This study was conducted to determine the use of medicinal plants as an antibacterial agent and its potential to as an alternative medicine against bacterial infections. For this purpose Sequential extracts (i.e. Hexane, Chloroform, Ethanol and Aqueous) of Gymnema sylvestre R.Br. were tested against S. aureus, E. coli, S. enterica, C. perfringens type-A, H. paragallinarum. Of each bacterium 3 isolates were tested by using well diffusion method. The results were obtained by determining the ZOI by well diffusion method and MIC by using 96 well ELISA plate.
The mean ZOI and mean MIC values of G. sylvestre leaves extracts showed that chloroform and ethanolic extracts have more antibacterial activity against all five microorganisms. Only chloroform and ethanolic extracts showed antibacterial activity against all 5 microorganisms while hexane extract showed antibacterial activity against S. enterica, S. aureus, H. paragallinarum, C. perfringens type- A but no activity was observed against E. coli. On the other hand aqueous extract have showed antibacterial activity only against C. perfringens type-A but no antibacterial activity against remaining four bacteria under study. While analyzing results based upon MIC, the chloroform extract has more antibacterial effect when compared with hexane. Hexane extract was more potent than aqueous extract whereas ethanolic extract was the least potent.
When overall antibacterial effect of all the extracts was evaluated against all bacterial strains, it was observed that C. perfringens type-A was the bacterium most vulnerable to antibacterial activity of sequential extracts of dried leaves of G. sylvestre as it responded
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to all four sequential extracts and gave maximum zone of inhibition (10-22mm range) while no other bacteria showed such bigger zone of inhibition.
On the basis of MIC, it can be assumed that chloroform extracts have more antibacterial components as compared to hexane extract. Hexane extracts have more antibacterial components as compared to ethanolic extracts. The activity of aqueous extracts is negligible as it showed response against only one bacterium.
MTT assay was performed on supersaturated solutions of sequential extracts of dried leaves of G. sylvestre. Results revealed that small concentrations of these extracts are not toxic. Cell survival percentage (CSP) values below 50% were given at concentrations of 5800μg/ml (38.76%), 7225μg/ml (43.71%), 8150μg/ml (44.90%) and 3125μg/ml (41.84%) by hexane, chloroform, ethanolic and aqueous extracts respectively. Finally, on the basis of MIC and CSP for all of four sequential extracts, it is concluded that chloroformic extract is the most active and safe extract against all of 5 experimental bacteria, while hexane extract is safe against only C. perfringens type-A and ethanolic and aqueous extracts are cytotoxic on their MIC values for all the experimental bacteria. Statistical analysis showed that ZOI and MIC values were significantly different between the groups while within the same group they were non-significant.
Finally it can be concluded that the leaves of plant Gymnema sylvestre R.Br. cultivated in Pakistan has considerable antibacterial activity and considerable safety profile so it must be further studied, characterized, purified and chemically isolated so that may be converted to proper dosage form and this miracle plant may be used therapeutically to cure various ailments including bacterial infections especially poultry infections.