Formation of the 5,6-epoxy derivatives of 7-hydroxy-cholesteryl-3β-acetates during peroxidation of cholesteryl acetate

The thermal peroxidation of cholesteryl acetate (CA) generates many compounds, most of which have been identified in previous studies. The trimethylsilyl (TMS) derivatives of the thermodegradation products of the single hydroperoxides of CA (7 alpha- and 7 beta-) gave GC-MS spectra that were almost identical to those of the thermal peroxidation of CA, except for four compounds that were only detected as TMS derivatives. These substances were identified by comparing their mass spectra and their GC retention time against those of the four synthesized isomers of the epoxy-hydroxy derivatives of CA. The presence of a considerable amount of epoxy-hydroxy derivates of CA, especially at low-temperature degradations, provides an explanation for the formation of other substances that have been previously identified.