Evaluation of the effect of Withania somnifera root extracts on cell cycle and angiogenesis

In the Indian System of Medicine, the medicinal plant, Withania somnifera Dunal (Solanaceae) finds application for numerous ailments including cancer. This study explores the mechanism(s) underlying this property. The hydroalcoholic extract of the roots (WS) was partitioned between chloroform (WS-chloroform) and water (WS-water). Further, WS-chloroform was fractionated (A1–A12) by reverse-phase column chromatography and their withanolide content was quantified by high-performance liquid chromatography (HPLC). Preliminarily, the anti-proliferative activity of all the extracts and fractions was screened against human laryngeal carcinoma (Hep2) cells by microculture tetrazolium assay (MTT). Two extracts (WS and WS-chloroform) and three fractions (A4, A5 and A6) negatively affected Hep2 viability at the concentration of 25 μg/ml and these were further investigated pharmacologically. Flow cytometry revealed cell cycle block and accumulation of hypoploid (sub G1) cells as the mode of anti-proliferative activity of all but A4. Their anti-angiogenic potential was investigated by a chickchorio-allantoic membrane (CAM) wherein a significant inhibition (p < 0.0001) of vascular endothelium growth factor (VEGF), induced neovascularization was recorded. The effect was confirmed in vivo by mouse sponge implantation method. These findings suggest that the roots of Withania somnifera possess cell cycle disruption and anti-angiogenic activity, which may be a critical mediator for its anti-cancer action.