Isolation, characterization and evaluation of antimicrobial activity of Withanolide-A of Withania somnifera

Abstract

The increasing prevalence of multidrug resistant strains of bacteria and the recent appearance of strains with reduced susceptibility to antibiotics raises the specter of untreatable bacterial infections and adds urgency to the search for new infection-fighting strategies. The WHO estimated that approximately 80% of world population relies mainly on traditional medicines, mostly plant drugs in their health care. About 30% of the currently used therapeutics is of natural origin. Withania somnifera Dunal is widely used in Ayurvedic medicine, the traditional medical system of India. The alkaloid (Withanolide A) was obtained from 50% ethanol extract of Withania somnifera stem, subjected to column chromatography on silica gel eluted with a stepwise gradient of increasing order (Ethyl acetate: hexane). White crystals in ethyl acetate were obtained from ethyl acetate: hexane fraction. The aim of the present study was to investigate the in vitro antibacterial activity of the alkaloid, was screened against pathogenic bacteria of clinical origin including two species, Pseudomonas and Staphylococcus aureus . The growth inhibition was observed in four of the five tested pathogens at three different of Withanolide-A concentrations (100, 500, and 1000 ppm).The result indicates that the WithanolideA exhibited significant antibacterial activity against the Pseudomonas and Staphylococcus aureus .