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3173 International Journal of Medical Science and Clinical Invention, vol. 4, Issue 8, August, 2017
International Journal of Medical Science and Clinical Inventions 4(8): 3173-3177, 2017
DOI:10.18535/ijmsci/v4i8.12 ICV 2015: 52.82
e-ISSN:2348-991X, p-ISSN: 2454-9576
© 2017,IJMSCI
Original Research
Antimicrobial Activity of Coconut Oil and its Derivative (Lauric Acid) on Some
Selected Clinical Isolates
*Abbas, Abel Anzaku1; Ernest Bassey Assikong2; Akeh,Martins1; Upla, Peter1; Tuluma, Terungwa
Keneth3.
1 Department of Microbiology, Federal University Lafia, Nigeria.
2 Associate Professor , Department of Microbiology, University of Calabar, Nigeria.
3Department of Microbiology, School of Nursing and Midwifery Makurdi, Benue State, Nigeria
Abstract: This study investigates the in vitro antimicrobial activity of coconut oil and its fatty acid( lauric acid) on selected
clinical isolates. Clinical isolates were obtained from the General Hospital Maitama, Abuja, Nigeria. Media preparation and
biochemical examination of the organisms were done according to standard methods. Organisms used were
StaphylococcusaureusStreptococcus species, Lactobacillus species and Escherichia coli. Coconut oil was extracted through
fermentation method were as lauric acids was esterified from coconut oil through freezing and were subjected to sterility test.
Bauer-Kirby disc diffusion assay was used for the sensitivity assessment. Zones of inhibition were measured in diametre. Coconut
oil showed resistant on the isolates at the various dilution concentrations. Lauric acid demonstrated significantly appreciable antim
icrobial effect on the test organisms with the highest zone of inhibition on Staphylococcus aureus (10.50)mm, Streptococcus speci
es (10.00) mm, Lactobacillus species (10.00) mm and the lowest inhibition on Escherichia coli (4.00)mm even at the Minimum
Inhibitory Concentration (MIC).Escherichia coli which showed relatively low zone of inhibition even at the highest dilution
concentration. The acid generally demonstrated appreciable sensitivity on the isolates with low effect on E. coli compare to other
strains. This study recommends the use of coconut oil as therapeutic agent as well as in fighting antibiotic resistant since it
contains lauric acid which is bactericidal. Further studies should be done on the oil and its derivative both in vitro and in vivo
unveils its mechanisms of actions.
Keywords: Antimicrobial activity, coconut oil, lauric acid, clinical isolates.
INTRODUCTION
Plants of medicinal importance containhuge varieties of
phytochemicals with important therapeutic properties that can
be used in the treatment of emerging and re-emerging
diseases. Consequently, there is the increasingly justified
assumption which claims that traditional medicine is cheaper
and more effective than modern medicine. The studies of
medicinal plants used as folklore remedies have therefore
attracted immense attention in the scientific world in an
attempt to find possible solutions to the problems of multiple
resistances to the existing synthetic and conventional
antimicrobials (Taiwoet’ al., 2011). The discovery of
antibiotics had eradicated the infections that once ravaged the
humankind, but their indiscriminate use has led to the
development of multidrug-resistant pathogens (Shanmuganet’
al., 2008).
Coconuts are an underutilized food with a hidden wealth of
nutritional value for the body. The fat content plays into the
mass confusion surrounding healthy and unhealthy fats, but
there are a surprising number of benefits with this unusual nut
as it provides a very unique type of oil, made of several
ingredients including medium chain fatty acids, lauric acid and
saturated fat (Schlievert,et’ al., 2008). It is semi-solid at room
temperature as a soft, almost waxy substance. Coconut oil is
prized for its health-giving properties, considered one of the
beneficial oils to use when cooking. Coconut oil is stable in
high heat while many other oils are damaged upon heating,
making them very unhealthy for cooking. Over the past
several years, nutritional advice has focused on the avoidance
of fat, particularly saturated fat. We are now learning, or
relearning, what many cultures have known for centuries.
Healthy fats can include some saturated fat. The quality of
animal fats will depend on the health of the animal. We are
also learning that many vegetable oils that were once
considered healthy are known to become damaged with heat.
