Withaferin A-related steroids from Withania aristata exhibit potent antiproliferative activity by inducing apoptosis in human tumor cells

► A series of new withanolides were isolated from Withania aristata. ► First examples of silyl ether-withaferin A derivatives. ► Five compounds of this series exhibited higher antiproliferative effects than withaferin A. ► Hoechst, Annexin V/PI and caspase-3 studies revealed that compounds induce apoptosis in HeLa cells. ► This study sheds more light on the potential of withanolides as anticancer agents.