Potential Antimicrobial Activity of Various Extracts of Bacopa
The present study was carried out to evaluate the antimicrobial
potential of ethanolic, diethyl ether, ethyl acetate and aqueous extracts
of aerial parts of Bacopa monnieri (L.). The antimicrobial activity
of ethanolic, diethyl ether, ethyl acetate tested for the Staphylococcus
aureus, Proteus vulgaris, Candida albicans and Aspergillus
niger. Diethyl ether extracts of Bacopa monnieri showed an
antibacterial activity against gram positive and ethyl acetate extract
was active against gram negative organism. The extract of diethyl ether
having potent antimicrobial activity against Staphylococcus aureus
at higher concentrations (300 μg mL-1). Ethanolic extract
of Bacopa monnieri has more antifungal activity against Candida
albicans and Aspergillus niger. Diethyl ether extract and Ethyl
acetate extract has slight antifungal activity but have broad spectrum
of antibacterial effect against the entire tested organisms, whereas ethanolic
extract showed marked inhibitory activity against fungal species. Aqueous
extract of the different concentration showed no inhibitory effects on
the tested microorganisms due to loss of some active compounds during
extraction processes of the sample.
The medicinal properties of several herbal plants have been documented
in ancient Indian literature and the preparations have been found to be
effective in the treatment of diseases. Therefore to meet the increasing
demand of manufacturing modern medicines and export, the need of the medicinal
plants have enormously increased. This demand is generally met with by
cultivating and uprooting medicinal plants (Singh and Dhawan, 1997).
During the last 10 years pace of development of new antimicrobial drugs
has slowed down while the prevalence of resistance has increased astronomically
(Akinpelu and Onakoya, 2006). The problem of microbial resistance of growing
and the outlook for the use of antimicrobial drugs in the future is still
uncertain. Therefore, actions must be taken to reduce this problem, such
as controlling the use of antibiotics and carrying out research for the
better understanding of the genetic mechanism of resistance. This prompted
us to evaluate plants as the source of potential chemo therapeutic agent,
antimicrobial agent and their ethno medicinal use (Prashanth et al.,
S. aureus infections can be spread through contact with pus from
an infected wound, skin to skin contact with an infected person by producing
hyaluronidase that destroy tissues. Proteus vulgaris can cause
many different types of infection to humans such as urinary track infection,
wound infections. Proteus vulgaris can be deadly when in the sinus
or respiratory tissues, if left untreated or is treated with antibiotics
that have only an intermediate effect on Proteus vulgaris (Partrick
et al., 1998). Candida albicans becomes an infectious agent
when there is some change in the body environment that allows it to grow
out of control. Most of the time, Candida infections of the mouth, skin,
or vagina occur for no apparent reason. Among fungal pathogens Candida
albicans is known to cause serious systemic infections including opportunistic
infection in patients infected with HIV virus (Srinivasan et al.,
2001). Aspergillosis is a large spectrum of diseases caused by members
of the genus Aspergillus (Stevens et al., 2000). Aspergillus
spp. are frequently secondary opportunistic pathogens in patients with
bronchiectasis, carcinoma, other mycoses, sarcoid and tuberculosis (Fujimura
et al., 1998).
Bacopa monnieri, also referred to as Herpestis monniera, water
hyssop. The name Brahmi has been used in the Ayurvedic system of medicine
for centuries (Mukherjee and Dey, 1966). Bacopa monnieri, a member
of Scrophulasiaceae family, is a small, creeping herb with numerous branches,
small long leaves and produces light purple or white colour flowers (Bone,
1996). The purpose of the present study was to evaluate the anti microbial
activities of various extracts of Bacopa monnieri.
MATERIALS AND METHODS
Collection of plant sample: Bacopa monnieri plant material
was collected from Pondicherry University, Pondicherry, India during December
2007. The Aerial parts of plant materials were shade dried and powdered.
Extraction: Approximately 75 g of the sample was taken and extracted
using Soxhlet apparatus(Alade and Irobi, 1993) with ethanol and ethyl
acetate for approximately 6-8 h. The extracts were vacuum evaporated,
dried and stored. The leaf powder was cold extracted with 50% diethyl
ether with occasional stirring and kept as such for 24 h. The pooled extracts
were concentrated and evaporated to dryness under pressure (Kumar et
al., 1998). The leaf powder was mixed with 200 mL of distilled water
and boiled. Filtered through of Whatmann No. 40 filter paper and taken
to dryness to obtain the extract (Seema et al., 1996).
