15-Hydroxylation of 5 beta-cholestan-3 alpha-ol and 24 alpha-ethyl-5 beta-cholestan-3 alpha-ol in rat liver supernatants (18,000 X g).

4-14C-labeled-5 beta-cholestan-3 alpha-ol and 24 alpha-ethyl-5 beta-cholestan-3 alpha-ol were incubated with rat liver 18,000 X g supernatant fractions fortified with NADPH. Among the metabolites formed were the 15 alpha- and 15 beta-hydroxy derivatives of the two substrates. The identification of these metabolites with liquid chromatography, thin layer chromatography, and gas-liquid chromatography-mass spectrometry is described. The formation of 15 beta-hydroxylated metabolites exceeded that of 15 alpha-hydroxylated ones. The total yields of 15-hydroxylated compounds formed was of the order 0.5-1.0%. The 15-hydroxylated metabolites could not be detected after incubations with rat liver mitochondria or a soluble liver fraction or after incubations of 5 beta-cholestan-3 alpha-ol with soybean lipoxygenase and linoleic acid.