| Abstract
| - The reaction of 4-hydroxy-2-nonenal, an oxidative stress product, with phenylalanine in acetonitrile−water (2:1, 1:1, and 1:2) at 37, 60, and 80 °C was investigated to determine whether 4-hydroxy-2-alkenals degrade amino acids, analogously to 4,5-epoxy-2-alkenals, and to compare the reactivitiesof both hydroxyalkenals and epoxyalkenals for production of Strecker aldehydes. In addition to theformation of N-substituted 2-pentylpyrrole and 2-pentylfuran, the studied hydroxyalkenal also degradedphenylalanine to phenylacetaldehyde with a reaction yield of 17%. The reaction mechanism issuggested to be produced through the corresponding imine, which is then decarboxylated andhydrolyzed. This reaction also produced a conjugated amine, which both may be one of the originsof the produced 2-pentyl-1H-pyrrole and may contribute to the development of browning in thesereactions. 4-Hydroxy-2-nonenal and 4,5-epoxy-2-decenal degraded phenylalanine in an analogousextent, which is likely a consequence of the similarity of the degradation mechanisms involved. Theseresults suggest that different lipid oxidation products are able to degrade amino acids; therefore, theStrecker type degradation of amino acids produced by oxidized lipids may be quantitatively significantin foods. Keywords: Carbonyl−amine reactions; epoxyalkenals; flavor production; hydroxyalkenals; lipidoxidation; Maillard reaction; nonenzymatic browning; phenylacetaldehyde; pyrroles; Strecker aldehydes
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