African Journal of Biotechnology Vol. 11(95), pp. 16192-16195, 27 November, 2012
Available online at http://www.academicjournals.org/AJB
ISSN 1684–5315 ©2012 Academic Journals
Full Length Research Paper
Effect of temperature on antibiotic properties of
garlic (Allium sativum L.) and ginger
(Zingiber officinale Rosc.)
Pankaj Sah*, Balqees Al-Tamimi, Najat Al-Nassri and Rahma Al-Mamari
Department of Applied Sciences (Applied Biology Section), Higher College of Technology, Al-Khuwair,
P. O. Box 74, PC 133, Muscat, Sultanate of Oman.
Accepted 26 October, 2012
Garlic and ginger are the two most common herbs used in traditional medicine practice for their
antimicrobial activities. Moreover, in many countries, they are also used with boiled food preparations,
which can destroy their important medicinal properties. We conducted an agar well diffusion assay with
aqueous extracts of garlic and ginger to observe the effect of temperature on their antibiotic properties
against three human pathogenic bacteria namely Klebsiella pneumoniae, Escherichia coli and
Staphylococcus aureus. The results show that in general, garlic has significantly greater zone of
inhibition (mean = 23.3 mm) than ginger (mean = 19.0 mm) at both, room temperature (26°C) (t = 4.91; α
= 0.05; P < 0.01) and at higher temperature (100°C); garlic (mean = 15.6 mm); ginger (mean = 0 mm) (t =
17.76; df = 2; α = 0.05; P < 0.001). On observation, it was found that although higher temperature
significantly reduced the antibacterial properties of both plants, nevertheless it affected ginger more (t
= 32.9, df = 2; α = 0.05; P < 0.001) than garlic (t = 11.5, df = 2; α = 0.05; P < 0.01). From our study, we can
conclude that garlic has more prevailing and sustainable antibiotic properties than ginger under normal
and higher temperature regimes. We recommend that garlic not only has very promising potential for a
broad-spectrum antibiotic drug against many pathogenic bacteria, but also significantly sustains its
antibacterial property than ginger even with boiled food preparations. In addition, it can be used as an
effective source of natural herbal antibiotics with or without boiling.
Key words: Garlic, ginger, medicinal plants, antibiotic properties, naturopathy.
The augmented usage of antibiotic medicines has given a
chance to many bacteria to develop antibiotic resistance
in their populations. Besides,
development of resistance to chemotherapeutic agents is
increasingly becoming a burning predicament (Abimbola
et al., 1993). Consequently, there is an urgent need to
unearth the potential antimicrobial materials, especially
plants and their parts as they are natural, easily available
and do not have any side-effects too. Many plants and
their parts are used for various medicinal properties in
traditional system of medicine (Khulbe and Sati, 2009).
Various scientists have focus on determining the
*Corresponding author. Email:
antimicrobial activity of plant extracts found in folk
medicine, essential oils or isolated compounds such as
alkaloids, flavonoids, sesquiterpene lactones, diterpenes,
triterpenes or naphtoquinones, among others. Some of
these compounds have been isolated or obtained by bio-
guided isolation after previously detecting antimicrobial
activity on the part of the plant. A second block of studies
focuses on the natural flora of a specific region or
country; the third relevant group of school is made up of
specific studies of the activity of a plant or principle
against a concrete pathological microorganism (Rios and
Recio, 2005). In ethnobotanical literature, both the aerial
and root parts have been used as an antiseptic. It has
been observed that the leaf part of some plants is
effective on cuts and wounds, whereas root powder is
being used as antiseptic (Gaur, 1999). Even in traditional
medicinal practice, people use many herbs as an
Sah et al. 16193
Table 1. Effect of temperature on the antibacterial activity of Garlic and Ginger.
Inhibition zone (mm)a
Klebsiella pneumoniae (Gram negative)
Escherichia coli (Gram negative)
Staphylococcus aureus (Gram positive)
aData are the average of three experiments.
Garlic (Allium sativum) and ginger (Zingiber officinale)
are the two most common plants used in naturopathy.
