Effect of Natural Products on Some Glycosidases and Their Expected Hypoglycemic Potential

Aims: It is to screen many natural product extracts for their in vitro and in vivo effects on the activities of hepatic α-amylase and α-glucosidase to validate their biological importance.

Study Design: Different groups of non-diabetic and diabetic rats were treated by different plants for the in vivo study of glycosidases. In vitro effect of the plants on the tested enzymes was studied in presence and absence of their aqueous extract.

Place and Duration of Study: Department of Biological & Environmental Sciences, Faculty of Science, Beirut Arab University, Beirut, Lebanon, between March 2013 and February 2014.

Methodology: Enzymes were extracted from the livers of normal rats, also the natural products extracts were prepared for the in vitro studies. α-Amylase and α-glucosidase assays were done in the presence and absence of each plant extract. For the in vivo studies, normal non-diabetic rats were divided into groups, whereas the first group is a control that includes rats fed on normal food diet. The other groups include rats fed on normal food diet mixed with the tested plant leaves (20 mg/g body weight/day) Diabetes was induced in diabetic rats by single intraperitonial injection of streptozotocin. Diabetic rats were divided into groups and treated like the non-diabetic rats.

Results: Only Thymus vulgaris and Origanum vulgare extracts showed a significant in vitro dose-dependent inhibition on α-amylase with IC50 values of 0.2±0.01 and 0.37±0.03mg/ml, respectively. However, the in vivo effect was not detected for four weeks treatment for the two enzymes. The in vitro treatment of α-amylase by Thymus vulgaris and Origanum vulgare extracts exhibited a mixed-type inhibition. Moreover, the in vivo inhibition of both extracts on the tested hepatic enzymes was not detected in streptozotocin-induced diabetic rats fed on Thymus vulgaris and Origanum vulgare for four weeks. Blood sugar level was non-significantly decreased with respect to that of non-treated rats.

Conclusion: some non anti-diabetic plant extracts possess an in vitro inhibition of glycosidases.