Plant alpha-amylase inhibitors: steady kinetic study, Bidens odorata aqueous infusion toxicity and stability in digestive tract simulation

α-Amylase inhibitors are considered an important therapeutic target to control type 2 diabetes mellitus, reducing postprandial hyperglycemia. Medicinal plants are an important source with inhibitory activities of this enzyme, but little studied. The present study explored the α-amylase inhibition with extracts of 11 medicinal plants available in Saltillo, Mexico; the kinetic mechanism of inhibition of selected extracts and their phytochemical screening; evaluation of the toxicity of Bidens odorata extract in Artemia salina model, as well as estimation of its inhibitory effect under in vitro digestive tract conditions. The inhibitory assays were carried out spectrophotometrically with aqueous suspensions of the extracts obtained after evaporation of solvent from aqueous and ethanolic infusions. Eleven plants showed an inhibitory effect of α-amylase above 10% of the initial activity at 666.7 ppm. Four plants were selected for kinetic assay due to inhibitory effect near or higher than 20 %. The IC50 for the aqueous suspension of the ethanolic extract of Bidens odorata was 851 ppm similar to that detected with the drug acarbose. The inhibition mechanism for Bidens odorata, Cinchona succirub, and Opuntia ficus-indicata was competitive, and for Cnidoscolus chayamansa it was uncompetitive. All selected extracts presented flavonoids, the majority contained terpenoids, 3 contained tannins and phenols. The aqueous infusion of Bidens odorata - model of a functional drink, showed no toxicity and was characterized by resistance for 60 min to simulated stomach and intestinal conditions in vitro. The findings of this study revealed the species of medicinal plants, which were not previously considered as sources of α-amylase inhibitors, and their kinetic mechanisms of inhibition, which can be used for functional hypoglycemic food preparation.