Antibacterial Effect of Onion

Abstract

Onion (Allium cepa) is among the oldest cultivated plants, and is used for multiple purposes. In addition to its nutritional effects, the antioxidant and antimicrobial activities of onion has also been postulated, and continue to be extensively investigated. Therefore, this study was designed to investigate the possible antibacterial effects of three types of onions; red, green and white onion. Different concentration of each onion was prepared in water extraction form. Six types of bacteria were tested, and their selection was based upon their common involvement in causing infectious bacterial diseases among people who live in Saudi Arabia. These tested bacteria included methicillin-resistant Staphylococcus aureus (MRSA), methicillin-sensitive Staphylococcus aureus (MSSA), Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), Klebsiella species (Klebsiella Spp.), and Salmonella species (Salmonella Spp.). The antibacterial effects of each onion water extraction against these 6 bacteria species were carried out in vitro by using filter paper method, different agar in media containing different concentration of onion extrat method, suspension method and pieces of onion method. The results showed that the three types of onions had inhibitory effects on the growth of all investigated bacteria; however, their antibacterial effects were varies according to onion type and its water extraction concentration as well as on the type of tested bacteria.

Full text

DOI: 10.21276/sjams.2016.4.11.53
Available online at http://saspublisher.com/sjams/ 4128
Scholars Journal of Applied Medical Sciences (SJAMS) ISSN 2320-6691 (Online)
Sch. J. App. Med. Sci., 2016; 4(11D):4128-4133 ISSN 2347-954X (Print)
©Scholars Academic and Scientific Publisher
(An International Publisher for Academic and Scientific Resources)
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Antibacterial Effect of Onion
Mr. Ahmed M. Kabrah1, Dr. Hani S. Faidah2, Dr. Ahmad M Ashshi1, Mrs. Safaa A. Turkistani3
1Department of Laboratory Medicine, Faculty of Applied Medical Sciences, Umm Al-Qura University Makkah, Saudi
Arabia
2Department of Medical Microbiology, Faculty of Medicine, Umm Al-Qura University, Makkah, Saudi Arabia.
3PhD. Student Howard University, Department of Microbiology, Washington DC, United States of America
*Corresponding author
Mr. Ahmed M. Kabrah
Email: amkabrah@uqu.edu.sa
Abstract: Onion (Allium cepa) is among the oldest cultivated plants, and is used for multiple purposes. In addition to its
nutritional effects, the antioxidant and antimicrobial activities of onion has also been postulated, and continue to be
extensively investigated. Therefore, this study was designed to investigate the possible antibacterial effects of three types
of onions; red, green and white onion. Different concentration of each onion was prepared in water extraction form. Six
types of bacteria were tested, and their selection was based upon their common involvement in causing infectious
bacterial diseases among people who live in Saudi Arabia. These tested bacteria included methicillin-resistant
Staphylococcus aureus (MRSA), methicillin-sensitive Staphylococcus aureus (MSSA), Escherichia coli (E. coli),
Pseudomonas aeruginosa (P. aeruginosa), Klebsiella species (Klebsiella Spp.), and Salmonella species (Salmonella
Spp.). The antibacterial effects of each onion water extraction against these 6 bacteria species were carried out in vitro by
using filter paper method, different agar in media containing different concentration of onion extrat method, suspension
method and pieces of onion method. The results showed that the three types of onions had inhibitory effects on the
growth of all investigated bacteria; however, their antibacterial effects were varies according to onion type and its water
extraction concentration as well as on the type of tested bacteria.
Keywords: onion, antibacterial, MRSA, MSSA, E. coli Klebsiella Spp., P. aeruginosa
INTRODUCTION
The first cultivated vegetable all over the
centuries is the Allium family that is an amazing group
that has over 500 species different in the shape, color
and taste but they are close in their biochemical
components [1]. The most common Allium family
members are: Allium cepa (i.e., Onion), Allium stivum
(i.e., Garlic), Allium Fistulosum, Allium Ampeloprasum,
and Allium schoenoprasm [2].
