Natural α-amylase inhibitors may be beneficial in reducing the release of oligosaccharides from starch and
thereby delaying glucose absorption. This research aimed to evaluate the inhibitory effect against α-amylase and
the inhibition mode of hydroethanolic extracts from seven plants traditionally used in the treatment of type II
diabetes. In this study, phenolic compounds were quantified, and the antioxidant activities of the extracts were
determined in terms of their free radical scavenging capacity and iron-reducing power. Their ability to inhibit
porcine pancreatic α-amylase in vitro was tested, and the inhibition modes were determined from the Lineweaver-
Burk plot. Results showed that all studied plants exerted inhibition against α-amylase. The lowest median
inhibitory concentrations (IC50 values) were obtained with C. occidentalis (0.031 μg/mL) and S. bicolor (0.036
μg/mL), showing that they are the most effective. C. sinensis showed the greatest flavonoid content (13.89 μg/100
mg). Enzyme kinetics showed an uncompetitive and non-competitive type of inhibition. Principal component
analysis revealed chemical proximity between Sorghum bicolor and Cassia occidentalis. Both extracts were
positively associated with high phenolic content and low IC₅₀ values. Therefore, S. bicolor stems and C.
occidentalis leaves, used separately, could contribute to the reduction of postprandial blood glucose by inhibiting
α-amylase activity.

α-amylase inhibition; antioxidant activities; medicinal plant; inhibition type; postprandial hyperglycemia.