RESUMO
Superoxide radical anion (O-2) failed to react with cholesterol under a variety of conditions. In some instances products indicative of free radical oxidation by molecular oxygen (O2) were found, but no products of electronically excited (singlet) molecular oxygen (1O2) attack on cholesterol were detected. These results do not support a direct role of O-2 in lipid peroxidation of cholesterol-rich membranes or of the formation of 1O2 from O-2 dismutation.
Assuntos
Colesterol/metabolismo , Oxigênio/metabolismo , Superóxidos/metabolismo , Animais , Fenômenos Químicos , Química , Grupo dos Citocromos c/metabolismo , Eletroquímica , Hidrólise , Técnicas In Vitro , NADPH-Ferri-Hemoproteína Redutase/metabolismo , Oxirredução , Fotoquímica , RatosRESUMO
The facile acid-catalyzed conversion of cholest-5-ene-3 beta, 7 alpha-diol (but not of cholest-5-ene-3 beta, 7 beta-diol) in methanol or ethanol solution to the corresponding 7 alpha-methyl or 7 alpha-ethyl ethers and epimerization of the 7 alpha-alkyl ethers to the corresponding 7 beta-alkyl ethers were established. The epimeric cholest-5-ene-3 beta, 7-diols, their 7-methyl ethers, and their 7-ethyl ethers are readily interconverted in acidified solvents, the quasiequatorial 7 beta-epimer predominating in each case. Both 7 alpha- and 7 beta-alkyl ethers may be encountered as artifacts in analyses of sterol mixtures from mamalian tissues.