However, in many countries people use these plants
along with boiled food preparations, which destroy the
plants’ important antibacterial agents. The objective of
this study was to understand how temperature affects the
strength and sustainability of antibiotic properties in garlic
MATERIALS AND METHODS
The study was carried out on common garlic, A. sativum (Alliaceae)
and common ginger, Z. officinale Rosc. (Zingiberaceae) plant parts
(bulb and rhizome, respectively). A. sativum, the common garlic,
has traditional dietary and medicinal applications as an anti-
infective agent (Lawson, 1998; Reuter et al., 1996). In vitro
evidence of the antimicrobial activity of fresh and freeze-dried garlic
extracts against many bacteria (Cavallito and Bailey, 1944; Rees et
al., 1993), fungi (Adetumbi et al., 1986), and viruses (Weber et al.,
1992) lends support to these applications. On the other hand, Z.
officinale Rosc. (Zingiberaceae), the common ginger, has a direct
inhibitory effect on microbial organisms and it has been used for
centuries to fight against bacterial infections (Tan and Vanitha,
2004). In the past few decades, the search for new anti-infection
agents has occupied many research groups in the field of
ethnopharmacology (Rios and Recio, 2005).
Agar well diffusion assay
The present agar well diffusion assay was carried out to investigate
the effect of temperature on the antibacterial properties of garlic
and ginger, since in many countries these herbs are used with
boiled food preparations. We assume that a comparison between
the antibacterial properties of these two widely used herbs along
with increasing temperature would help to use the herbs more
effectively. First of all, 215 g of garlic bulb and ginger rhizome were
weighed and the skin was removed with a sharp knife. They were
washed at room temperature with distilled and sterilized water. Both
herb species were cut into small pieces and ground in blender to
obtain juice separately. Afterward, the juice was passed through
sterilized filter paper and funnel, and then filtered by vacuum
suction pump using Millipore filter paper of 0.45 µM pore size. The
same process was repeated again and the cut pieces of both herbs
were immersed in boiling water (100°C) for 30 min to see the effect
of temperature. Then, the juice was extracted for the heat-treated
garlic and ginger.
The agar well assay method was used to explore the
antimicrobial activity of both plant parts. Nutrient agar medium was
prepared in Petri-plates to grow the test microorganisms. We
compared the difference in antibiotic activities of both plant extracts
at 100 µg/ml concentration under normal room temperature (26°C)
and at boiling water (100°C) conditions. The test microorganisms
Escherichia coli and Klebsiella pneumoniae (both Gram negative)
and Staphylococcus aureus (Gram positive) were obtained from the
Department of Applied Sciences (Applied Biology Laboratory),
Higher College of Technology (HCT), Al Khuwair, Muscat
(Sultanate of Oman). The test bacteria were streaked on the
nutrient agar plate in laminar flow under sterilized conditions. A hole
of 10-mm diameter was made at the centre of plate by sterilized
core borer (Srinivasan et al., 2001) and 100 µL of each extract was
dropped in the hole using micropipettes. Each plant extract was
tested in triplicate to take the average values. All inoculated agar
plates were incubated at 37°C for 24 h in the incubator (Khulbe and
Sati, 2009). The antibacterial activities of both garlic and ginger
were observed from the size of diameter of “zone of inhibition” (ZI),
measured in mm.
RESULTS AND DISCUSSION
A paired t-test analysis was performed for the
comparison of antibiotic strength and its sustainability
and results show that the antibiotic activities of garlic (A.
sativum) was significantly greater (mean = 23.3 mm)
under normal room temperature than in boiled conditions
(mean = 15.6 mm), with a mean difference of 7.6 mm
(Table 1) (t = 11.5, df = 2; α = 0.05; P < 0.01). The
decrease in antibacterial property can be clearly
elucidated, as it is a well established verity that the loss
of antibacterial activity of natural products by heating may
be due to volatilization and/or the physical and chemical
changes that occur during heating (Durairaj et al., 2009).
