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Bay Leaves have Anmicrobial and Anoxidant Acvies
Sumia O Algabri1*, Basma M Doro2, Awatf M Abadi1, Mahmoud A Shiba1 and Almonder H Salem1
1Department of Pharmacognosy, University of Tripoli, Tripoli, Libya
2Department of Microbiology and Immunology, University of Tripoli, Tripoli, Libya
*Corresponding author: Algabri SO, Department of Pharmacognosy, Faculty of Pharmacy, University of Tripoli, Tripoli, Libya, Tel:
+218928629603; E-mail: mannaaljabri@yahoo.com
Received date: July 06, 2018; Accepted date: July 28, 2018; Published date: August 02, 2018
Copyright: © 2018 Algabri SO, et al. This is an open-access arcle distributed under the terms of the creave Commons Aribuon License,
which permits unrestricted use, distribuon and reproducon in any medium, provided the original author and source are credited.
Citaon: Algabri SO, Doro BM, Abadi AM, Shiba MA, Salem AH (2018) Bay Leaves have Anmicrobial and Anoxidant Acvies. J Pathogen Res
Vol.1 No.1:3.
Abstract
Background: Bay, Laurus nobilis L is a nave plant and is
one of the most frequently used cooking spices. The dry
Bay leaves are used to treat several digesve problems
with anconvulsive, narcoc and anbacterial properes.
Thus, this study was aimed to invesgate the in-vitro
anmicrobial and anoxidant acvies of dierent
extracts of Bay leaves.
Methods: The dried Bay leaves were extracted
sequenally with n-hexane, dichloromethane and
methanol by Soxhlet apparatus. The extracts were
concentrated and evaluated for anmicrobial acvity
against Staphylococcus aureus, Pseudomonas aeroginosa,
E. coli and Candida albicans using well diusion method
to determine the diameter of zone of inhibion. Also, Bay
leaves extracts were evaluated for anoxidant acvity
using qualitave DPPH assay.
Results: The ndings of anmicrobial assay showed that
methanolic extract of Bay leaves has an anbacterial
acvity against Staphylococcus aureus with zone of
inhibion of 18 ± 0.8 mm, which is higher than phenol
inhibion zone (10 ± 1.0 mm) whereas, no anbacterial
inhibion against other tested bacteria was detected. The
dichloromethane extracts inhibited E. coli growth with
zone of inhibion of 14 ± 0.6 mm and with Staphylococcus
aureus of 18 ± 0.8 mm, while, the n-hexane extract has no
anbacterial acvity with all of the tested organisms.
However, all of Bay leaves extracts displayed no anfungal
eect on Candida albicans. In terms of anoxidant
acvity, all of Bay leaves extracts exhibited anoxidant
acvity, but the methanolic extract displayed the most
prominent level.
Conclusion: The bay leaves extracts have anbacterial and
anoxidant acvity and further invesgaons to assess
these eects are recommended.
Keywords: Bay leaves; Staphylococcus; Qualitave DPPH;
Anmicrobial; Anoxidant
Introducon
One of the most well-known plants from the Lauraceae
family is Laurus nobilis L, which is also known as Bay or laurel
leaves. Bay is one of the most frequently used cooking spices
for avouring meat products, shes and soups. It is a nave
plant in the Southern Mediterranean area, found in warm
climate regions, but it is used as a decorave plant in Europe
and USA. In addion, it is commercially grown in, Algeria,
Morocco, Portugal, Spain, Italy, France, Turkey and Mexico
[1-3].
Tradionally, the dry Bay leaves and their infusions are used
to treat digesve dicules as epigastric pain, atulence,
bloang, and eructaon problems. Leaves and fruits of Bay
plant have been used as astringent, diaphorec, smulant and
emec as well as emmenagogue, aborfacient and insect
repellent. In addion, as it is an aromac plant, its essenal oil
is added in the cosmec products like soaps, creams and
perfumes [4].
