Hypoglycemic and antioxidant effects of Rheum franzenbachii extract in streptozotocin-induced diabetic rats.

The hypoglycemic and antioxidant effects of ethanol extract from the roots and rhizomes of Rheum franzenbachii Münt. (Polygonaceae) were evaluated in streptozotocin-induced diabetic rats. Effects of repeated oral administration of ethanol extract (125, 250, and 500 mg/kg body weight) on the plasma glucose level (PGL), oral glucose tolerance test (OGTT), malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) in diabetic rats were examined. It was found that administration of ethanol extract (125, 250, and 500 mg/kg) produced a significant fall in PGL, AUC, and MDA, while elevating the GSH levels and SOD and CAT activities in diabetic rats. The dose of 500 mg/kg was identified as the most effective dose, with a decrease of 65.8 and 44.0% in PGL and MDA, and elevation of 72.6, 75.0, and 51.5% in GSH level and SOD and CAT activities, respectively, after 14 days of ERF administration in diabetic rats. Moreover, the OGTT studies showed a maximum reduction in PGL and AUC. From the active extract of Rheum franzenbachii, two stilbenes, desoxyrhapontigenin (1) and desoxyrhaponticin (2), were isolated as major constituents. The present study concludes that the ethanol extract of roots and rhizomes from Rheum franzenbachii had significant hypoglycemic and antioxidant effects.