Alfa-glucosidase inhibiting activity of Four GUATEMALAN PLANTS used in the treatment of type 2 diabetes.

Diabetes mellitus is defined as hyperglycemia 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 [1].

Among glucose-lowering medications, alfa glucosidase inhibitors (AGIs) delay the absorption of ingested carbohydrates, reducing the postprandial glucose and insulin peaks [2]. In nature two main kind of glucosidases exist: Type 1 are present in yeast and insects, they show higher activity toward heterogeneous substrates as sucrose and none or low toward homogeneous substrates as malto oligosaccharides, Type II are present in molds, plants and mammals, they hydrolyse the homogeneous substrates more rapidly [3]. In our field studies among the mayan cakchiqueles we detect the use of Croton guatemalensis Lotsy. (CG), Hamelia patens Jacq. (HP), Solanum americanum Mill. (SA), and Neurolaena lobata (L.) R. Br. (NL) to treat type 2 diabetes.

In previous studies, we demonstrated hypoglycemic activity in these plants. In the present work, we tested the alfa-glucosidase inhibitory activity of the plant extracts, in vivo by saccharose and maltose tolerance tests, and in vitro trough the inhibition of the enzymes isolated from Saccharomyces and from rat gut.

The tested plants did not reduce the hyperglycaemic peak under a maltose tolerance test, but AP, SA and NL did it under the saccharose test after 30 min. In vitro the extracts inhibit the glucosidase activity from Saccharomyces, but not that from rat gut (table 1). These results show that the plants can inhibit type 1 enzymes but not type 2.

[1] ADA AD. Classification and Diagnosis of Diabetes. Diabetes Care 2015; 38: S8-S16 Available from: http://care.diabetesjournals.org/cgi/doi/10.2337/dc15-S005

[2] Hanefeld M, Schaper F. In: Mogensen CE (ed.). Pharmacotherapy of Diabetes, New Developments. Springer, 2007: 143 – 152

[3] Kimura A et al. Carbohydr Res 2004; 339: 1035