Onion is the generic name of the Allium cepa
family. It was cultivated 6000 years BC in the nail
valley. It contains a lot of minerals and small number of
vitamins. It is used as food as well as for medicinal
purposes. As a medicine, it is better to use raw onions
because by boiling it loses its efficacy [3].
The onions have different uses as culinary and
therapeutic purposes. During World War II, Russian
soldiers used the onions as antiseptic in the battle
wounds. Recently, the onion still playing an important
role in our diet and medicinal use [4].
Onions have 25 active components, like the
sulphur which is the worthiest substance found in onion,
it acts as an anti-inflammatory, thiosulfinates also can
act as anti-thrombotic and superoxide-dismutase (SOD)
which act as an anti-oxidants [5, 6]. The cell wall of the
onion is rich with Uronic acid, glucose and smaller
amount of arabinose, xylose, fructose and galactose
which are found in the lower epidermis of the onion
scale [2]. On the other hand, the chemical components
can be classified into two groups: Alk(en)yl Cysteine
Sulphoxides(ACSOs) that gives the odour and
taste of the onion when it’s cleaved by allinase and two
Flavonoid subgroups, anthocyanins that gives the red or
the purple colour to the onion or the yellow colour
which is obtained by the querctin that is mainly present
as glycosides [6]. The querctin is a useful substance for
people suffering from arthrosclerosis, it inhibits the
Original Research Article

Ahmed M. Kabrah et al., Sch. J. App. Med. Sci., Nov 2016; 4(11D):4128-4133
Available online at http://saspublisher.com/sjams/ 4129
vascular smooth muscle cell Ca++ influx isorham [7],
netin-4-glucoside, xylose, mannose, organosulfur
compounds, allylsulfides, flavenols, cycloalliin and
selenium can be present also in the Onion [8, 9].
The glutathione is also found in the onion to promote
the metabolism ability of liver fat and improve the
complexion and texture of the skin by inhibiting the
formation of melanin. The mineral composition of
onion includes as calcium, magnesium, sodium,
potassium, selenium and phosphorus [6].
Onion represented a rich source of antimicrobial agents,
the French researcher and physician (Louis Pasteur)
first described the antibacterial effect of onion and
garlic juices [10]. Flavonoids founded in vitro had been
an effective antimicrobial substance against wide array
of microorganisms, such viruses and bacteria [11]. The
antiviral Function of flavonoids has been demonstrated
with the HIV virus, and also with a herpes simplex virus
(HSV-1), The phenolic acid compounds which is a
flavonoid derivatives prevented the development of
bacteria such as Bacillus cereus, Staphylococcus
aureus, Micrococcus luteus, Listeria monocytogenes
and all microorganisms typically associated with the
deterioration of foods by inhibiting of DNA gyrase [12].
Querectin derived products such 2-(3,4-
dihydroxyphenyl)-4,6-dihydroxy-2-
methoxybenzofuran-3-one presented had an activity
against Helicobacter pylori strains and 3-(quercetin-8-
yl)-2,3-epoxyflavanone showed antibacterial activity
against MRSA and H. pylori strains at the same time
which increased susceptibility of MRSA to beta-lactams
[13].
