A NOVEL FLUORESCENT MALONDIALDEHYDE-LYSINE ADDUCT

We report a novel type of fluorescent product derived from the reactio n of the lysine residue with malondialdehyde (MDA). When the lysine-co ntaining peptide (N-acetyl-glycyl-L-lysine methyl ester) was treated w ith MDA prepared by the acid hydrolysis of 1,1,3,3-tetramethoxypropane , the main fluorescent product, which corresponded neither to the 1-am ino-3-iminopropene derivative (2) nor to the 4-methyl-1,4-dihydro-3,5- dicarbaldehyde derivative (3), was detected by reverse-phase HPLC. By analysis of its UV, NMR, and high-resolution FAB mass spectra, it was confirmed to be l)-3,5-diformyl-1,4-dihydropyridin-4-yl]pyridinium (1) . This finding may provide a new clue to the formation mechanisms of f luorescent lipofuscin-like pigment.