Abstract
Unsaturated fatty acids such as linoleic, linolenic and arachidonic acids produced a complex mixture of fluorescent substances with an excitation maximum at 355-370nm and an emission maximum at 420-440nm by reaction with methylamine at pH 7.5 and 37°C. The excitation and emission maxima of the products shifted to higher wavelength with increasing unsaturation of the fatty acid, and were similar to those of lipofuscin pigments. The fluorescence characteristics of the products indicated that they were different in structure or composition with different fatty acids, and the major fluorescent products were neither 1-substituted-4-methyl-1, 4-dihydropyridine-3, 5-dicarbaldehydes [Kikugawa et al., Chem. Pharm. Bull., 29, 1423 (1981)] nor the conjugated Schiff bases [Chio and Tappel, Biochemistry, 8, 2821 (1969)] which were produced by reaction of malonaldehyde (MDA) with primary amines. Both thin-layer and high performance liquid chromatographies suggested that thiobarbituric acid-reactive substances other than MDA contributed to the formation of the fluorescent substances.
