Bioactive saponins and glycosides. II. Senegae Radix. (2): Chemical structures, hypoglycemic activity, and ethanol absorption-inhibitory effect of E-senegasaponin c, Z-senegasaponin c, and Z-senegins II, III, and IV.

Following the characterization of E-senegasaponins a and b and Z-senegasaponins a and b, new bioactive saponins named E-senegasaponin c and Z-senegasaponin c were isolated from Senegae Radix, the root of Polygala senega L. var. latifolia TORREY et GRAY., together with Z-senegins II, III, and IV. The chemical structures of E and Z-senegasaponins c and Z-senegins II, III, and IV were elucidated on the basis of chemical and physicochemical evidence, and the geometrical isomeric structures of the 4"-methoxycinnamoyl and 3",4"-dimethoxycinnamoyl groups in these saponins were found to show tautomer-like behavior under irradiation with fluorescent lamps. E and Z-Senegasaponins c and E and Z-senegins II, III, and IV were found to exhibit hypoglycemic activity in the oral D-glucose tolerance test. (E) and (Z)-Senegins II also showed an inhibitory effect on alcohol absorption in rats.