Radiation-induced reactions of cholesterol in an aqueous medium

60Co γ-ray radiolysis of cholesterol (3β-hydroxy-5-cholestene) (I) in the two-phase system (water-ethyl acetate) and in the presence of air was studied using thin-layer chromatography and gas chromatography methods. The following products were observed in the irradiated mixture: 3β,7β-dihydroxy-5-cholestene (II), G 0.36, 3β-hydroxy-7-keto-5-cholestene (III), G 1.48, 3β-hydroxy-7-keto-5α-cholestane (IV), G 0.22, 3β,5,6β-trihydroxy-5α-cholestane (V), G 0.83, 5,6α-epoxy-3β-hydroxy-5α-cholestane (VIa), G 0.26, 5,6β-epoxy-3β-hydroxy-5β-cholestane (VIb), G 0.24, and 2α,3β-dihydroxy-5-cholestene (VII) G 0.22. The dose dependence of the formation of these products shows that the cholesterol derivatives substituted in the position 7 (II-IV) are formed from a common precursor - the radical Ia. On the other hand, the products of the 5-C=C double bond reactions (V and VI) and also the product VII are formed independently. A reaction scheme agreeing with these results is proposed. (author)