Phytochemical Investigation and Antimicrobial Activity of Root Extracts of Withania Somnifera (L.) Dunal. against Drug-Resistant Bacterial Pathogens

With the emergence of multidrug resistance among clinical bacterial pathogens there is a growing need for the development of herbal alternatives for the effective therapeutic management of bacterial infections. Plants and plants products have long been used in traditional folk medicine worldwide. Hence this study was designed to test the antimicrobial efficacy of Withania somnifera L. Dunal. (root) against drug resistant bacterial pathogens. Extracts of W. somnifera (L.) Dunal (root) was prepared by cold percolation method. Antimicrobial activity of different solvent extracts of W. somnifera (L.) Dunal. (root) was studied against drug-resistant clinical isolates of Gram-positive cocci (vancomycin resistant Enterococcus faecalis and Methicillin resistant Staphylococcus aureus) and Gram-negative bacilli (ESBL Escherichia coli and Pseudomonas aeruginosa). The standard strains of ATCC 25922 E. coli, ATCC 25923 S. aureus, ATCC 27853 P. aeruginosa, and ATCC 29212 E. faecalis were used as controls. Antibacterial activities of extracts were evaluated using agar well diffusion method. Minimum inhibitory concentration was determined by microbroth dilution method. All the extracts (methanol, ethanol, acetone and chloroform) were inhibitory to gram positive bacteria tested. Nevertheless, inhibitory effect waspronounced in the methanol and ethanol extract, against gram negative bacteria (Both ATCC and clinical strains).Further based on the phytochemical and GC-MS analysis, it could be speculated that the antibacterial activity exhibited by the methanol extract of W. somnifera root could be attributed to the presence of phenolic compounds, flavonoids, steroids and terpenes.