Hypoglycemic and hypolipidemic effects of tectorigenin and kaikasaponin III in the streptozotocin-induced diabetic rat and their antioxidant activityin vitro

Tectorigenin and kaikasaponin III from the flowers of Pueraria thunbergiana showed potent hypoglycemic and hypolipidemic effects in the streptozotocin -induced diabetic rats. Intraperitoneal administration of these two compoun ds with 5 and 10 mg/kg, respectively, for seven days to streptozotocin-indu ced rats significantly reduced the blood glucose, total cholesterol, LDL- a nd VLDL-cholesterol and triglyceride levels when compared with those of con trol group. Glycitein in which 5-OH is unlinked and tectoridin (7-O-glycosi de of tectorigenin) isolated from the flowers of Fl thunbergiana did not im prove hyperglycemia and hyperlipidemia. In addition, tectorigenin showed in vitro antioxidant effects on 1,1-diphenyl-2-pirylhydrazyl (DPPH) radical, xanthine-xanthine oxidase superoxide anion radical, and lipid peroxidation in rat microsomes induced by enzymatic and non-enzymatic methods. We furthe r found that tectorigenin and kaikasaponin III protected the Vero cell line (normal monkey kidney) from injury by hydrogen peroxide. From these findin gs, it seems likely that the antioxidant action of tectorigenin and kaikasa ponin III may alleviate the streptozotocin-induced toxicity and contribute to hypoglycemic and hypolipidemic effects.