Phytochemical studies on Bay leaves and its fruits have
indicated various secondary metabolites including alkaloids,
avonols (kaempferol, myricen, and quercin), avones
(apigenin and luteolin), glycosylated avonoids, sesquiterpene
lactones, monoterpene and germacrane alcohols [5-10].
Interesngly, there is a worldwide concern around that use
of anbiocs to treat bacterial and fungal infecons can lead
to the rise and spread of organisms resistant to broad-
spectrum anbiocs, opening ways to use plants as natural
sources for novel anmicrobial agents with a similar acvity
[11-13]. Natural medicinal plants, as L. nobilis, are rich sources
of bioacve compounds. Thus, the biological properes of Bay
extracts and its essenal oil are documented, specically their
anmicrobial, anfungal and anoxidant eect. A previous
study has reported that the aqueous decocon of bay leaf
showed 53.4% of bactericidal eect against 176 bacterial
isolates belonging to 12 dierent genera of bacterial
Research Article
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2018
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populaon isolated from oral cavity of 200 individuals [14].
Also, another study found that the bay leaf essenal oil (EO)
was able to decrease the populaon of total coliforms (2.8 log
CFU/g) and to prolong the shelf life of fresh Tuscan sausage
stored at 7°C for 14 days for two days [15]. In a Turkish
research, the in vitro anbacterial against three Gram-posive
(Bacillus sublis, Staphylococcus aureus and S. epidermidis)
and two Gram-negave bacteria (Escherichia coli and
Pseudomonas aeruginosa), using agar diluon methods was
assayed. Furthermore, its potenal toxicity to Candida albicans
and Aspergillus niger was examined by using both disc-
diusion and agar diluon methods. The ndings of this study
showed the minimum inhibion concentraon (MIC) of the L.
nobilis extract was 5 mg/mL for all the bacteria tested. Also,
the extract of L. nobilis, showed higher inhibitory acvity
against the yeast C. albicans and the fungus A. niger than the
standard anfungal nystan that used as a posive control
[16].
In addion, the potenal anoxidant eect bay leaves
extract has been reported. The methanolic extract of seed oil
exhibited anoxidant properes in both 2, 2-diphenyl-l-
picrylhydrazyl (DPPH) free radical scavenging and β-carotene/
linoleic acid test systems [17]. In another study, the
anoxidant possibility of ethanolic and aqueous extracts of
Hypericum perforatum, Ocimum basilicum and L. nobilis leaves
were assessed by DPPH assay. The aqueous extract of L. nobilis
showed the lowest radical scavenging capacity (RSC) as
compared to H. perforatum and O. basilicum. However, the
ethanolic extracts of L. nobilis showed more DPPH radical
scavenging eect than their aqueous extracts [18].
As in Libya the bay leaves commonly used in tradion meals,
the aim of this study was to explore the in-vitro anmicrobial
and anoxidant acvies of dierent extracts of Bay leaves
collected from local Libyan store.
Materials and Methods
Chemicals and reagents
2,2 diphenyl -1- picryl hydrazyl (DPPH) and ascorbic acid
(Vitamin C) were obtained from Sigma Aldrich (Germany),
Silica gel F254 TLC plates was obtained from Merck (Germany),
metathanol (MeOH), dichloromethane (DCM) and hexane are
of HPLC grade and obtained for Fisher Scienc.
Plant material
The dried Bay leaves were obtained from local market in
Tripoli, Libya, in 27 November 2014 ready for grinding and
extracon. The plant was idened and authencated as
Laurus nobilis. Dried leaves by Botanists in the Herbarium of
Sciences College, University of Tripoli, Libya where a voucher
specimen was deposited.
Preparaon of plant extracts
The dried Bay leaves were nely ground using a coee
grinder and 196 gm were placed in a cellulose thimble and
extracted with a Soxhlet apparatus sequenally with n-hexane,
dichloromethane (DCM) and methanol (MeOH) extracts were
concentrated using a rotary evaporator at 45°C and stored in
pre-weighed glass jars for further analysis.
