Protection against endogenous and UVB-induced oxidative damage in stratum corneum lipids by an antioxidant-containing cosmetic formulation

A 16-week human clinical study was carried out to determine the ability of antioxidants in a cosmetic vehicle to inhibit the induction of lipid peroxi dation in stratum corneum lipids. The study consisted of a twice daily appl ication of material for 12 weeks followed by a 4-week regression phase. Str atum corneum lipids were collected and then exposed to 500 mJ/cm(2) of ultr aviolet B (UVB) radiation in order to avoid excessive erythemal damage to t he subjects. Lipid peroxides were assayed by a methylene blue derivative as say and expressed per unit area of skin. During the treatment period, decre ases in the level of lipid peroxides were observed on the sites treated wit h the compositions containing antioxidants, as compared to the untreated si tes, and expressed as percent differences. Decreases were observed in endog enous as well as UV-induced lipid peroxides followed by a return to baselin e levels. These results demonstrate that antioxidants in a topical cosmetic formulation were effective in protecting human stratum corneum lipids agai nst endogenous oxidation or if challenged by 500 mJ/cm(2) UVB.