Ageing and free radical formation. A biochemical approach to evaluate the efficacy of cosmetic preparations.

Synopsis A new method is described for studying the in vivo formation of oxygen reactive species (free radicals) in humans after exposure to UV radiation. The procedure is based on the quantitative determination in urine of (i) metabolic products of pentane, a hydrocarbon formed during lipid peroxidation, and (ii) thymine hydroxylated bases and deoxyribonucleosides as indices of DNA repair that has taken place. Creams containing UV filters protect the organism against free radical formation. Subjects using such cosmetic preparations during complete body tanning sessions do, in fact, have reduced urinary excretion of 2-pentanol and hydroxythmine derivatives.