Transesterification of cholesteryl esters

The transesterification of cholesteryl stearate, oleate, linoleate, linolenate and arachidonate to the fatty acid methyl ester and free cholesterol under mild conditions is described. In adaptation of a published procedure the transesterification was carried out for two hr at room temperature in 1N NaOH in methanol:benzene (60:40, v/v). After addition of saturated sodium chloride solution the reaction mixture was extracted with ethyl acetate. The product mixture was checked for cholesterol oxides by HPLC fractionation followed by measurement of the oxides by direct on‐column capillary GC. Although transesterification of cholesteryl stearate and oleate was complete (>99%) in 30 min, a uniform reaction period of two hr, required by the polyunsaturated esters, was used for all cholesteryl esters. 7‐Ketocholesterol, a principal oxidation product, was unaffected by the reaction conditions.