OXIDATION OF CHOLESTEROL BY HEATING

Oxidation of pure cholesterol during heating in an air oven at high temperature was studied. Cholesterol was virtually stable during heating at 100-degrees-C for 24 h but was unstable at temperatures above 120-degrees-C. In the heated cholesterol preparations, a number of oxidized derivatives were detected by a combination of thin-layer chromatography and capillary gas chromatography-mass spectrometry. Major oxidized sterols were 7alpha-hydroxycholesterol, 7beta-hydroxycholesterol, 5alpha-epoxycholesterol, 5beta-epoxycholesterol, cholestanetriol, and 7-ketocholesterol. Various oxidized cholesterol derivatives were produced during heating above 120-degrees-C within a relatively short time (1 h). The composition of the oxidized products differed depending on temperature and time of heating. When cholesterol was heated at 150-degrees-C, the production of oxidized cholesterol was maximum, and 7-ketocholesterol was the most predominant oxidized product. Heating at 120-degrees-C also produced oxidized cholesterol to some extent, whereas only marginal amounts of oxidized cholesterols were produced at 100-degrees-C and at 200-degrees-C cholesterol was almost decomposed in a short time.