Evaluaon of anmicrobial acvity
The anmicrobial acvity of Bay leaves extracts was tested
in vitro using the agar well-diusion assay. This method was
performed using freshly prepared Mueller Hinton agar
inoculated with an overnight culture of bacteria suspended in
sterile saline and adjusted to a 0.5 McFarland standard. Aer
solidicaon, 6 mm diameter wells were punched into the
Mueller Hinton agar plates [19]. Each well was lled with 100
μl of the extract soluon at concentraon 1 mg/ml and then
incubated for 24 h at 37°C. The inhibion zones were
measured in millimeters. 5% phenol was used as a standard.
The controls were prepared without extract. The experiment
was carried out in triplicate to ensure reproducible results.
Dimethylsulfoxide (DMSO) was used as a negave control
while phenol was used as a posive control.
Bacterial strains and media
The anmicrobial acvity of Bay leaves extracts was tested
against two Gram-negave bacteria Pseudomonas aeruginosa
(ATCC 29138) and Escherichia coli (ATCC 25922), and one
Gram- posive bacteria Staphylococcus aureus (ATCC 29213).
In addion, the same extracts were tested against the yeast
Candida albicans (ATCC 10231). The standard bacterial strains
were streaked onto nutrient agar, incubated for 24 hours at
37°C then stored at 4°C. The media used in this study were
nutrient broth (NB), nutrient agar (NA) and Mueller Hilton agar
(Oxoid). The media was prepared according to the
manufacturer’s instrucons.
Evaluaon of anoxidant acvity
Qualitave DPPH assay: Anoxidant acvity of dried Bay
leaves extracts was analyzed qualitavely by using 2,
2,diphenyl-1-picrylhydrazyl (DPPH) assay on thin layer
chromatography (TLC) plates [20]. DPPH assay was used as a
screening test for the radical scavenging ability of the
compounds present in dierent extracts of Bay leaves. Silica
gel F254 TLC plates were used to separate Bay leaves extracts
where 10 μl aliquots of each of the n-hexane, DCM and MeOH
extracts (10 mg/ml) were applied to Silica gel plates using
capillary tubes, le to dry, then; The plates were dried in the
fume hood for the detecon of anoxidant acvity,
chromatograms were sprayed with 0.2% DPPH in methanol, as
an indicator. It was allowed to develop for 30 min. The
presence of anoxidant compounds was detected by
observaon of yellow spots against a purple background on
TLC plates sprayed with 0.2% DPPH in methanol. Vitamin C (2
mg/100 ml methanol) was used as a posive standard [20,21].
Journal of Pathogen Research
Vol.1 No.1:3
2018
2This article is available from: http://www.imedpub.com/journal-pathogen-research/inpress.php
Results and Discussion
Anmicrobial acvity
In Table 1, the anmicrobial acvity of Bay leaves in terms
of zone of inhibion (in mm diameter) of n-hexane,
dichloromethane and methanolic extracts at concentraons
0.5 mg/ml against the tested microorganisms were shown. The
ndings indicated that the methanolic extract of Bay leaves
has an anbacterial acvity against Staphylococcus aureus
with zone of inhibion 18 ± 0.8 mm, which is much higher than
the posive control (phenol) inhibion zone (10 ± 1.0 mm),
whereas, there was no anbacterial inhibion against other
tested bacteria. The Dichloromethane extract inhibited E. coli
growth with an inhibion 14 ± 0.6 mm and Staphylococcus
aureus with 13 ± 0.5 mm, while the n-hexane extract has no
anbacterial acvity with all the tested organisms. However,
all of Bay leaves extracts displayed no anfungal eect on
Candida albicans (Table 1).
