Fractionation and analysis of fluorescent products of lipid peroxidation

The fluorescence excitation spectrum of model conjugated Schiff base compounds that arise from the reaction of malonaldehyde with amino acids was shown to contain a maximum at 260-280 nm in addition to the previously observed maximum at 350-390 nm. Excitation at either maximum results in emission at a single maximum at 440-480 nm. The excitation and emission maxima of the model fluorescent compounds, together with the characteristic reductions in fluorescence intensity caused by alkaline pH or heavy metal coordination provide criteria with which to examine lipid peroxidation products for the presence of the conjugated Schiff base fluorophore. Silicic acid column chromatography and silica gel thin layer chromatography were employed to fractionate the fluorescent products of model lipid peroxidation systems and of rat testicular lipid soluble extracts. These products contained large families of compounds whose fluorescence characteristics were the same as those of the Schiff base fluorophores. The fractionation methods used enabled more thorough fluorescence characterization of many of the products of lipid peroxication, but the fluorescence criteria available do not provide definitive proof of structure.