Evaluation of in vitro Hypoglycemic Activity and Mechanism of Action of Olax scandens Roxb. Stem Bark Extracts

Background: Olax scandens Roxb. (Olacaceae) is a scandent thorny shrub used by many ethnic tribes of Asia to cure stomach ache, diarrhoea, fever, cough, mouth ulcers, anaemia, filaria, joint pains, intestinal and liver diseases and diabetes. Objectives: The present study was undertaken to investigate the in vitro hypoglycemic activity and mechanism of action of O. scandens stem bark extracts in five different in vitro models at different glucose concentrations. Materials and Methods: Various extracts of O. scandens stem bark was studied for their effect on glucose adsorption, glucose diffusion, glucose uptake by yeast cells, alpha glucosidase and alpha amylase inhibition at different glucose concentrations. Results: In the glucose adsorption method, the butanolic extract showed statistically significant increase in glucose bound concentration of 7.35 mM/L at 100 mM glucose concentration used. All extracts showed a significant retardation in glucose diffusion across a dialysis membrane into the external medium, at different time intervals. GDRI of ethyl acetate extract was 84.471 at 30 min whereas the butanolic extract and aqueous ethanolic extract showed highest GDRI of 80.267 and 70.386 at 120 min respectively. In the method of glucose uptake by yeast cells, aqueous ethanolic and butanolic extracts both showed significantly higher uptake of glucose of 65% at 5 mg/mL concentration. The ethyl acetate extract and standard acarbose showed 26.25% and 35% inhibition of alpha glucosidase respectively at 100 μg/mL concentration. Whereas at the same concentration, ethyl acetate extract and acarbose showed 48.922% and 63.093% inhibition of alpha amylase. Conclusion: Significant in vitro hypoglycemic activity was seen in glucose diffusion method suggesting a possible role of fibre which may retard glucose release across the dialysis membrane. This mechanism can be correlated with retardation in the transport of glucose across the intestinal lumen thus causing a reduction in post prandial hyperglycemia.