Inhibition of α-amylase and α-glucosidase enzymes by extracts of plants of the genus Zanthoxylum

Diabetes mellitus type 2 represents 90% of all cases of diabetes, being characterized by a series of metabolic dysfunctions, including hyperglycemia. The literature points to ɑ-amylase and ɑ--glucosidase as potential therapeutic targets for the development of medicines to treat postprandial hyperglycemia. Among the plants of the semiarid region of Bahia, species of the genus Zanthoxylum have phytochemicals with pharmacological potential not yet explored. Therefore, the present work aims to evaluate the in vitro effect of crude extracts of some plants of the genus Zanthoxylum on the enzymes α-amylase and α-glucosidase. A total of eleven stem, stem bark and leaf extracts of Z. monogynum and Z. rhoifolium were obtained by cold maceration in the hexane, ethyl acetate, ethanol and methanol solvents. The extracts were incubated with ɑ-amylase or α-glucosidase, and residual enzyme activities were determined. Phenolics were quantified by the Folin-Ciocalteau method. All extracts reduced enzyme activity, especially the methanolic leaf extract of Z. monogynum reduced ɑ-amylase activity (53.5%) and the stem bark extract of Z. rhoifolium of ɑ-glucosidase (99.2%). In any experiment the inhibitory effect correlated with the concentration of phenolic compounds (p > 0.05). The half maximal inhibitory concentration (IC50) values of the extracts in the case of ɑ-amylase was 25.9 and 61.5 µg/mL, while in α-glucosidase IC50 values were between 21.6 and 26.5 µg/mL. The results indicate that the extracts are potentially useful for the treatment of diabetes. Further phytochemical studies directed to the isolation of bioactive molecules and characterization of the mechanism are needed.