Soybean insoluble Fiber-EGCG binary compounds: Enhanced stability and synergistic antioxidant activity

High-purity insoluble dietary fiber (HPSIDF) possesses distinct structural and functional characteristics. Epigallocatechin gallate (EGCG), a bioactive polyphenol with known anti-inflammatory properties, exhibits low bioavailability due to its susceptibility to degradation in the gastrointestinal tract. In this study, HPSIDF-EGCG binary complexes were fabricated through non-covalent interactions. Structural analyses confirmed that hydrogen bonding and hydrophobic interactions were the primary driving forces for complex formation. The HPSIDF-EGCG complexes significantly enhanced EGCG stability, with retention rates of 80.1 % in simulated gastric fluid and 86.6 % in intestinal fluid, effectively protecting EGCG from degradation. In addition, the complexes exhibited synergistically enhanced antioxidant activity, as indicated by a DPPH radical scavenging rate of 44.78 %, compared to only 4.91 % for HPSIDF alone. These findings support the use of HPSIDF as a functional carrier to improve EGCG bioactivity and suggest a sustainable approach to the high-value utilization of soybean processing by-products.