Table 1 Average diameter, in millimeters, of the bacterial inhibion zones of Bay leaves extracts at concentraon 0.5 mg per ml
against tested microorganism.
Microorganism Mean diameter of zone of inhibition (mm ± SE)
Extract (0.5 mg/ml)
n-hexane extract DCM Extract MeOH Extract 5% Phenol
Staphylococcus aureus 0.0 ± 0.0 13 ± 0.5* 18 ± 0.8* 10 ± 1.0
Pseudomonas aeruginosa 0.0 ± 0.0 0.0 ± 0.0 0.0 ± 0.0 27 ± 0.5
E. coli 0.0 ± 0.0 14 ± 0.6 0.0 ± 0.0 12 ± 2.0
Candida albicans 0.0 ± 0.0 0.0 ± 0.0 0.0 ± 0.0 11 ± 2.5
*Statistically significant difference by t-test.
In a previous study, the in vitro anmicrobial and
anoxidant acvies of the essenal oil, seed oil and
methanolic extract of seed oil of Bay leaves were showed that
the extract of seed oil has more eecve anbacterial acvity
compared with essenal oil and seed oil [22]. Furthermore,
GC-MS analysis of essenal oil resulted in idencaon of 25
compounds. 1.8-Cineol (44.72%), a-Terpinyl acetate (12.95%),
Sabinene (12.82%) were the main components. In addion,
other study reported that Laurus nobilis extract has
anbacterial acvity against Staphylococcus aureus where the
zone diameter of inhibion of Laurus nobilis extract was
comparable to zone diameter of the inhibion of tetracycline
[23]. That may support the ndings of this study in terms of
the anbacterial eect.
Anoxidant acvity
Qualitave DPPH assay: Various methods have been used
to evaluate anoxidant capacity of some compounds in
dierent plant extracts, one of the most widely used methods
are those involve the generaon of free radicals which then
neutralized by anoxidant compounds [24]. The DPPH
anoxidant assay is based on the ability of DPPH to decolorize
in the presence of anoxidants. The odd electron in the DPPH
radical is responsible for the deep purple color. When DPPH
accept an electron from anoxidant compound, the DPPH
decolorize [20].
In the present study, only TLC based qualitave DPPH assay
was performed to evaluate anoxidant acvity of bay leaves
extracts which provide a rapid, exible and ecient screening
method for anoxidant acvity [25]. The results showed the
presence of anoxidant acvity in all the tested Bay leaves
extracts as it is given in Figure 1. The acvity was indicated by
the presence of yellow spots against a purple background on
the chromatograms. The degree of acvity of all the samples
tested was also determined qualitavely from observaon of
the yellow color intensity. It is observed that methanolic
extract of Bay leaves displayed the most prominent level of
anoxidant acvity where it has an intense yellow color
compared with the control using vitamin C.
Figure 1 Chromatogram of Bay leaves extracts sprayed with
0.2% DPPH in methanol yellow zones indicate anoxidant
acvity.
Several previous studies assessed the quantave
anoxidant acvity of dierent extracts of Bay leaves by using
dierent models, all of them indicated that Bay leaves extracts
provide both In vitro and In vivo anoxidant eect [26-30].
Although, in this research only the qualitave anoxidant
eect was tested, and this eect may be related to the
presence of phenolic secondary metabolites like phenols.
Conclusion
The ndings of this study show that the bay leaves extracts
have anbacterial and anoxidant eects. However,
Journal of Pathogen Research
Vol.1 No.1:3
2018
© Copyright iMedPub 3
quantave DPPH assay is needed to conrm the obtained
results and more invesgaons on wide range of pathogen to
assess the spectrum of bay leaves extracts are recommended.
Acknowledgements
The authors would like to thank Prof. Fathi M Sherif,
Department of Pharmacology, for his help in crical reviewing
the manuscript and valuable comments. Also, thanks go to the
laboratory sta of Microbiology and Immunology for their
help.
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