Apart from high temperature (heating), there can be
some other reasons for the reduction in antibacterial
activity. For example, researchers have given other
reasons for reduction in ginger’s antibacterial activity like
reduction of allicin to diallyl disulfide (Reuter et al., 1996).
Similar trends were also observed for the antibiotic
activities of ginger (Zingiber officinale) where it was
significantly greater under normal room temperature
(mean = 32.9 mm) than in boiled conditions (mean = 0
mm), with a mean difference of 19 mm (Table 1) (t =
32.90, df = 2; α = 0.05; P < 0.001). In the present study,
boiled ginger also lost its antibacterial activity immensely,
which can be due to volatilization of its active
compounds. When both plant species were treated with
boiled water (100°C) for 30 min, clear reductions in their
antibiotic properties were observed. It was observed that
16194 Afr. J. Biotechnol.
even in high temperature, garlic (A. sativum) was able to
sustain its antibiotic properties. On the other hand, ginger
(Z. officinale) totally lost its antibiotic properties against
the studied bacterial species.
Increasing temperature deteriorated the antibacterial
properties of ginger drastically, but did not affect garlic in
similar fashion. In higher temperature of 100°C, garlic (A.
sativum) proved to have significantly greater antibiotic
activities (t = 17.76; df = 2; α = 0.05; P <0.001) than
ginger (Z. officinale). Comparison between the antibiotic
activities of garlic (A. sativum) and ginger (Z. officinale),
at both temperatures [under normal room temperature
(26°C) and boiling water temperature (100°C)], the paired
sample t-test analysis proved that garlic (A. sativum) had
significantly greater (mean = 22 mm) antibacterial
properties at 26°C (t = 7; df = 1; α = 0.05; P < 0.05) than
ginger (Z. officinale) (mean = 18.5 mm). Even in the
increased temperature of 100°C, garlic (A. sativum) had
significantly greater (mean = 15 mm) antibacterial
properties (t = 15; df = 1; α = 0.05; P < 0.05) than ginger
(Z. officinale) (mean = 0 mm) (Table 1). So, it was found
that garlic had stronger and sustainable antibiotic
activities than ginger at 26 and 100°C temperature [t =
11.5, df = 2; α = 0.05; P < 0.01) and (t = 17.76; df = 2; α =
0.05; P <0.001)], respectively.
Our findings have shown that garlic retained its
antibacterial activity even with high temperature
treatments. In a recent research, while understanding the
effect of temperature on the antibacterial activities of
garlic and cinnamon, it was found that in most of the
studied bacteria (Bacillus cereus and E. coli) both garlic
(A. sativum) and cinnamon (Cinnamomum zeylanicum)
retained their antibacterial activity till 120°C (Ranjan et
al., 2012). Our results support that garlic retained its
antibacterial properties even in higher temperature, thus
establishing the superiority of garlic’s antibacterial activity
over ginger in terms of temperature treatment. This also
supports the earlier effective antibacterial findings of Indu
et al. (2006) that garlic has more potential as an antibiotic
herb than ginger. In their study, Indu et al. (2006) found
that garlic extract even presented higher diameter of
inhibition zones than many known antibiotic drugs like
ciprofloxacin, chloramphenicol, tetracycline, streptomycin
and nalidixic acid. The antibacterial activity of garlic is
reported to be due to the action of allicin or diallyl
thiosulphinic acid or diallyl disulphide (Avato et al., 2000).
It is postulated that the antibacterial and antifungal
properties of garlic juice are due to the inhibition of
succinic dehydrogenase via the inactivation of thiol group
(Indu et al., 2006).
The present study shows that garlic’s antibacterial
activity did not cease even up to 100°C temperature. In a
contemporary research, Ranjan et al. (2012) found that
garlic and cinnamon can also be used as natural food
preservatives for fishes at room temperature, fried fishes
and even deep-fried fishes, since both plants retained
their antibacterial activity at very high temperature and
the “antibacterial activity index” of garlic and cinnamon
was more than 0.5 till 120°C. The findings of our research
are important as they elaborate the effective antibiotic
properties of garlic and its importance as a highly potent
natural drug source against many bacterial diseases,
which can be used even with boiled food preparations
also and of course, with its significant antibiotic effect.
