The sensitized photooxidn. of cholesterol (I) was carried out in several solvents and gave cholest-6-en-3b,5a-diol, cholest-5-en-3b,7a-diol and -3b,7b-diol and cholest-5-en-3b-ol-7-one (II). The product distribution depends on sensitizer and solvent used. In particular, a new product II is formed in the lumiflavin (LF)-sensitized photooxidn. of I. The rates of the photooxidns. in polar solvents are considerably faster than that in nonpolar solvents which are favorable to the formation of IV. Based on the results, it is proposed that the photooxidn. proceeds mainly via a singlet oxygen (1O2) pathway.

Key words: OXIDATION, PHOTOOXIDATION, CHOLESTEROL, STEROL, SENSITIZATION, STERONE, SINGLET OXYGEN, FLAVOPROTEIN, LUMIFLAVIN