Neighboring amide participation in the Fenton oxidation of a sulfide to sulfoxide, vinyl sulfide and ketone relevant to oxidation of methionine thioether side chains in peptides

Methionine thioether reduces the content of 4-hydroxy-2-nonenal in high-temperature soybean oil by preventing the radical chain reaction

This study investigated how methionine (Met) reduced 4-hydroxy-2-nonenal (4-HNE) generation during the heating of soybean oil. The results showed that Met at 5 mM, 10 mM, 15 mM, 20 mM and 30 mM reduced the 4-HNE content by 0.67 %, 58.86 %, 66.35 %, 86.62 % and 82.39 %, respectively, as detected by liquid chromatography coupled to tandem mass spectrometry. Additionally, a decrease in the content of alkyl radicals, alkyl peroxyl radicals and alkoxyl radicals with increasing Met concentration was detected by electron spin resonance. Combined with the subsequent identification of the adducts of Met with the three radicals, it could be shown that Met reduces the 4-HNE content by preventing the free radical chain reaction. Finally, the kinetics simulations of the reaction between 4-HNE and Met indicated that adducts formed by the two cannot be stabilized in high-temperature systems. This study offers insights into safe oil processing and the antioxidant mechanisms of Met thioether.