The authors are highly grateful to the Ministry of
Manpower, Sultanate of Oman, Dean, Heads of Science
Department and Biology Section, Higher College of
Technology, Muscat; for their support during the course
of the study. Thanks are also due to all laboratory
technicians for helping in the smooth running of the
Abimbola KA, Obi CL, Alabi SA, Olukoya DK, Ndip RN (1993). Current
Status on biotyping antibiogram and plasmid profiles of E. coli
isolates. East Afr. Med. J. 70:207-210
Adetumbi M, Javor GT, Lau BHS (1986). Allium sativum (Garlic) inhibits
lipid synthesis by Candida albicans. Antimicrob. Agents Chemother.
Avato P, Tursil E, Vitali C, Miccolis V, Candido V (2000). Allylsulfide
constituents of garlic volatile oil as antimicrobial agents.
Cavallito CJ, Bailey JH (1944). Allicin, the antibacterial principle of
Allium sativum. I. Isolation, physical properties, and antibacterial
action. J. Am. Chem. Soc. 66:1950.
Durairaj S, Srinivasan S, Lakshmanaperumalsamy P (2009). In vitro
Antibacterial Activity and Stability of Garlic Extract at different pH and
Temperature. Elect. J. Biol. 5(1):5-10.
Gaur RD (1999). Flora of the District Garhwal North west Himalaya, 1st
ed.; Trans Media Publication.
Indu MN, Hatha AAM, Abirosh C, Harsha U, Vivekanandan G (2006).
Antimicrobial activity of some of the south-Indian spices against
serotypes of Escherichia coli, Salmonella, Listeria monocytogenes
and Aeromonas hydrophila. Braz. J. Microbiol. 37(2):153-158.
Khulbe K, Sati SC (2009). Antibacterial Activity of Boenninghausenia
albiflora Reichb. (Rutaceae). Afr. J. Biotechnol. 8(22):6346-6348.
Lawson LD (1998). Garlic: a review of its medicinal effects and
indicated active compounds. in Phytomedicines of Europe: their
chemistry and biological activity. ACS Symposium Series, no. 691.
eds Lawson LD, Bauer R. (American Chemical Society, Washington,
D.C.). pp. 176-209.
Ranjan S, Dasgupta N, Saha P, Rakshit M, Ramalingam C (2012).
Comparative study of antibacterial activity of garlic and cinnamon at
different temperature and its application on preservation of fish. Adv.
Appl. Sci. Res. 3(1):495-501.
Rees LP, Minney SF, Plummer NT, Staler JH, Skyrme DA (1933). A
quantitative assessment of the antimicrobial activity of garlic (Allium
sativum). World J. Microb. Biotechnol. 9:303-307.
Reuter HD, Koch HP, Lawson LD (1996). Therapeutic effects and
applications of garlic and its preparations. in Garlic. The science and
therapeutic application of Allium sativum L. and related species–
1996. eds Koch HP, Lawson LD (Williams & Wilkins, Baltimore, Md),
Rios JL, Recio MC (2005). Medicinal Plants and Antimicrobial Activity.
J. Ethnopharmacol. 100(1-2):80-84.
Srinivasan D, Sangeetha N, Suresh T, Lakshmanaperumalsamy P
(2001). Antimicrobial activity of certain Indian medicinal plants used
in folkloric medicine. J. Ethnopharmacol. 74:217-220.
Tan BKH, Vanitha J (2004). Immunomodulatory and Antibacterial
Effects of Some Traditional Chinese Medicinal Herbs: A Review.
Curr. Med. Chem. 11(11):1423-1430.
Sah et al. 16195
Weber ND, Anderson DO, North JA, Murray BK, Lawson LD, Hughes
BG (1992). In vitro virucidal effects of Allium sativum (garlic) extract
and compounds. Planata Med. 58:417-423.