New isoflavones and pterocarpane with hepatoprotective activity from the stems of Erycibe expansa

The methanolic extract from the stems of Erycibe expansa was found to show a hepatoprotective effect on D-galactosamine-induced cytotoxicity in primary cultured mouse hepatocytes. By bioassay-guided separation, two new prenylisoflavones and a pterocarpane, erycibenins A (1), B (2), and C (3), were isolated from the active fraction (the EtOAc-soluble fraction) together with ten Isoflavones (4-13) and seven pterocarpanes (14-20). The stereostructures of the new compounds were determined on the basis of chemical and physicochemical evidence including modified Mosher's method. In addition, the isolated constituents, erycibenin A (1, IC50 = 79 microM), genistein (6, 29 microM), orobol (7, 36 microM), and 5,7,4'-trihydroxy-3'-methoxyisoflavone (8, 55 microM) exhibited inhibitory activity on D-galactosamine-induced cytotoxicity in primary cultured mouse hepatocytes.