Synthesis of 7-hydroperoxycholesterol and its separation, identification, and quantification in cholesterol heated model systems.
7-Hydroperoxycholesterol is considered to be an intermediate compound of the cholesterol oxidation path as the first product formed when cholesterol is oxidized by triplet oxygen. However, there is a limitation on cholesterol mechanism studies because of the lack of 7-hydroperoxycholesterol analytical standard due to its low stability. To verify the formation of hydroperoxides in cholesterol model systems heated at 140, 180, and 220 °C, 7α-hydroperoxycholesterol was synthesized by cholesterol photooxidation followed by rearrangement at room temperature in chloroform. Its structure was confirmed on the basis of 13C NMR and mass spectra obtained by APCI-LC-MS. The synthesized compound was also used as standard for the quantification of 7-hydroperoxycholesterol as the sum of 7α- and 7β-hydroperoxycholesterol. The results demonstrated that 7-hydroperoxycholesterol is the first compound formed when the temperature is lower (140 °C). However, the concentration of the 7-hydroperoxycholesterol depends on the temperature and time of exposure: the higher the time, the higher the amount of 7-hydroperoxycholesterol at lower temperatures, and the lower the time, the lower the amount of 7-hydroperoxycholesterol at higher temperatures (180 and 220 °C). By the formation of 7-hydroperoxycholesterol, the known cholesterol oxidation mechanism in three phases (initiation, propagation, and termination) could be confirmed; once at lower temperatures, the stage of cholesterol oxidation is at initiation, at which hydroperoxide formation predominates.
Nogueira
Gislaine C
GC
Department of Food Science, Faculty of Food Engineering, University of Campinas, Campinas, SP, Brazil.
Costa
Bruna Z
BZ
Crotti
Antonio E M
AE
Bragagnolo
Neura
N
D002784:Cholesterol / Q000031:analogs & derivatives* / Q000032:analysis / Q000138:chemical synthesis / Q000737:chemistry / Q000302:isolation & purification; D006358:Hot Temperature; D007700:Kinetics; D008956:Models, Chemical; D055668:Photochemical Processes
C041011:cholesterol 7-hydroperoxide; D002784:Cholesterol