There were also observed that raw onion had
activity only on Pseudomonas aeruginosa and
salmonella but no effect on Staphylococcus aureus,
Escherichia coli and Bacillus subtilis. In contrast the
hot water extracts of onion did not inhibit the growth
Pseudomonas aeruginosa neither Salmonella this might
be due to the destruction of phinolic compounds by heat
from the hot water [14]. Onion extract had different
inhibition levels against S. aureus and S.enteritidis. In
the dose response study, the inhibition zone increased
with increasing concentration of extracts. Low
concentrations inhibited weakly the development of
bacteria; however S.enteritidis was more sensitive than
S. aureus at high concentrations Otherwise S.aureus is
less sensitive than S.enteritidis which was more
inhibited at the same concentration [5]. On the other
hand, the onion extract had also an antifungal effect on
Aspergillus niger, Penicillium cyclopium and less
inhibition of Fusarium oxysporum due to
thiosulfunides. Researchers reported that allicin found
in the Allium was effective against Candida,
Cryptococcus, Trichophyton, Epidermophyton and
Microsporum [14]. The minimum inhibitory
concentration is affected by the incubation time,
inoculum size, pH and type of medium. There is an
inverse increase relationship between the inoculum size
and susceptibility; they also observed that the allicin
had an antifungal activity which was strong in
Sabouraud glucose agar medium with a pH of 5.6 than
on the same medium with a pH of 6.0 or higher [14].
Antifungal activity of aqueous extracts prepared
from onion was also active against Malassezia furfur,
Candida albicans, Yeasts and other Candida species
and reduced the production of aflatoxin production by
Asparguillus flavus and Asparguillus parasiticus [15].
Moreover, the Allicin had an antibacterial activity that
effect on Staphylococcus epidermidis [16]. and
methicillin-resistant Staphylococcus aureus (MRSA)
[17]. In addition, the onion had and inhibitory effect on
the main bacteria causing dental caries such
Streptococcus mutans and Streptococcus sobrinus, and
those causing adult periodontitis such Porphyromonas
gingivalis and Prevotella intermedia [18]. Zwiebelane A
which present in onion play an important role in
enhancing the potential fungicidal activity of polymyxin
B [19].
Aim of the study
This study was designed to investigate the
possible antibacterial effects of three types of onions;
red, green and white onion. Different concentration of
each onion was prepared in water extraction form.
Material and Methods:
Onions Three types of onions (Allium cepa), green
onion (var. Blanc), yellow (var. Jaune ’Espagne) and
red (var. Rouge Amposta), were selected for this
investigation.
Preparation of different types of Onion’s Extract:
An equal weight about 1Kg of each type of
onion was individually peeled and cut into small pieces,
then crushed by the domestic blender. Finally, it was
filtered by the domestic filter to obtain a final yield of
onion extract ready for antimicrobial testing.
Selected Bacterial Strains
The targeting bacteria were selected based upon
their involvement in causing common bacterial
infections in humans. In this regard, following 6
bacterial species were tested:
 Methicillin-resistant Staphylococcus aureus
(MRSA).
 Methicillin-sensitive Staphylococcus aureus
(MSSA).
 Escherichia coli (E. coli).
 Pseudomonas aeruginosa (P. aeruginosa).
 Klebsiella species (Klebsiella Spp.).
 Salmonella species (Salmonella Spp.)

Ahmed M. Kabrah et al., Sch. J. App. Med. Sci., Nov 2016; 4(11D):4128-4133
Available online at http://saspublisher.com/sjams/ 4130
In vitro Assessment of Antibacterial Effects of
different Onion extract preparations
Using filter paper method
Different concentrations of each isolated onion
extract were prepared as follow: 50 ml/L (5%), 100
ml/L (10%), 200 ml/L (20%), 400ml/L (40%), 500 ml/L
(50%), and 1000 ml (100%). The filter paper method
was used to determine the sensitivity of the bacterial
species to these different concentrations per the
inhibition zone. Each bacterial species of the above
mentioned 6 types were suspended in normal saline and
inoculated in Mueller Hinton agar. Filter papers
contained the above-mentioned onions extract, were
individually placed in each inoculated plate and then
incubated for an overnight. The results were read next
day.
Onion Pieces Method
In this method, we used Muller Hilton media
that were used in lab of King Abdul Aziz University
Hospital, the bacteria species of the above mentioned 6
types were individually inoculated in these media. The
three types of onions were individually cut.
