Antioxidant effect of naturally occurring xanthines on the oxidative damage of DNA bases

The repair of the oxidised radicals of adenine and guanosine by several nat urally occurring xanthines was studied. Each pair of DNA purine/xanthine wa s made to react with the sulphate radical and the decrease of the concentra tion of both compounds was measured by HPLC as a function of irradiation ti me. The results show that xanthine efficiently prevents the oxidation of th e two DNA purines, Theophyline and paraxanthine repair the oxidised radical of adenine but not the one from guanosine. Theobromine and caffeine do not show any protecting effect. An order of the oxidation potentials of all th e purines studied is proposed.