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.

RESULTS

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 studied.

Table 1:	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 concentration

DISCUSSION

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.