Fluorescent products from reaction of peroxidizing polyunsaturated fatty acids with phosphatidyl ethanolamine and phenylalanine

Abstract

Fluorescent chromophores produced by reaction of peroxidizing arachidonic acid or methyl docosahexaenoate with synthetic dipalmityl phosphatidyl ethanolamine were lipid soluble, and those from reaction with phenylalanine were water soluble. In all reaction systems that contained polyunsaturated fatty acid and only one amine compound, the development of fluorescence was linearly related to oxygen absorption for 12–24 hr (p<0.001) and to the amount of thiobarbituric acid reacting materials until the rate of oxygen absorption decreased. The fluorochromes typically had maximum excitation at 360 nm and maximum emission at 430–440 nm, indicating that they were conjugated Schiff bases with the general structure R−N=C−C=C−N−R, where R represents the amino acid phenylalanine or the phospholipid phosphatidyl ethanolamine. The fluorochromes were similar to those extracted from isolated age pigments and tissues of animals that are aged, vitamin E-deficient, or stressed with highly unsaturated lipid diets.