Hydrogen Peroxide-Mediated Degradation of Polygalacturonic Acid Produces Oligogalacturonides with Antioxidant and α-Glucosidase Inhibitory Activities: A Structural and Molecular Simulation Study

Pectin-derived polygalacturonic acid exhibits valuable bioactivities yet suffers from poor solubility that limits its application in the food and pharmaceutical industries; the controllable preparation of uniform oligogalacturonides (OGAs) remains a key technical bottleneck. This work aimed to establish an eco-friendly depolymerization route for polygalacturonic acid and clarify the structural features and combined hypoglycemic-antioxidant bioactivities of the resulting OGAs. Hydrogen peroxide was used as a green degradation reagent to break polygalacturonic acid chains, and target OGAs were recovered via ethanol precipitation. Multiple characterization techniques including FT-IR, NMR, HPAEC and UPLC-MS/MS were adopted to analyze the chemical structures of OGAs, while in vitro radical scavenging and α-glucosidase inhibition assays combined with molecular simulation were conducted to assess biofunctions and binding mechanisms. Structural identification confirmed that OGAs contained esterified and non-esterified galacturonic acid backbones with minor neutral sugar branches, with degrees of polymerization distributed from 3 to 11. OGAs exerted obvious concentration-dependent antioxidant capacity, achieving 78.68% DPPH and 73.98% ABTS radical clearance at 18 mg/mL, and reached 57.14% α-glucosidase inhibition at 1.5 mg/mL. Molecular simulation proved that longer OGAs form stronger hydrogen bond interactions with enzyme active pockets, with binding energy decreasing from -9.8 kcal/mol (GalA₃) to -16.0 kcal/mol (GalA₈). This green H₂O₂ degradation method enables efficient preparation of structurally defined OGAs, and the dual antioxidant and hypoglycemic properties of OGAs support their promising potential for exploitation in functional foods and antidiabetic agents.