CHARACTERIZATION OF ROOT EXTRACTS OF WITHANIA SOMNIFERA AND EFFECT OF ZINC SULPHATE AND SILVER NITRATE ON ANTIBACTERIAL ACTIVITY AGAINST CERTAIN HUMAN PATHOGENIC BACTERIA

Author(s): Dinesh Kumar, Archana Gajbhiye, Vipin Nagda and Asha Arora

Abstract: Objectives: There is a serious need for the expansion of new antibacterial agents from natural sources due to emergence of new infections and increase in bacterial drug resistance that have been developed over a period of time in bacteria. The present study was carried out to evaluate the effect of zinc sulphate solution on antibacterial activity of crude methanolic and aqueous extract of W. somnifera root and its phytochemical characterisation. Methods: Agar well diffusion assay, as well as micro broth dilution assays, were used for determination of antibacterial activity. The assay was performed in triplicate and tetracycline was used as the control. The methanolic and aqueous extracts of W. somnifera root was prepared by percolation method. Pathological isolates Escherichia coli, Staphylococcus aureus and Klebsiella pneumoniae were obtained from the Department of Microbiology, RNT Medical College & Hospital Udaipur (Raj.). Agar well diffusion method for antimicrobial susceptibility testing was performed. The antibacterial activities were assessed by the presence or absence of inhibition zones after incubating the plates at 37°C for 24 hours. Minimum inhibitory concentrations (MIC) for the selected pathogens were determined by broth micro dilution method. Results: Among aqueous and methanolic extracts, methanolic extract was found to possess a more potent inhibitory activity with a maximum zone of inhibition of S. aureus in antibacterial susceptibility test. MIC value of the extract for S. aureus was found to be 3.4 ±0.003 mg/ml. Among all the combinations, maximum antibacterial activity was found with methanolic extract in combination with of zinc sulphate producing a zone of inhibition of 19.00 +0.33 mm. The antibacterial effect was similar in all combinations of aqueous extract and metal salts. Conclusion: Both aqueous and methanolic root extracts of W. somnifera found to possess antibacterial activity against E. coli and S.aureus. The extracts were ineffective against K. pneumoniae. The metal salts such as zinc sulphate enhances the antimicrobial potential of the root extracts. The methanol extract of W. somnifera roots possess the ability to control pathogenic bacterial growth and may be further analysed for medicinal value in ethno medicine.

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