The antidiabetic activity of aqueous, ethanolic and hexanic extracts of Bauhinia forficata was investigated in a model of alloxan-induced diabetes in rats. The biochemical parameters studied were: plasma glucose, serum triglycerides, cholesterol, high density lipoprotein (HDL), and low density lipoprotein (LDL). Extracts were administered daily for 7 d at doses of 200 and 400 mg/kg, p.o., 48 h after alloxan injection (60 mg/kg, i.v.). The alloxan-diabetic rats showed significant reductions in plasma glucose, triglycerides, total cholesterol and HDL-cholesterol after treatment with the extracts and glibenclamide (used as standard) as compared to the diabetic controls. Levels of LDL were not altered. In conclusion, our results showed that the plant extracts when administered by gavage may reduce glucose, triglycerides, total cholesterol and HDL-cholesterol levels. These results suggest the validity of the clinical use of B. forficata in the treatment of diabetes mellitus type II.

Abstract:Cissus verticillata (syn. C. sycioides, fam. Vitaceae) is a medicinal plant popularly used in Brazil, for the treatment of diabetes mellitus. The anti-diabetic activity of a fraction from leaves of Cissus verticilllata (MSF, methanol soluble fraction), as well as that of tyramine (TYR) were investigated, in the model of alloxan-induced diabetes, in male Wistar rats. The biochemical parameters studied were: serum glucose, triglycerides (TG), total cholesterol (TC) and very low density lipoprotein (VLDL), urea, creatinine, AST and ALT levels. Besides, glycated hemoglobin and liver glycogen concentrations were also determined. The MSF (50 and 100 mg kg , i.v.). Drugs were administered alone or associated. Alloxan-diabetic rats showed significant reductions in plasma glucose, triglycerides and total cholesterol, after the treatment with the MSF, tyramine and glibenclamide, as compared to diabetic controls. The MSF and TYR effects were not potentiated by their association with GLI. Besides, MSF or TYR did not reverse DZ-induced hyperglycemia. However, MSF and TYR effects were significantly potentiated by MET, suggesting that these drugs act by a mechanism similar to that of MET. The other biochemical parameters were unaltered. The treatment of diabetic animals with the MSF increased the number of pancreatic beta cells. TYR also decreased the concentration of glycated Hb. While a 61% decrease in glycogen concentration was observed in diabetic controls, a total and partial recoveries of alloxan effects were seen after treatment of diabetic animals with the MSF (100 mg kg −1 , p.o.) and measurements carried out 2 and 24 h after amyloglicosidase addition, respectively. In conclusion, our results showed that the MSF and TYR, when administered by gavage for 5 days, may reduce glucose, TG and TC levels by a mechanism at least in part similar to that of MET. These results point to the insulin-like effects of C. verticillata, probably due to the presence of tyramine in the plant.

In the present study, the antioxidant activity of a methanol soluble fraction (MSF) from Cissus verticillata, used in Brazil and elsewhere as a hypoglycemic and antidiabetic medicinal plant, and tyramine (TYR), one of its main bioactive constituents, was assessed. For this, male Wistar rats were submitted to alloxan injection (40 mg/kg, i.v.) in order to induce a diabetic state and, 48 h later, glycemia was determined. Animals were distributed into groups: normal controls (NC); diabetic controls (DC); DC plus MSF; and DC plus TYR. Another group was treated with glibenclamide (GLI), used as a positive control. After 5-day treatments, animals were sacrificed for liver dissection, and determination of antioxidant markers such as thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), catalase and nitrite concentrations. The antioxidant effect was also evaluated on the pentobarbital-induced sleeping time, before and after CCl4 treatment. Under our experimental conditions, diabetic rats did not present any alteration in liver lipid peroxidation, before (DC) or after treatments with the MSF; TYR or GLI, as compared to normal controls (NC). Levels of GSH were significantly increased in 79% in DC, as related to NC, and the effects were partially reversed in diabetic rats, after MSF treatments at the higher dose. However, while similar effects were observed after TYR and GLI, both drugs brought values of GSH to normality. The DC group had increased liver catalase activity, as compared to NC, and these effects were partially reversed by MSF and almost completely by TYR and GLI. Significant increases were also detected in nitrite concentrations in livers of DC, as an index of free radical formation, and a large reduction was observed after MSF, TYR and GLI treatments of diabetic rats, as compared to NC. MSF and TYR also prevented prolongation of the pentobarbitalinduced sleeping time by CCl4, suggesting hepatoprotective and anti-oxidative effects. In conclusion, we showed that the antioxidant activity probably plays an important role in the antidiabetic effect of C. verticillata, and TYR is at least in part responsible for this property.