Palbinone, a Novel Terpenoid from Paeonia albiflora; Potent Inhibitory Activity on 3.ALPHA.-Hydroxysteroid Dehydrogenase.

Palbinone, a novel terpenoid isolated from the roots of Paeonia albiflora, showed a strong inhibitory activity on the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH)-linked 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) of rat liver cytosol. The structures of palbinone and a known compound, paeonilactone-B isolated from the active fraction of this plant were determined by the use of 2D NMR techniques (1H-1H COSY, 1H-13C COSY, 1H-13C long-range COSY, and HMBC).