Bioaccessibility and antioxidant capacity of epigallocatechin gallate interacting with mung bean protein: impact of protein structure†

The integration of plant proteins with bioactive compounds offers a promising strategy to enhance their environmental stability. This study investigated the complexation of mung bean protein (MBP) with epigallocatechin gallate (EGCG) and the impact of affinity differences resulting from structural variations of MBP on the performance of the resulting complexes. MBP fractions obtained via ammonium sulfate precipitation displayed distinct protein compositions, especially MBP-60%S, which was mainly 8S vicilin. MBPs and EGCG rely on hydrogen bonding and hydrophobic interactions for spontaneous self-assembly, with hydrogen bonding dominating in highly soluble MBP. EGCG binding induced structural changes in MBPs, including an increase in α-helix content and size, as well as a reduction in β-sheet content and solubility. Notably, MBP-60%S exhibited the strongest affinity for EGCG. These conformational shifts enhanced the thermal stability of EGCG, thereby mitigating the loss of antioxidant capacity due to its thermal degradation. Moreover, the bioaccessibility of EGCG was increased by 1.91–3.22-fold. However, MBP-60%SE showed resistance to gastric digestion, likely due to the altered protein structure and interaction strength. Overall, these findings provide valuable insights into the functionalization of plant proteins, offering a foundation for the development of high-quality functional foods and novel applications of mung bean protein.