One of the amazing qualities of coconut oil is its antibacterial
properties. Monolaurin, an ingredient in coconut oil, has long
been recognized for its bug-fighting properties. It is found in
breast milk, perhaps in part to help protect the developing
baby from infection (Clarke and May, 2007). It appears that
coconut milk can protect against several different kinds of
bacteria and fungi of clinical impact and can further benefit
Abbas, Abel Anzaku et.al / Antimicrobial Activity of Coconut Oil and its Derivative (Lauric Acid) on Some Selected
Clinical Isolates
3174 International Journal of Medical Science and Clinical Invention, vol. 4, Issue 8, August, 2017
the skin by treating and preventing skin infections (Carpo et’
al., 2007; Clarke and May, 2007). According to Abbas et’ al.
(2017), this virgin coconut oil which is a potent nondrug or
natural yeast fighter, contains three medium chain fatty acids,
i.e., lauric acid (50–53%), caprylic acid, and capric acid, all of
which have antibacterial and antifungal effect against lipid
coated bacteria such as staphylococcus species and fungi such
as Candida spp.
Lauric acid a twelve (12) carbon chain acids, is one of the
medium chain fatty acids gotten from some plants oil
particularly coconut oil and others related oil such as palm
kernel oil which has been known as one of the most active
ingredient and is more predominant in the total saturated fat
present (Bruce, 2000).This acid is found in many vegetables,
fats particularly in coconut oil and palm kernel oil (Chuah et’
al., 2014); and has been known as one of the most active
ingredient and composed over 52% of the total 92% saturated
fats present in the coconut oil and is claimed to play a
significant role in the healing miracle that is revealed in
coconut oil (Fife, 2003). Medium-chain free fatty acids which
lauric acid fall under have been found to have a broad
spectrum of microbicidal activity though the mechanisms by
which the lipids kill bacteria is not known, but electron
microscope studies indicate that they disrupt cell
membranes(Ogbolu, 2007). On the other hand, Free Fatty
Acids (FFA) of various chain lengths (C8- C18) have
antibacterial activity against a range of Gram-positive
bacteria, but not against a number of Gram-negative bacteria
Georgel et al., 2005;Skrivanova et al., 2005;Drake et al.,
2008). Variations in composition of plant and genetic disparity
among bacteria and fungi of the same or different species have
been found to be responsible for the few inconsistencies in the
antibacterial and antifungal properties of plant extract. The
esterification of coconut oil which yielded a carbon chain has
proved beyond reasonable doubt that, lauric acid 12-carbon
chain fatty acid is more biological active and has the highest
antiviral activities than coconut oil which is the parent
substance (Kabara, 1960). This resulted from the Medium
Chain Triglycerides (MCTs) present in coconut oil which anti-
bacterial influence because it has the ability to disintegrate
bacterial cell walls; MCTs are also presenting the ability to
treat severe bacterial infections that are antibiotic resistant
(Bruce, 2000). Despite the vast impact of coconut plants as a
whole and its health importance to humanity hitherto, most
people still lack the basic knowledge in this plants and
relatively few studies has been done to ascertain its health
impact.In this study, antimicrobial activity of coconut oil and
its derivative (lauric acid) were investigated.
TERIALS AND METHODS
Preparation of coconut oil
Fresh coconut (Cocos nucifera) was obtained from Lafia
modern market Lafia, Nigeria. The fresh coconut meat was
grated and pressed using a sterilized sieve to produce coconut
milk, which was further allowed to ferment for 48 hours under
anaerobic condition (Abbas et’ al., 2017). After the
fermentation, three layers were formed: the water layer, lipid
layer and the protein coat layer. Protein coat and the water
layer were separated from the oil (lipid layer). The oil was
then heated slightly to remove remaining moisture. After
which the oil was filtered by passage through a 25m-pore size
filter (Millipore, St. Quentin, France) to give an aqueous
extract of coconut oil. This was collected in a sterile vial and
stored at 4°C until use.
Preparation of lauric acid
Extra virgin coconut oil was poured into a temperature glass
container, manufacturer filter to remove impurities, digital
freezer was set at 25.1oC 3 to freeze coconut oil and lauric
acid was extracted at 47o C (Abbas et’ al., 2017).
