Scientific Evidence for Anticancer Effects of Withania somnifera and Its Primary Bioactive Component Withaferin A

Abstract

Withania somnifera (WS) plant has been used for centuries to cure or treat various disorders in the Ayurvedic medicine. Research over the years has indicated that withanolides are the primary bioactive constituents in WS. Scientific evidence for anticancer effects of WS root extract (WRE) is quite strong, and is derived from both in vitro cellular experiments and in vivo studies in rodent models of cancer. This article reviews scientific evidence supporting anticancer effects of WRE and its primary withanolide (withaferin A). The primary focus of the present article is on: (a) phytochemistry of WS, (b) withanolide biosynthesis, (c) pharmacokinetics, (d) in vivo evidence for anticancer activity of WRE and its primary bioactive component withaferin A (WA), and (e) effect of WA and WRE on cancer stem cell population and/or epithelial-mesenchymal transition. Unpublished results from our own laboratory are presented to demonstrate that WA is the most likely primary anticancer agent in WRE standardized for WA content (sWRE). The mechanisms underlying anticancer effects of WRE and WA have been reviewed extensively by us and others, and therefore are not elaborated in this article.