Antioxidant mechanism of indole-Maillard reaction products in hot-pressed flaxseed oil: a combined experimental and theoretical approach

Flaxseed oil’s high polyunsaturated fatty acid (PUFA) content renders it susceptible to oxidation, a process that compromises its quality and shelf life. This study investigated the antioxidant mechanisms of indole-Maillard reaction products (IMRPs) generated during the hot-pressing of flaxseed using integrated experimental and computational approaches. Among the identified IMRPs, N-acetyl-5-hydroxytryptamine (NA-5-HT) exhibited the strongest radical scavenging capacity, attributable to the low bond dissociation energy (BDE) of its phenolic hydroxyl group. Mechanistic analysis revealed that IMRPs effectively inhibit the initiation phase of oxidation by scavenging alkyl radicals (R·) with low activation barriers, thus reducing primary oxidation. However, their capacity to scavenge alkylperoxyl radicals (ROO·) during the propagation phase was limited by higher energy barriers, which accounts for their minimal impact on secondary oxidation. These findings elucidate the stage-selective antioxidant behavior of IMRPs, and provide a theoretical basis for optimizing processing to enhance oil stability.