Suspension of test organisms
Suspension of each of the test organisms was made by
collecting a loopful of colony from each plate and was
incubated overnight at 37°C in Nutrient broth. The overnight
broth culture of organisms was diluted in nutrient broth to an
inoculum load of approximately 1x106 cfu/ml. It was
standardized according to National Committee for Clinical
Laboratory Standards (NCCLS, 2002) by gradually adding
normal saline to compare its turbidity to McFarland turbidity
standard of 0.5 which is approximately 1.0 × 106 cfu/ml.
Sterile swab sticks were dipped into each of the bacterial
solution and were used to inoculate the solidified Nutrient agar
plates ensuring that the plates were completely covered for
uniform growth as described by (Aboh et al., 2013).
Sterility test
Pure virgin coconut oil and the extracted lauric acid were
cultured differently on prepared media plates and incubated
overnight at 4°C. This was done to ensure that the extracts
were completely sterile. All media prepared were picked at
random and incubated overnight at 37°C for the purpose of the
study.
Antimicrobial susceptibility test
Antimicrobial susceptibility test was carried out in each of the
plate using agar disc diffusion method as described by Bauer-
Kirby (2008).This involves a heavy inoculation of an agar
plate with the test organisms. A disc of filter paper (Whatman
filter paper) was impregnated with a known volume and
appropriate concentration of lauric acid and was placed on a
plate of susceptibility testing agar uniformly inoculated with
the test organism and equally spaced on the inoculated plate.
The antimicrobial agent diffused from the disc into the
medium and the growth of the test organism was inhibited at a
distance from the disc that is related (among other factors) to
the susceptibility of the organisms. Strains susceptible to the
antimicrobial were inhibited at a distance from the disc
whereas resistant strains have smaller zones of inhibition or
grow up to edge of the disc (Cheesbrough, 2006). Following
incubation, the agar plate was examined for zones of
Abbas, Abel Anzaku et.al / Antimicrobial Activity of Coconut Oil and its Derivative (Lauric Acid) on Some Selected
Clinical Isolates
3175 International Journal of Medical Science and Clinical Invention, vol. 4, Issue 8, August, 2017
inhibition (areas of no growth) surrounding the discs. Zone of
inhibition indicates antimicrobial activity against the
organisms. Absence of zone of inhibition indicates that the
acid was ineffective against the test organisms or the
organisms are resistant to the acid.
RESULT AND DISCUSSION
Result of the morphological identification, biochemical
reaction, carbohydrate utilization and haemolytic reaction of
the test organisms is shown in table 1 below.
Table 1:Biochemical identification and carbohydrate
utilization of the isolates
Biochemic
al
examinatio
n
Staphyloco
ccus ureus
Streptococ
cus species
Lactobacil
lus species
Escheric
hia coli
Catalase
+
-
-
+
Oxidase
-
-
-
-
Coagulase
+
-
-
-
Motility
-
-
-
+
Indole
-
-
-
+
Methyl Red
+
+
-
+
V. P
+
+
-
-
Urease
+
-
-
-
Glucose
+
+
-
+
Sucrose
+
+
-
+
Mannose
+
+
-
-
Mannitol
Lactose
+
+
-
+
-
+
+
-
Haemolysis
Acid fast
stain
+
-
+
-
-
+
-
-
Keys: + = Positive; - = Negative; VP = Voges Proskauer
The result of the agar disc diffusion antimicrobial assay of
coconut oil on the selected clinical isolates is shown in table 2
below. The clinical isolates used for the sensitivity assay
were: Staphylococcus aureus, Streptococcus
species,Escherichia coliand Lactobacillusspecies showing
resistance to the oil extract.
Table 2: Sensitivity assay of coconut oil on the isolates
BACTERIAL
ISOLATES
30%
50%
70%
100%
S. aureus
R
R
R
R
Streptococcus
R
R
R
R
E. coli
R
R
R
R
Lactobacillus
R
R
R
R
R = Resistance of isolates to the oil extract, % =
percentage of the dilution concentration
The result of the agar disc diffusion antimicrobial assay of
coconut oil on the selected clinical isolates is shown in table 2
below. The clinical isolates used for the sensitivity assay
were: Staphylococcus aureus, Streptococcus, Escherichia
coliand Lactobacillus the zones of inhibition observed were
recorded accordingly.
Table 3: Sensitivity assay of coconut oil on the isolates
Table 4 below is the presentation of the result of Minimum
Inhibitory Concentration (MIC) of lauric acid sensitivity on
the isolates at various dilution concentrations.