Antibacterial sensitivity test: The plant extracts were tested
for anti bacterial activity by the well diffusion method using bacterial
strains, Staphylococcus aureus and Proteus vulgaris. Antibacterial
activity was expressed as the ratio of the inhibition zone (mm) produced
by the plant extract.
Antifungal sensitivity test: The extracts thus prepared were tested
separately for their fungal toxicity against Aspergillus niger
and Candida albicans. The leaf extracts were added separately to
the cooled sabourauds dextrose agar medium to give the concentrations
of 0.1, 0.2 and 0.3 mL. The amended SDS medium was dispersed in Petri
plates and allowed to solidify. After solidification 10 mm agar block
cut from the actively growing margin of the pathogen viz., Aspergillus
niger and Candida albicans were inoculated at the centre of
the plates. The plates were incubated at 30°C for 7-14 days. The radial
growth was measured periodically and the mean growth rate was calculated.
Control was maintained.
The problem posed by the high cost, adulteration and increasing side
effects of synthetic drugs coupled with their inadequacy in diseases treatment
found more effective especially in the developing country cannot be over
emphasized (Shariff, 2001).
Diethyl ether extract of Bacopa monnieri have maximum (18.00±1.00
mm) inhibitory effect against Staphylococcus aureus at a concentration
of 300 μg. Ethyl acetate and ethanolic extract has the moderate effect
over Staphylococcus aureus (Table 1). The
aqueous extract does not show any inhibitory effect. Table
1 presents the inhibitory effects of various extracts of Bacopa
monnieri against Proteus vulgaris. This reveals the potency
(15.00±1.73 mm) of ethyl acetate at 300 μg. Ethanolic and
diethyl ether extract showed lesser inhibitory effect when compared with
ethyl acetate extract. Table 1 also denotes the antifungal
ability of various extracts of Bacopa monnieri against Candida
albicans and Aspergillus niger. Ethanolic extract was found
to have maximum activity (11.00±1.00 and 11.67±0.57 mm,
respectively) followed by diethyl ether extract. Aqueous extract of Bacopa
monnieri does not show any inhibitory effect against the organisms
||Inhibitory effect of various extracts of Bacopa monnieri
(Linn.) against pathogenic organisms
|*Inhibition zones excluding well: mean±SD, n
= 3 (three replicates), NA→No. Activity found at this
The results showed that all the extracts of Bacopa monnieri (aerial
part) possessed antimicrobial activity except aqueous extract. The growth
of Staphylococcus aureus was inhibited successfully by diethyl
ether extract at higher concentration at 300 μg. It is clear that
ethyl acetate and diethyl ether have antibacterial activity against the
tested bacterial species.
On the other hand ethanolic extract, exhibited an elevated antifungal
activity against both the fungal species. Antimicrobial activity from
plant source can be assumed to be useful. The extracts produce anti-infective
agent, which could be active against human pathogens(Prashanthkumar et
al., 2006). Apart from antimicrobial activity exhibited by tannins,
they also lead with proteins to provide the typical turning effect. Medicinally,
this is important for the treatment of inflammed tissues(Mota et al.,
1985). Several flavanoids and phenolic acids may present which exhibit
interesting antimicrobial properties. Numerous reports have been published
in the past three decades that focused on the antimicrobial properties
of herbs, species of their derivatives such as essential oils, extracts
and decoctions (Kivanc and Akgul, 1986). Aqueous extract of the different
concentration showed no inhibitory effects on the tested microorganisms
due to loss of some active compounds during extraction processes of the
sample. Despite many published reports dealing with treatment for neurological
disorders little was known about the antimicrobial activity of Bacopa
monnieri prior to our investigation. Further studies on the activity
directed fractionation for the isolation of respective pure compounds
result in interesting results.
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