Biochemical Characterization of the Antioxidant and α-Amylase Inhibitory Activities of Mucuna pruriens Leaf Extract: Insights from Enzyme Kinetic Analysis

Abstract

The increasing prevalence of type 2 diabetes mellitus has intensified the search for plant-derived therapeutics capable of simultaneously attenuating oxidative stress and regulating carbohydrate metabolism. Although Mucuna pruriens is recognized for its medicinal properties, the antioxidant potential and enzyme inhibitory mechanism of its leaf extract remain poorly understood. This study investigated the in vitro antioxidant activity, α-amylase inhibitory potential, and inhibition kinetics of ethanolic leaf extract of M. pruriens. Antioxidant capacity was evaluated using hydroxyl radical, lipid peroxidation, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays with butylated hydroxyanisole (BHA) as the reference antioxidant. α-Amylase inhibitory activity was determined across different extract concentrations, while Lineweaver–Burk kinetic analysis was employed to elucidate the mode of enzyme inhibition. The extract exhibited appreciable antioxidant activity in all assay models, demonstrating hydroxyl radical, lipid peroxidation, and DPPH scavenging activities of 55.77 ± 1.66%, 47.00 ± 1.40%, and 45.34 ± 3.72%, respectively, although significantly lower than BHA (P < 0.05). The extract inhibited α-amylase in a concentration-dependent manner, increasing from 45.83 ± 1.55% at 1.10 mg/mL to 59.24 ± 1.11% at 2.30 mg/mL, surpassing acarbose (56.24 ± 0.82%) at the highest concentration tested, with an IC₅₀ of 1.40 mg/mL. Kinetic analysis revealed a reduction in apparent Vmax (0.27 mM min⁻¹) accompanied by an altered Km (0.39%), indicating a mixed mode of α-amylase inhibition. These findings demonstrate that M. pruriens leaf extract possesses dual antioxidant and antihyperglycaemic activities through free radical scavenging and modulation of α-amylase activity, highlighting its potential for future antidiabetic drug development.