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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.