Alfa-glucosidase inhibiting activity of five Mexican plants used in the treatment of type 2 diabetes

Diabetes mellitus is defined as hyperglycemia that is associated with inadequate insulin secretion, either in the presence or absence of impaired insulin action. Type 2 diabetes is characterized by tissue insulin resistance combined with a relative deficiency in insulin secretion. An individual may present primarily with either insulin resistance or beta cell deficiencies, and these abnormalities can range from mild to severe. Among glucose-lowering medications, α-glucosidase inhibitors delay the absorption of ingested carbohydrates, reducing the postprandial glucose and insulin peaks.

The root of Smilax moranensis M. Martens y Galeotti, Smilacaceae (SM), the stem of Tournefortia hirsutissima L., Boraginaceae (TH), the cortex of Rhizophora mangle L., Rhizophoraceae (RM), the cortex of Cecropia obtusifolia Bertol, Urticaceae (CO), and the leaves of Bromelia plumieri (E. Morren.) L.B. Sm., Bromeliaceae (BP), are used in Mexican traditional medicine to treat type 2 diabetes; our work group proved the hypoglycemic effect of these plants.

In the present study, we tested the extracts with respect to their α-glucosidase inhibitory activity, without excluding other possible mechanisms of action.

Our results in nicotinamide-STZ diabetic rats loaded with maltose showed that all the plants extracts decreased plasma glucose significantly from 30 min compared with the diabetic control group. In vitro assays of rat intestinal α-glucosidase showed that CO decreased activity by 45% at 1000 µg/ml and BP by 30% at 2000 µg/ml, while SM, TH and RM showed less than 20% inhibition at 1000 µg/ml.

These results suggest that inhibition of glucose absorption is not the main mechanism through which these plants reduce plasma glucose and contribute to understanding the mechanism of action of these plants on glucose metabolism