Photochemical degradation of cholesterol induced by anthraquinone

Abstract

Solar light irradiation of chloroform solutions or aqueous dispersions of cholesterol in the presence of anthraquinone (a powerful sensitizer of hydrogen-atom abstraction) yielded several photoproducts of which six compounds were identified using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) analyses. Non-acidic photoproducts (originating essentially from an initial hydrogen-atom abstraction at the carbon 7 position of the cholesterol molecule) included epimeric cholest-5-ene-3β,7-diols, 3β-hydroxy-cholest-5-en-7-one, cholesta-3,5-dien-7-one and2,3,3aα,6,7,7aα-hexahydro-7a-methyl-β-(1,5-dimethylhexyl)-indene. 2,6-Dimethylheptanoic acid, an interesting acidic cholesterol photoproduct derived from an attack of the carbon 17 position, was also detected. Different mechanisms were proposed to explain the formation of these compounds.