Remodeling the structure of soy protein fibrils to hydrogels for co-encapsulation of (−)-epigallocatechin gallate (EGCG) and curcumin: Role of EGCG

Curcumin (Cur) and (−)-Epigallocatechin gallate (EGCG) have synergistic bioactivity in several terms, but their polar differences and environmental sensitivity make co-utilization challenging. Soy protein fibrils (UF) have sparked broad attention as outstanding carriers for bioactive substances. In this study, EGCG was applied to remodel the structure of Cur-loaded UF complex (UFC) to form novel UF-based hydrogels co-encapsulated Cur and EGCG (UFCE). The fluorescence spectroscopy, ITC, and FTIR analysis demonstrated that EGCG absorbed and deposited on the surface of UFC through hydrophobic and electrostatic interactions. The binding of EGCG led to the formation of UFCE, which constructed a stable and uniform gel network during heat treatment. UFCE gels formed with varying EGCG/protein concentration ([E]/[F]) ratios showed different structural properties with different encapsulation effects. At 2.5% protein concentration, UFCE gels formed at [E]/[F] ratio of 0.08 (UFCE0.08) exhibited better gelling properties. The encapsulation efficiency of Cur and EGCG in UFCE0.08 gel was up to 97.71% and 91.02%, respectively. Moreover, UFCE0.08 gel exhibited significantly enhanced stability of Cur (95.27%) and EGCG (70.27%) than that of free Cur (53.13%) and free EGCG (13.32%) after thermal treatment at 85 °C for 120 min. UFCE0.08 gel was also effective in improving the UV light stability of Cur (88.70%) and EGCG (72.96%). Furthermore, the binding of EGCG had pronouncedly boosted the anticancer activity of Cur in the UFCE0.08 gel against Caco-2 cells. This study provides new perspectives into the fibril-polyphenol hydrogel systems for the co-encapsulation of EGCG and Cur, which has substantial potential for health-promoting applications.