings were in agreement
J Food Sci Technol (November 2017) 54(12):3948–3958
3955
Fig. 3 Structure of major
compounds of the essential oils
of GiO, BSO, OO and RO
with previous work carried out by Sultan et al. (2005). GC–
MS analysis of BSO identified 29 constituents, out of
which l-(?)-Ascorbic acid 2,6-dihexadecanoate (14.51%),
p-Cymene (6.90%), 2-Thujene (2.78%), cis-4 methoxy
thujane (1.81), a-Pinene (1.08%), c-Terpinene (1.14%),
Thymoquinone (2.07%), Anethole (0.96%), Carvacrol
(0.76%), Longifolene (0.50%) and Apiol (0.39%) were the
major ones. These results were comparable to the qualitative test results obtained from previous studies (Mozaffari
et al. 2000; Gerige et al. 2009). Previous author reported,
thymoquinone 1.8% and p-cymene 9.0% which was in
accordance to our presented results (Dinagaran et al. 2016;
Gerige et al. 2009). Other studies also reported, p-cymene
14.8% and thymoquinone 0.6% (Nickavar et al. 2003). OO
were analyzed for Gas chromatography determination, 21
major peaks were identified. Carvacrol (15.87%) was the
highest, followed by ç-Terpinene (7.98%), p-Cymene
(5.46%), a-Linalool (4.02%) and Thymol (2.52%). These
percentages were higher than reported from Magdalena
et al. (2011). Afef et al. (2013) showed that this species is a
rich source of phenolic monoterpenes and carvacrol.
Considering that carvacrol-rich essential oils are gaining
increasing importance for their considerable antimicrobial
activity. Previous studies also showed that carvacrol was
high in concentration than thymol (Babili et al. 2011;
Milovanovic et al. 2009). Lower concentration of thymol
could be due to different extraction techniques due to
geographical sources. Our findings also suggested that, in
Oregano Oil (OO), carvacrol is present in rich amount than
thymol. Volatile oil of RO was analyzed and characterized
by very less numbers of monoterpenes and large numbers
of sesquiterpenes and aliphatic components. Major component identifies in RO was Citronellol (8.07%), Geraniol
(6.63%), Phenylethyl Alcohol (3.18%), trans-Geranylgeraniol (3.70%), Citronellyl formate (1.42%).These
results were in comparable with the previous studies (Kiran
and Babu 2002; Kamran et al. 2014). Major components
with their chemical structure presented in Fig. 3. The GC–
MS analysis showed that all the selected essential oils had
abundant bioactive compounds which could be of potential
use for further studies against pathogenic bacteria.
Conclusion
The present investigation was aimed to study the antimicrobial activity of (BSO, GiO, OO and RO) against 23
Gram-positive bacteria, Gram-negative bacteria and Fungi.
123
3956
Fig. 4 GC–MS chromatogram of a GiO, b BSO, c OO and d RO
123
J Food Sci Technol (November 2017) 54(12):3948–3958
J Food Sci Technol (November 2017) 54(12):3948–3958
The antimicrobial activity of these tested essential oils,
against the micro-organisms may be indicative of the
presence of broad spectrum antimicrobial compounds
present in these oils. Although this study investigated the
in vitro antimicrobial activity, the results substantiate the
use of four studied essential oils as antimicrobial agents for
the treatment of various bacteria or fungal related diseases.
In conclusion, it is suggested that these plants may be
useful to discover natural bioactive compounds. More
importantly, these can be included in the list of herbal
medicines due to their high antimicrobial potential and
lesser side effects. Hence, essential oils and their components can be recommended for therapeutic purposes and
can be used as an alternative source of medicine.
Acknowledgements We are grateful to the Department of Food
technology, Hamdard University, New Delhi and Department of
Clinical Nutrition, College of Applied Medical Sciences, Hail
University for providing facilities to carrying out the present study.
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