COMPARATIVE ASSESSMENT OF THE INHIBITORY EFFECT OF SOME SELECTED PLANT EXTRACTS ON THE ACTIVITY OF ALPHA-GLUCOSIDASE ENZYME

Abstract

Diabetes mellitus remains a major global metabolic disorder characterized by chronic hyperglycemia resulting from impaired insulin secretion or action. One therapeutic strategy for reducing postprandial blood glucose involves inhibiting α-glucosidase, a key enzyme responsible for the terminal breakdown of dietary carbohydrates. This study comparatively evaluated the inhibitory potential of methanolic extracts from seven medicinal plants—Diospyros mespiliformis (Sample A), Stem bark (Sample B), Cassia nigricans (Sample C), Khaya senegalensis (Sample D), Ficus carica (Sample E), Bitter leaf (Vernonia amygdalina, Sample F), and Ficus sycomorus (Sample G)—against yeast α-glucosidase. Plant samples collected from the local forest at Usmanu Danfodiyo University were air-dried, pulverized, macerated in absolute methanol, and concentrated. Enzyme inhibition assays were performed using serial dilutions of each extract (100–3.125 mg/mL), with absorbance measured at 500 nm after a 5-minute incubation step. Data were analyzed using nonlinear regression to estimate IC₅₀ values. The nonlinear regression produced unstable IC₅₀ values for most extracts due to poor curve fitting and low inhibitory response, indicating weak or inconsistent inhibition across the tested concentration range. Extracts of Diospyros mespiliformis leaves, Khaya senegalensis, and Vernonia amygdalina displayed more consistent upper and lower plateaus, suggesting that they contained constituents capable of interacting with the enzyme. All the extracts exhibited minimal α-glucosidase inhibition at the studied concentrations.