Further evaluation of antihyperglycaemic activity of Hunteria umbellata (K. Schum) Hallier f. seed extract in experimental diabetes

Ethnopharmacological relevance: In African traditional medicine, water decoction made from the dry seeds of Hunteria umbeltata (K. Schum) Hallier f. is highly valued in the management of diabetes mellitus. Aim: In the present study, the antihyperglycaemic activity of the seed aqueous extract of Hunteria umbellate (K. Schum) Hallier f. (HU) was investigated in alloxan-induced, high fructose- and dexamethasone-induced hyperglycaemic rats. Materials and methods: Alloxan-induced, dexamethasone-induced and high fructose-induced hyperglycaemic rats were treated with single, daily oral administration of 1 mg/kg of glibenclamide, 50 mg/kg, 100 mg/kg and 200 mg/kg of HU in Groups III, IV, V and VI, for 14 days, 21 days and 8 weeks, respectively. The effects of these drugs on FBG, free plasma insulin levels, HbA(1c), serum TG and TC, and insulin resistance indices were investigated. Results: Data generated in the current study showed that glibenclamide and graded oral doses of HU caused significant dose related (p < 0.05, <0.01 and <0.001) reductions in FBG when compared to the values obtained for the model control (Group II) rats. Similarly, daily oral administration of 66.7 g/kg fructose to rats for 8 weeks was associated with significant (p < 0.001) hyperglycaemia, elevations in plasma HbA(1c), free insulin, fasting insulin resistance indices, serum TG, and cholesterol. However, concomitant oral treatments with 1 mg/kg of glibenclamide, 50 mg/kg, 100 mg/kg, and 200 mg/kg of HU extract significantly and dose dependently (p < 0.05, <0.01 and <0.001) attenuated development of hyperglycaemia, decreased levels of plasma HbA(1c), free insulin, and serum triglyceride and cholesterol. in the Groups III, IV, V and VI rats. respectively, when compared to fructose-induced hyperglycaemic (Group II) rats. Similar effect was also recorded in the dexamethasone-induced hyperglycaemic rats. Conclusion: Results of this study suggest that the hypoglycaemic and antihyperlipidaemic effects of HU are mediated via enhanced peripheral glucose uptake and improvements in hyperinsulinaemia. (C) 2009 Elsevier Ireland Ltd. All rights reserved.