OXIDATIVE DAMAGE OF HUMAN SKIN LIPIDS - DEPENDENCE OF LIPID-PEROXIDATION ON STEROL CONCENTRATION

Photoprotection against sunburn and associated irradiation-induced dam ages of the human skin is mainly attributed to the darkening of the bi ochrome melanin by its oxidation. Human skin lipids were examined for an additional protection by sterols. Lipid vesicles prepared from extr acted human skin lipids as well as from mixtures of typical lipids of the stratum corneum were irradiated by UV light in the presence and ab sence of oxygen. The oxidative degradation of various lipids was measu red by quantitative HPTLC, by the dichlorofluorescein fluorescent assa y, by the thiobarbituric acid assay and a novel luminol-based chemilum inescence technique. Electron spin resonance was used to look for cert ain radical intermediates, The results indicate, that sterols, mainly free cholesterol, with their high concentration in the Lipid barrier o f the stratum corneum (up to 50 mol%) effectively compete with the per oxidation of other human skin lipids (ceramides and free fatty acids). (C) 1997 Elsevier Science B.V.