Unraveling the Antioxidant Potential of Tectochrysin: A Quantum Chemical Approach to Radical Scavenging Mechanisms

In this study, we conducted a comprehensive quantum chemical investigation to elucidate the antioxidant mechanisms of tectochrysin via hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) pathways. All calculations were performed at the BMK/6-311+G(d,p) level in both gas and aqueous phases, complemented by intrinsic reaction coordinate (IRC) and transition state analyses. The HAT mechanism with hydroxyl radicals was determined to be both thermodynamically ΔG = –18.13 kcal/mol and kinetically ΔG# = 14.93 kcal/mol favorable, with a reaction rate nearing diffusion control k = 6.17 × 10¹² dm³/mol·s. SPLET became dominant in polar media, supported by a significantly stabilized anionic form. Conversely, SET-PT and NO-radical pathways were found to be mechanistically irrelevant. Molecular docking simulations revealed a favorable binding affinity of tectochrysin to oxidative stress-related proteins, mediated by hydrogen bonding and hydrophobic interactions. This integrated study provides valuable mechanistic insights into tectochrysin's antioxidant potential and highlights its pharmacological promise as a multi-pathway ROS scavenger.