Characterization of side-chain oxidation products of sitosterol and campesterol by chromatographic and spectroscopic methods

Based on the cholesterol-lowering effects of phytosterols, known since the 1950s, extra phytosterol amounts have been added to certain food products for almost 10 yr. Literature reports on oxidation of phytosterols in general are limited, and data on side-chain oxidation of these compounds are scarce. The aim of this study was to investigate and characterize autoxidation products from a mixture of the two phytosterols sitosterol and campesterol. A commercial mixture of the two sterols was oxidized for 72 h at 120degreesC in an air-ventilated oven. The oxidation products were separated by preparative TLC and identified and characterized with GC-MS. The following oxidation products were identified from the two phytosterols: 24-methylcholest-5-en-3beta,24-diol, 24-methylcholest-5-en-3beta,25-diol, 24-methylcholest-4-en-6alpha-ol-3-one, 4-methylcholest-4-en-6beta-ol-3-one, 24-ethylcholest-5-en-3beta ,24-diol,24-ethylcholest-5-en-3beta, 25-diol, 24-ethylcholest-4-en-6alpha-ol-3-one, 24-ethylcholest-4-en-6beta-ol-3-one. Full-scan mass spectra of these compounds are reported for the first time as their trimethylsilyl-ether derivatives.