ABSTRACT

Diabetes mellitus is a chronic metabolic disorder which alters several cellular, tissue, organ and system functions, often leading to death. This research, however, was designed to determine the effects of the methanol and aqueous extracts of V. doniana leaves on diabetes mellitus. The antioxidant parameters, membrane stabilisation, Na+/K+-ATPase activity, glycated haemoglobin and electrolytes concentrations were measured using spectrophotometric methods. Other parameters such as the fasting blood glucose concentration, body weights and histopathology of the pancreas were also determined. Thirty-five albino male rats of 4-7 weeks old, weighing 70-140 g were used for this study. The rats were housed in steel cages and acclimatised for one week prior to the experiment. The rats were induced with diabetes using streptozotocin at 65 mg/kg body weight (bwt). The rats were grouped into seven. Group 1 was the normal control, given animal feed and distilled water; group 2, the drug control, received 5 mg/kgbwt of glibenclamide. Group 3 was the negative control, diabetic but not treated. Groups 4 and 5 were given 400 and 800 mg/kgbwt of the aqueous extract respectively whereas groups 6 and 7 received 400 and 800 mg/kgbwt of the methanol extract respectively. The administration lasted for 28 days. Phytochemical analysis of the methanol extract of the leaves indicated the presence of flavonoids, alkaloids, tannins, glycosides, phenols, reducing sugars, steroids, saponins, soluble sugars, terpenoids and hydrogen cyanide. Acute toxicity study showed the relative safety of the extracts at 5000 mg/kgbwt. Generally, there were significant (p<0.05) increases in the fasting blood glucose concentrations of all diabetic rats compared to that of the rats in the normal control. However, prior to sacrifice, all the treated rats showed normal concentrations of fasting blood glucose. There was no significant (p>0.05) difference in body weights of rats across all groups. There was no significant (p>0.05) difference in the glycated haemoglobin concentration of rats across all groups compared to that of the rats in the normal control. Also, there was a significant (p<0.05) increase in the activity of Na⁺/K⁺-ATPase of rats in group 6 while rats in  group 3 recorded a significant (p<0.05) low activity. The activities of SOD and CAT showed a significant (p<0.05) increase in rats of all treated groups while there was no significant (p>0.05) difference in GP_X activities of rats in all treated groups compared to that of the rats in the normal control. Rats in group 6 showed a significant (p<0.05) reduction in MDA concentration. The methanol extract showed a higher membrane stabilising potential than the drug glibenclamide at 5 mg/kgbwt. Concerning electrolytes, there was generally a significant (p<0.05) reduction of Cl^- in rats across all treated groups. A significant (p<0.05) reduction in HCO₃^- was recorded in group 7. Rats in groups 2 and 7 also showed significant (p<0.05) reductions in Na⁺ and Ca²⁺ across all treated groups compared to that of the normal control. Histopathology results revealed considerable regeneration of the pancreatic beta cells of the rats in groups treated with the methanol and aqueous extracts of V. doniana leaves. The results obtained from this research clearly indicate the effectiveness of the methanol and aqueous extracts of V. doniana leaves as antidiabetics.