COMPARATIVE EVALUATION OF THE IN VITRO α-GLUCOSIDASE INHIBITORY ACTIVITY OF GRAPE, FIG, AND BLUEBERRY EXTRACTS

Abstract

Diabetes mellitus is a chronic metabolic disorder characterized by persistent hyperglycemia, and inhibition of α-glucosidase is considered an effective approach for reducing postprandial blood glucose levels. The present study aimed to comparatively evaluate the in vitro α-glucosidase inhibitory activity of grape (Vitis vinifera), fig (Ficus carica), and blueberry (Vaccinium caesariense) extracts and to investigate their potential as natural antidiabetic agents. Fruit extracts were prepared by homogenization, centrifugation, filtration, pasteurization, and dilution. The inhibitory activity was determined spectrophotometrically using p-nitrophenyl-α-D-glucopyranoside (pNPG) as the substrate, while acarbose served as the positive control. Among the tested samples, grape extract exhibited the highest inhibitory activity (43.31 ± 1.97%), followed by fig (29.47 ± 1.97%) and blueberry (15.96 ± 3.95%). The IC₅₀ value of acarbose was estimated to be approximately 0.53 mg/mL. Enzyme kinetic analysis based on the Lineweaver–Burk plot indicated that grape extract inhibited α-glucosidase predominantly through a competitive inhibition mechanism. These findings demonstrate that the tested fruit extracts contain bioactive compounds capable of inhibiting α-glucosidase activity, with grape extract showing the greatest inhibitory potential. Therefore, these fruits may serve as promising natural sources of bioactive compounds for the development of functional foods and complementary strategies for the management of postprandial hyperglycemia.