Abstract
Polyunsaturated fatty acids esterified to phospholipids, triglycerides and cholesterol esters are important targets for lipid peroxidation, and this leads to production of their peroxides in biological tissues. All linoleic acid hydroperoxides esterified to their backbones yielded fluorescent substances through reaction with 1-aminopentane as a model amino compound in the presence of heme. These fluorescent substances were eluted as major fluorescence peaks (FS-IIIp, FS-IIIt and FS-IIIc) at different retention times on high-performance liquid chromatography. Each FS-III was hydrolyzed with the respective hydrolytic enzymes, phospholipase A2, lipase and cholesterol esterase, and was converted to the same fluorescent substance (FS-II) as that formed from methyl linoleate hydroperoxide. The fluorescent substances obtained showed the same fluorescence spectra with excitation and emission maxima at around 350 and 420 nm, respectively. These results indicate that esterified peroxides in phospholipids, triglycerides and cholesterol esters produce esterified fluorescent substances through reaction with amino compounds, resulting in the accumulation of fluorescent substances with age in biological tissues. Moreover, the actions of phospholipase A2, lipase and cholesterol esterase may lead to elimination of these fluorescent substances from the biological tissues.
