Determination of regioisomeric hydroperoxides of fatty acid cholesterol esters produced by photosensitized peroxidation using HPLC

In order to examine the process of the lipid oxidation, the regioisomers of hydroperoxides produced by the photosensitized peroxidation of cholesteryl oleate, cholesteryl linoleate and cholesteryl Linolenate by photosensitize d peroxidation and the separation of each isomer by HPLC were investigated. The olefinic parts in fatty acid chains of the above cholesteryl esters re ceived hydroperoxidation predominantly by photosensitized oxidation. Choles teryl oleate was subjected to hydroperoxidation at the 9 and 10 position of the oleic acid chain. Cholesteryl linoleate and cholesteryl linolenate wer e also subjected to hydroperoxidation at the 9, 10, 12 and 13 positions of the linoleic acid chain and at the 9, 10, 12, 13, 15 and 16 positions of th e linolenic acid chain, respectively. Hydroperoxidation on the cholesteryl ring was also observed, however, their formation was negligibly small compa red with hydroperoxidation of the fatty acid chain. The elution order of is omeric peroxides in HPLC was determined using a normal-phase column (Mighty sil 60) eluted with hexane/2-propanol by the detected wavelength at 210 and 233 nm.