ABSTRACT
The geometric increase in the incidence of diabetes mellitus across the globe coupled with its long term complications and high cost of management have invigorated research on plants as alternative therapy in the management of diabetes mellitus. Vernonia amygdalina and Dacryodes edulis are well known for their therapeutic and medicinal values. In the present study, phytochemical screening, proximate and mineral analyses as well as the antioxidant and antidiabetic activities of the aqueous leaf extracts of these plants were determined.In vivo antidiabetic activities as well as other biochemical parameters were determined in six groups of alloxan-induced diabetic rats. Fasting blood glucose level was measured 72 hr after induction of diabetes with alloxan at a dose of 150 mg/kg and treatment commenced immediately. Diabetes mellitus was confirmed on the bases of fasting blood glucose above 250 mg/dL. The results of the preliminary phytochemical screening indicated the presence of phenolic compounds, flavonoids, tannins and saponins in the leaf extracts of V. amygdalina and D. edulis. HPLC analysis showed that luteolin, luteolin 7-0- beta glucoside, syringic acid, vanillic acid, piperic acid, 1,5-dicaffeoylquinic acid, 1,3,5- dicaffeoylquinic acid, chlorogenic acid, 4,5- dicarffeoylquinic acid, naringenin, gallic acid, caffeic acid and chlorogenic acid are present in the leaf extracts. Aqueous leaf extract of Vernonia amygdalina contained high concentrations of total phenol and total flavonoids (228.23 ± 39.53 and 120.00 ± 0.67 respectively) when compared to Dacryodes edulis (205 ± 28.27 and 80 ± 0.05 respectively) at p < 0.05 with correlated radical scavenging and α amylase inhibitory activity. In the experimental animals, both extracts significantly decreased blood glucose level (p < 0.05). There were also significant decreases in serum levels of TC, TAG and LDL-C and a significant increase in HDL-C (p < 0.05), when compared to diabetic control. Moreover, a significant increase in serum total protein and significant reductions in ALT, AST, ALP and total bilirubin (p < 0.05) were also seen, when compared to diabetic control (p < 0.05). In addition, there were significant decreases in serum urea and creatinine levels, while Na, Cl, HCO3 and K were increased significantly when compared to the diabetic group (p < 0.05). An improvement in tissue morphology of the β cells of the pancreas was recorded across the treatment groups.The results of the present study suggest that V. amygdalina and D. edulis and their infusions are efficacious in the management of diabetes mellitus.
