Three Megastigmane Glycosides from the Leaves ofPterospermum semisagittatum

Pterospermum semisagittatum leaves yielded three megastigmane glycosides (Z)-4-[3′-(β-D-glucopyranosyloxy) butylidene]-3,5,5-trimethyl-2-cyclohexen-1-one (1), (E)-4-[3′-(β-D-glucopyranosyloxy)butylidene]-3,5,5-trimethyl-2-cyclohexen-1-one (2) and (E)-4-hydroxy-4-[3′-(β-D-glucopyrano syloxy)butylidene]-3,5,5-trimethyl-2-cyclohexen-1-one (3). Their structures were established by detailed spectroscopic studies. Compound 3 showed a significant insulin releasing effect on rat pancreatic islets.