Studies on peroxidized lipids. VI. Fluorescent products derived from the reaction of primary amines, malonaldehyde and monofunctional aldehydes

Abstract

Abstract Monofunctional aldehydes such as acetaldehyde, n ‐propylaldehyde, n ‐butylaldehyde, n ‐hexylaldehyde, n ‐heptylaldehyde and benzaldehyde affected the reaction between primary amines and malonaldehyde. While the reaction of primary amines and malonaldehyde at pH 7 produced fluorescent 4‐methyl‐1,4‐dihydropyridine‐3,5‐dicarbaldehydes Ia‐f , the reaction of the primary amines, malonaldehyde and the aldehydes listed above gave fluorescent 4‐substituted 1,4‐dihydropyridine‐3,5‐dicarbaldehydes IIa‐j . The primary amines used for this reaction included alkylamines, amino acids and alkanolamines. The optimal ratio of the amine, malonaldehyde and the aldehyde was 1:2:1–2, at which compounds II were produced quantitatively. Peroxidized lipids which may contain malonaldehyde and other aldehydes could react with the primary amines to produce highly fluorescent II . Fluorescence spectra of II showed excitation maxima at 386–403 nm and emission maxima at 444–465 nm in phosphate similar to those of I . The spectra of these 1,4‐dihydropyridines I and II were roughly similar to those of lipofuscin pigment, but they exhibited different characteristics in acid and alkaline media from those of lipofuscin pigment. Compounds II may be useful as model compounds to elucidate the chemical structure of lipofuscin pigment.