In Vitro α-Amylase and α-Glucosidase Inhibitory Activities and Molecular Docking Analysis of Xylosma longifolia Clos. and Schima wallichii

Abstract

Background: Diabetes mellitus is a chronic metabolic disorder characterized by persistent hyperglycaemia. Inhibition of carbohydrate-hydrolysing enzymes, particularly α-amylase and α-glucosidase, represents an important approach for controlling postprandial blood glucose levels. Medicinal plants are promising sources of bioactive compounds with potential antidiabetic properties. The present study investigated the in-vitro α-amylase and α-glucosidase inhibitory activities of ethanolic leaf extracts of Xylosma longifolia Clos. (XLCLE) and Schima wallichii (SWLE), supported by molecular docking analysis. Methods: The α-amylase inhibitory activity was evaluated using a starch substrate and 3,5-dinitrosalicylic acid (DNS) reagent, with absorbance measured at 540 nm. α-Glucosidase inhibition was assessed using p-nitrophenyl-α-D-glucopyranoside (pNPG) as the substrate, with absorbance measured at 420 nm. Acarbose served as the reference inhibitor in both assays. Percentage inhibition and half-maximal inhibitory concentration (IC₅₀) values were used to evaluate the inhibitory potential of the extracts. Molecular docking was performed using the CDOCKER algorithm and the CHARMm force field to investigate ligand–protein interactions. Results: Both extracts exhibited concentration-dependent inhibition of α-amylase and α-glucosidase. As reported in the results narrative, XLCLE and SWLE exhibited α-amylase IC₅₀ values of 377.35 and 260.78 µg/mL, respectively, while their α-glucosidase IC₅₀ values were 171.63 and 150.29 µg/mL, respectively. SWLE demonstrated comparatively stronger inhibitory activity than XLCLE against both enzymes, although acarbose showed greater potency. Molecular docking identified fargesin as a promising ligand for α-amylase interaction, with a reported docking energy of −45.1745 kcal/mol and interactions involving key active-site residues, including Trp47, Leu139, Asp174, Lys177, His178, and Glu200. Conclusion: The findings indicate that the ethanolic leaf extracts of Xylosma longifolia and Schima wallichii possess in-vitro carbohydrate-hydrolysing enzyme inhibitory potential. The comparatively stronger activity of SWLE supports further investigation of its bioactive constituents. Molecular docking provides complementary evidence of potential ligand–enzyme interactions. Further phytochemical validation, mechanistic studies, and in-vivo investigations are required to establish their antidiabetic potential.