Objective: The present study was aimed to investigate the possible mechanism of action of the active sub fraction of C. rutidosperma. This was done by in vivo and in vitro method.Methods: Aqueous extract of C. rutidosperma was sequentially fractionated and re-fractionated to yield the active sub fraction (based on in vivo evaluation). In the in vivo study, the active sub fraction was administered to streptozotocin-induced diabetic mice at graded doses in different prandial states; while for the in vitro method, assessment of the possible effects of the active sub fraction of the plant on glucose absorption by excised ileum as well as its effect on α-glucosidase, α-amylase and glucose 6 phosphatase activities was evaluated.Results: There was significant reduction of blood glucose level by the active sub fraction at different prandial states. The active sub fraction produced comparable hypoglycemic effects as glibenclamide. Likewise, at the doses of 125 and 62.5 mg/kg b. w., it significantly (p<0.05) reduced postprandial hyperglycemia after administration. Glucose tolerance was significantly (p<0.05) improved in the presence of the active sub fraction to varying degrees. The active sub fraction of C. rutidosperma did not demonstrate inhibitory effects on glucose movement into external solution across the rats excised ileum except at 50g/L and 25g/L where a significant (p<0.05) inhibition of glucose movement was observed. Alpha-amylase inhibitory activity of the active sub fraction was found to be 22. 24% at the lowest concentration of 2.50 mg/ml while the highest concentration of 20.00 mg/ml gave 46.66% inhibition. On the other hand, acarbose (standard) showed inhibition of 16.00 % and 34.43% for its lowest and highest concentrations for α-amylase respectively. Similarly, the α-glucosidase inhibitory activity results were: 16.42% and 44.56% for C. rutidosperma and acarbose respectively for the lowest concentration of 2.50 mg/ml, while the highest concentration of 20mg/ml had 64.22% and 87.09% for C. rutidosperma and acarbose respectively. Also, the active sub fraction of the plant showed significant inhibitory activity against glucose 6-phosphatase in a dose dependent fashion.Conclusions: The results revealed that the possible antihyperglycemic mechanism of action of the plant may be by reduction of postprandial hyperglycemia and improvement of glucose tolerance activity by stimulation of insulin secretion from pancreatic cell and inhibition of carbohydrate hydrolysing enzymes. Consequently, C. rutidosperma may be used as a dietary adjunct to counter hyperglycemia and it has the potential to be developed as new oral antidiabetic agent for the treatment of diabetes mellitus.Â
