Cytotoxic 20,24-epoxywithanolides from Physalis angulata.

A new withanolide, physangulide B (1), was isolated from calyxes of Physalis angulata. This compound was also present in the aerial parts along with the known physangulide (4), which was isolated as the acetonide 3, and 24,25-epoxywithanolide D (6). Structures of these compounds were determined by analysis of their spectroscopic data, which indicated the presence of a 20,24-epoxy group in both physangulides.