RESULTS
Antibacterial effects of onions on Filter Paper
Method:
As shown in Table 1, the prepared green
onion didn’t affect the growth of Pseudomonas, E. coli,
and Salmonella at any tested concentration. On the
other hand, it produced bactericidal effect of MRSA,
MSSA, and Klebsiella in a concentration dependent
manner.
As shown in Table 2, the prepared red onion
didn’t affect the growth of MRSA, E. coli and
Salmonella at any tested concentration. On the other
hand, it produced bactericidal effect of Pseudomonas,
MSSA, and Klebsiella in a concentration dependent
manner.
As shown in Tables 3 the prepared white
onion produced inhibitory effect on the growth of all
tested bacteria but at various bactericidal effects
depended on its used concentration and the type of
tested bacteria.
Table 1: Showing results of filter paper method with Green onion
Bacteria
50ml\L
100ml\L
200ml\L
400 ml\L
500 ml\L
1000 ml\L
MRSA
No
No
10 mm*
12mm
14 mm
20 mm
MSSA
No
No
7mm
9mm
10 mm
12mm
E.coli
No
No
No
No
No
No
Klebsiella
No
No
8mm
9mm
11 mm
15 mm
Pseudomonas
No
No
No
No
No
No
Salmonella
No
No
No
No
No
No
* It is the diameter of the inhibitory zone.
Table 2: Showing results of filter paper method with Red onion
Bacteria
50ml\L
100ml\L
200ml\L
400 ml\L
500 ml\L
1000ml\L
MRSA
No
No
No
No
No
No
MSSA
3mm*
4mm
4mm
5mm
6mm
7mm
E.coli
No
No
No
No
No
No
Klebsiella
3mm
6mm
8mm
9mm
10mm
13mm
Pseudomonas
No
No
No
6mm
8mm
15mm
Salmonella
No
No
No
No
No
No
* It is the diameter of the inhibitory zone.
Table-3: Showing results of filter paper method with White onion
Bacteria
50ml\L
100ml\L
200ml\L
400 ml\L
500 ml\L
1000ml\L
MRSA
No
No
No
6mm*
9mm
12mm
MSSA
No
4mm
6mm
9mm
10mm
11mm
E.coli
No
8mm
12mm
15mm
25mm
40mm
Klebsiella
No
No
No
No
11mm
16mm
Pseudomonas
3mm
6mm
8mm
9mm
10mm
12mm
Salmonella
4mm
5mm
7mm
10mm
12mm
15mm
* It is the diameter of the inhibitory zone.

Ahmed M. Kabrah et al., Sch. J. App. Med. Sci., Nov 2016; 4(11D):4128-4133
Available online at http://saspublisher.com/sjams/ 4131
Antibacterial Effects of onion Pieces Method
The piece of green onion killed MRSA and
Salmonella but not MSSA, Escherichia coli, Klebsiella,
and Pseudomonas (Table 4). The piece of white onion
affected MRSA and E. coli but not MSSA, Salmonella,
Klebsiella, and Pseudomonas(Table 5) Finally, The
piece of red onion failed to inhibit the growth of
Salmonella and Klebsiella but inhibited MRSA, MSSA,
E.coli and Pseudomonas (Table 6).
Table 4: Showing the results of pieces method – Green onion-
Bacteria
Zone of inhibitory growth
MRSA
23mm*
MSSA
No
E.coli
No
Klebsiella
No
Pseudomonas
No
Salmonella
19mm
* It is the diameter of the inhibitory zone
Table 5: Showing the results of pieces method – White onion
Bacteria
Zone of inhibitory growth
MRSA
22mm*
MSSA
No
E. coli
19mm
Klebsiella
No
Pseudomonas
No
Salmonella
No
* It is the diameter of the inhibitory zone.
