Chain length-dependent antioxidant activity of phosphatidylcholine complexes of alkyl gallates in fish oil and emulsions: a reverse micelle interfacial mechanism

Non-monotonic chain length-dependent antioxidant activity of alkyl gallate-PC complexes in fish oil. • Short-chain complexes (C2) quench aqueous initiators at the hydrophilic interface. • Long-chain complexes (C12) intercept lipophilic radicals in the reverse micelle leaflet. • Excess PC micelles relocate long-chain complexes to the O/W interface for enhanced efficacy. In bulk oils, phosphatidylcholine (PC) and trace water form reverse-micelle interfaces that concentrate hydroperoxides and pro-oxidant metals, promoting oxidation. PC complexes of gallic acid and selected C1-C16 alkyl gallates were evaluated in fish oil and emulsions. Activity peaked at C2 (ethyl gallate-PC, EG-PC) and C12 (dodecyl gallate-PC, DG-PC) rather than changing progressively with chain length. After accelerated oxidation, EG-PC and DG-PC showed the lowest peroxide values (25.27 and 24.53 mmol/kg oil) and TBARS values (7.00 and 6.89 mg MDA/kg oil), while preserving polyunsaturated fatty acids and suppressing aldehyde formation. Spectroscopy supported complexation, whereas cryo-TEM, CLSM, and SAXS supported reverse-micelle formation. We propose that PC anchors gallates at this interface, the short-chain EG-PC localizes near the hydrophilic region to quench aqueous-phase initiators, whereas the long-chain DG-PC partitions into the lipophilic region to intercept chain-propagating radicals. In emulsions, excess PC micelles further relocate DG-PC to the interface, enhancing its efficacy. Download: Download high-res image (263KB) Download: Download full-size image