Preparation of autoxidized cholesterol mixtures from [4-14C] cholesterol and cholesteryl fatty acid esters

Autoxidation of non-esterified cholesterol, in the solid state, at 100 degrees C, is known to be a relatively slow reaction. The presence of carefully chosen cholesteryl esters considerably increases the ratio of autoxidation. Using this method, mixtures of autoxidized free cholesterol (oxycholesterol) labelled on carbon 4 can be obtained almost quantitatively, in the presence of benzoyl peroxide. The ratio of [4-14C] ester produced by transesterification at the end of the reaction is about 10%.