Bioactive constituents from Chinese natural medicines.: XXIII.: Absolute structures of new megastigmane glycosides, sedumosides A4, A5, A6, H, and I, and hepatoprotective megastigmanes from Sedum sarmentosum

The methanol-eluted fraction of the hot water extract from the whole plant of Sedum sarmentosum (Crassulaceae) was found to show hepatoprotective effect on D-galactosamine-induced cytotoxicity in primary cultured mouse hepatocytes. From the active fraction, five new megastigmane glycosides, sedumosides A(4), A(5), A(6) H, and I, were isolated together with 22 megastigmane constituents. Their absolute stereostructures were elucidated on the basis of chemical and physicochemical evidence. Among them, sedumoside F-1 (IC50,,=47 mu M), (3S,5R,6S,9R)megastigmane-3,9-diol (61 mu M), and myrsinionosides A (52 mu M) and D (62 mu M) were found to show the strong hepatoprotective activity.