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A new red coloration induced by the reaction of oxidized lipids with amino acids

Nakamura, T., Hama, Y., Tanaka, R., Taira, K., Hatate, H.
Journal of agricultural and food chemistry 1998 v.46 no.4 pp. 1316-1320
pigmentation, lipids, amino acids, oxidation, stereoisomers, pigments
The characteristics of the red coloring reaction of oxidized lipids were studied using a stereoisomer (R1) of 3-(2-ethyl-5-hydroxy-3-oxocyclopentyl)-2-propenal and amino acids. Maximum color formation was observed at neutral pH and with a higher concentration of amino acid. This red coloration was observed with almost all alpha-amino acids tested, beta-Ala and peptides of Gly but not with amides, amines, ammonia, cytosine, and the methyl ester of Gly. Each amino acid yielded its own red pigments: the red pigments were eluted at distinct positions with reversed-phase HPLC and showed slightly different absorption maxima (510-524 nm). Fluorescence on the red pigments was nil. The skeletons of 14C- and 3H-labeled amino acids were incorporated into the red pigments, and both carbonyl groups (IR v 1740, 1690 cm-1) of R1 were responsible for formation of the red pigments. These reaction characteristics were different from those of reducing sugars, ascorbic acid, and related substances.