Table 4: Minimum Inhibitory Concentration (MIC)
In this study, both coconut oil and its fatty acid (Lauric acid)
were for their antimicrobial properties on a few selected
clinical isolates. Organisms isolated were Staphylococcus
aureus, Streptococcus, Escherichia coliand Lactobacillus
species. Both organisms showed resistance to coconut oil at
the variousdilutionconcentrations as opposed to the study of
Ogbolu et’ al.(2007), who reported the antimicrobial potential
of coconut oil on fungal organisms. The method employed by
Ogbolu et’ al. (2007) differed from this study because coconut
oil was diluted with 1% ethanol which earlier knowledge has
educated us on the antimicrobial properties of all classes of
alcohol in which ethanol is included. The diluent could be
responsible for the inhibitory effect exerted in the study.
Lauric acid in this study showed considerable inhibitory effect
on virtually all the clinical isolates used in this studywith
decrease in effects corresponding to the concentration of the
acid. The acid demonstrated highest zones of inhibition on the
isolates with the following diametre: Staphylococcus aureus
(10.50)mm, Streptococcus species (10.00)mm Lactobacillus
BACTERIAL
STRAINS
Susceptibility at giving concentration
100% 70% 50%
30%
Staphylococcus
aureus
10.50
9.00
8.50
7.50
Streptococci
Escherichia coli
Lactobacilli
10.00
4.00
10.00
9.00
3.00
9.50
8.50
2.00
10.00
7.00
1.50
8.00
% = Percentage
Abbas, Abel Anzaku et.al / Antimicrobial Activity of Coconut Oil and its Derivative (Lauric Acid) on Some Selected
Clinical Isolates
3176 International Journal of Medical Science and Clinical Invention, vol. 4, Issue 8, August, 2017
species (10.00)mm whereas the lowest inhibitory effect was
observed on Escherichia coli(4.00)mm at the same dilution
concentration. In general the acid was more effective against
Staphylococcus aureus,Streptococci, and Lactobacillieven at
the lowestdilution concentration whereas E. coli which is a
Gram negative bacterium showed relatively low
inhibition.Similarly Abbas et’ al. (2016), reported that
Synthetic sodium laurate (lauric acid) fatty acid exhibit
significantly high antimicrobial activity by inhibiting
microbial survival and biofilm growth against Streptococcus
mutans. Arguably, Padgett et’ al. (2000), reported that high
level of lauric acid addition (8%) significantly lower the film
water permeability. This result conforms to the popular
assertion that says the higher the concentration, the higher the
antimicrobial effect of agent against organisms (Rutala et al.,
2008). Escherichia coliwhich is Gram negative bacteria
showed very low inhibitory effect to the acid tested at a lower
concentration compare to other Gram positive bacteria such as
S. aureus, Streptococci and Lactobacilli. This finding
obeysthe findings of Mamman et al. (2005) that says Gram
negative bacteria exhibit much resistance compare to Gram
positive bacteria. Lauric acid exhibited appreciably high
antimicrobial activity in some clinical isolates than others and
the zones of inhibition varied based on their dilution
concentration declining as the dilution concentration
decreases.
CONCLUSION AND RECOMMENDATION
This study argued the earlier acclamation that says coconut oil
has antimicrobial activity in vitro and further affirmedthat,
lauric acid has antibacterial effect on Gram positive bacteria
more compare to Gram negative bacteria. This however
recommends use of lauric acid in treating some of the
emerging and re-emerging diseases as well as improving
health status. More studies should be done to ascertain the
mechanisms of actions of this acid on microorganism
generally and their susceptibility pattern.
Declarations
Authors’ contributions
AAA is the main author and was responsible for the writing of
the manuscript, participated in data collection and
interpretation as well as drafting and review of the manuscript.
UP was involved in the study design and data interpretation.
EBEA and TTK reviewed the manuscript. Both authors read
and approved the final manuscript.
Ethical consideration
This research does not required ethical clearance as human
participants were not involved in the study; however, proper
permission was taken to obtain clinical isolates for the purpose
of the study.
Competing interests
There is no competing interest in the publication of the journal
by authors.
Availability of data and materials: The datasets used and
analyzed during this study are available from the corresponding
author on reasonable request.
Funding
This study did not receive any funding from anywhere.
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