ABSTRACT
The geometric increase in the incidence of diabetes mellitus across the globe couple with its long term complications and high cost of management has invigorated research into 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 leaves extracts of these plants were determined.The aqueous leaves extracts of V. amygdalina and D. edulis were subjected to preliminary phytochemical analysis via qualitative chemical tests and HPLC was used to identify the polyphenols present in the plants extracts. Alpha amylase inhibitory activity, total phenol and flavonoid contents, DPPH (1,1-diphenyl-2-picrylhydrazyl), total reducing power, ferric reducing power as well as total antioxidant capacity were conducted to assess the antidiabetic and antioxidant capacity of the leaves extracts respectively. In vivo antidiabetic activities as well as other biochemical parameters were determined in alloxan induced diabetic rats.36 adult male Wistar rats were used for the study. The rats were randomly divided into six groups of six animals in each group. Animals in group 1 were not induced (normal control), while group 2 (Untreated diabetes) animals were induced (via intraperitoneal injection of 150mg/kg of alloxan). Animals in groups 3, 4, 5, 6 were induced and treated with 70mg/kg of metformin, 300mg/kg of Dacryodes edulis, 200mg/kg of Vernonia amygdalina and 500mg/kg of combined Vernonia amygdalina and Dacryodes edulis respectively for two weeks. Fasting blood glucose level was measured 72 hours after induction of diabetes with 150mg/kg of alloxan and treatment commenced immediately. Fasting blood glucose above 250mg/dL confirmed diabetes mellitus. The results of the preliminary phytochemical screening indicated the presence of phenolic compounds, flavonoids, tannins and saponins in the leaves 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 leaves 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) compared to Dacryodes edulis (205 ± 28.27 and 80 ± 0.05) (p < 0.05) with correlated radical scavenging and α amylase inhibitory activity. Both plants showed DPPH IC50 values of 5.77 ± 0.002 (V. amygdalina) and 16.02 ± 0.001(D. edulis) as well as α amylase IC50 values of 16.46 ± 0.04 (V. amygdalina) and 18.12 ± 0.03 (D. edulis) respectively. In experimental animals, both extract decreased significantly the blood glucose level (P < 0.05). There was also a significant decrease in serum level of TC, TAG, LDL-C and a significant increase in HDL-C (P < 0.05) when compared to diabetic control. A significant increase in serum total protein and significant reduction in ALT, AST, ALP and total bilirubin (P < 0.05) was also recorded when compared to diabetic control (p < 0.05). There was also a significant decrease in serum Urea and creatinine, while Na, Cl, HCO3 and K 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 result of the present study suggests that V. amygdalina and D. edulis as well as their infusion are efficacious in the management of diabetes mellitus.
Keywords: Vernonia amygdalina, Dacryodes edulis, diabetes mellitus, metformin, alpha amylase, antioxidants, oxidative stress, polyphenols.
