H₂O₂-induced green synthesis of EGCG-flavonoid carrier-free nanoparticles:The role of hydroxyl group number governing formation and function.

This study developed a green, carrier-free EGCG-flavonoid nanoparticle assembly strategy driven by H₂O₂. This approach overcomes the drawbacks of traditional formaldehyde-induced methods, including solvent toxicity and poor biocompatibility. It further investigated how the number of flavonoid hydroxyl groups regulates the assembly process and properties of EGCG-flavonoid nanoparticles. The formation involves H₂O₂-mediated oxidation of EGCG hydroxyl groups to generate aldehyde and carboxyl groups, which then undergo covalent bonding with the amino group of glycine. Flavonoids are embedded into the EGCG-glycine network through noncovalent interactions, resulting in spherical nanoparticles (200-260 nm, PDI ≈ 0.3). Increasing hydroxyl groups on flavonoids enhanced their loading capacity and interaction with EGCG. Nanoparticles with polyhydroxylated flavonoids exhibited strong antioxidant activity (>85% DPPH•/ABTS•+ scavenging), high storage stability (>70% retention after 60 days), and improved thermal stability. This work provides a theoretical foundation for green synthesis of polyphenol-flavonoid nanosystems in functional foods and targeted delivery.