Binding mechanisms of quinone-modified EGCG (QEGCG) with plant proteins: Enhanced foaming-emulsifying properties and improved hypoglycemic activity

Plant protein has attracted wide attention due to its sustainability, but its poor foaming and emulsifying properties limit its application. EGCG can cross-link proteins to improve functional properties, but it is easily oxidized to quinone form (QEGCG), which may have different protein interaction mechanisms from natural EGCG. This study investigated the interaction mechanism between QEGCG and plant proteins. Multi-spectral and molecular docking showed that QEGCG formed a more broken and porous stable complex through covalent/non-covalent interactions, with a stronger binding. These structural changes resulted in significantly enhanced foaming and emulsifying properties (pea protein 2.84 × and chickpea protein 3.2 ×) compared to EGCG. The QEGCG-conjugate had stronger inhibition on α-amylase (70.02%) and α-glucosidase (77.27%). Quinoa protein could delay the intestinal release of QEGCG by 33.39% in simulated digestion, achieving synergistic functional complementation. These findings provide strategies for broadening the application of QEGCG, improving the function of plant proteins, and developing hypoglycemic foods.