Table 6. Showing the results of pieces method – Red onion-
Bacteria
Zone of inhibitory growth
MRSA
22mm*
MSSA
16mm
E.coli
21mm
Klebsiella
No
Pseudomonas
12mm
Salmonella
No
* It is the diameter of the inhibitory zone
DISCUSSION
Indent this study was designed to investigate
the possible antibacterial effects of three types of
onions; red, green and white Onion. Six types of
bacteria were tested, and their selection was based upon
their common involvement in causing infectious
bacterial diseases among people who live in Saudi
Arabia.
These tested bacteria were methicillin-resistant
Staphylococcus aureus (MRSA), methicillin-sensitive
Staphylococcus aureus (MSSA), Escherichia coli (E.
coli), Pseudomonas aeruginosa (P. aeruginosa),
Klebsiella species (Klebsiella Spp.), and Salmonella
species (Salmonella Spp.)
Onion (Allium cepa L.), garlic (Allium sativum
L.) are among the oldest cultivated plants, and are used
for multiple purposes. With the increasing interest into
the utilization of natural biological active compounds
and the development of specific alternative medical
therapy we designed this study to investigate the
possible antibacterial effects of different kinds of most
commonly consumed onions. Among these numerous
and abundant naturally occurring compounds, Allium
extract has been considered a natural preservative or
food additive, and can be used as additional methods of
controlling pathogens. In addition to their nutritional
effects, the antibacterial and antifungal activities against
a variety of Gram-negative and Gram-positive were,
and continue to be extensively investigated. Onion
extract is effective in vitro against many bacteria
species including Bacillus subtilis, Salmonella, and E.
coli. Similarly, this inhibiting effect was also noted on
Staphylococcus aureus and results showed a complete
inhibition of all strains tested at a concentration of 6.5
mg/ ml. Also, the antifungal effect of onion has been
reported. Fistulosin, an antifungal compound isolated

Ahmed M. Kabrah et al., Sch. J. App. Med. Sci., Nov 2016; 4(11D):4128-4133
Available online at http://saspublisher.com/sjams/ 4132
from roots of Welsh onion exhibited marked antifungal
activities against several fungal species particularly
P.roqueforti and A.oryzae which showed high
sensitivity. The antibacterial effects of the tested onions
were documented in this study. The results showed that
the most bacteria affected with white onion were MRSA,
which showed growth reduction in the three methods,
filter paper, pieces of onion and onion extract in agar
but no effect in suspension method.
Methicillin sensitive Staphylo aureus (MSSA)
growth reduction in filter paper and onion extract in
agar methods but not pieces of onion nor suspension
methods, the white onion has affected the Escherichia
coli (E.Coli) in filter paper and pieces of onion methods
but not onion extract in agar nor suspension methods.
Klebsiella, Pseudomonas and Salmonella had showed
an effect only in filter paper method. The Green onion
had different effects with different methods, the growth
of MRSA had been reduced in filter paper and onion
extract in agar methods but not pieces of onion nor
suspension methods, then Pseudomonas, which had
been effected in onion extract in agar method but not
filter paper nor pieces of onion and suspension method,
Salmonella were reduced only in pieces of onion and
agar method. The green onion had the same effect on
MSSA and Klebsiella only in filter paper method. At
least the E. coli showed reduction only in suspension
method.
The most bacteria affected with red onion were
MSSA and Pseudomonas which showed a reduction in
filter paper, pieces and onion extract in agar methods
but not suspension method. MRSA and E. coli showed a
reduction only in two methods, pieces of onion and
onion extract in agar method for MRSA than pieces of
onion and suspension methods for E. coli. The two least
affected bacteria were Klebsiella and Salmonella that
showed a growth reduction only in filter paper and agar
method respectively.
CONCLUSION
The results of this preliminary study concluded
that:
 Extracts of three onions used have shown
antibacterial activity against the organisms
tested.
 The degree of antibacterial activity was
associated with the type of onions and
concentration of their extracts.
 Generally, onion extracts in concentrations of
50% and above have shown considerable
antibacterial activity
 Further evaluation using standardized
techniques will provide more comprehensive
information about antibacterial activities of
onions against common bacterial pathogens.
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