Effects of triterpenoids from Pueraria lobata on immunohemolysis: beta-D-glucuronic acid plays an active role in anticomplementary activity in vitro

The anticomplementary properties of kaikasaponin III (4) and soyasaponin I (8) from Pueraria lobata and their hydrolytic analogs were investigated in vitro. Diglycosidic saponins [kaikasaponin I (3), soyasaponin III (7)] show ed most potent anticomplementary activities, followed by monoglycosidic sap onins [soyasapogenol B monoglucuronide (6), sophoradiol monoglucuronide (2) ] and triglycosidic saponins [soyasaponin I (8), kaikasaponin III (4)], whe reas sophoradiol (1) and soyasapogenol B (5) showed enhancement of hemolysi s under the presence of serum on the classical pathway of complement system . But all of them showed very weak or no anticomplementary activities on th e alternative pathway of complement system. The anticomplementary activity of the saponins was influenced by the nature of glucuronic acid, where the free acid forms (-COOH) showed much more potent activity than the sodium sa lt forms (-COO-Na+) or methyl ester forms (-COOCH3), and the reduced forms (-CH2OH) decreased the activity significantly.