Withanolide derivatives from Physalis angulata var. villosa and their cytotoxic activities

A comprehensive phytochemical investigation of the leaves and twigs of Physalis angulata. var. villosa resulted in the isolation of 23 withanolide derivatives, including one novel 13,20-γ-lactone withanolide derivative (1) and three new withanolide derivatives (2-4). Architecturally, physalinin A (1) represents the first identified type B withanolide featuring a 13,20-γ-lactone moiety. The molecular structures of all isolates were elucidated using an integrated approach combining nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), infrared (IR) spectroscopy, and quantum chemical calculations to confirm structural assignments. The antiproliferative activities of all isolated withanolides were evaluated against four human cancer cell lines (HEL, HCT-116, Colo320DM, and MDA-MB-231). Among them, eight derivatives (2, 5-8, 14, 15, and 23) exhibited significant inhibitory effects, with half-maximal inhibitory concentration (IC₅₀) values of 0.18 ± 0.03 to 17.02 ± 0.21 μmol·L^-1. Structure-activity relationship (SAR) analysis suggested that the presence of an epoxide ring enhances anticancer activity, potentially through increased reactivity or specific interactions with molecular targets involved in cancer progression. These findings underscore the pharmacological potential of withanolides as promising lead compounds for the development of novel anticancer therapeutics.