HYDROXYLATION OF ADENINE AND ITS DERIVATIVES BY RADIOMETRIC AGENTS

A comparative study of the hydroxylation of adenine by hydrogen peroxyde has been performed under UV radiation and in the presence of ascorbic acid and hydrogen peroxyde. This was achieved by monitoring the formation of stable final products, namely 8-hydroxyadenine. In the first case, the hydroxylation proceeds via a radical mechanism, the hydroxylating agent being the OH. radical produced by UV-homolysis of hydrogen peroxyde. The formation of 8-hydroxyadenine was observed as well as a second compound which is unstable in aqueous solution. This compound should result from a further reaction of 8-hydroxyadenine itself with OH.. Using a mixture of hydrogen peroxyde and ascorbic acid, without irradiation, the formation of 8-hydroxyadenine was observed, but in this case the OH. radical is not involved, as it was concluded from spin-trapping experiments and by studying the effect of the presence of OH. scavengers. There is also no noticeable influence of light on the yield of 8-hydroxyadenine, and the effect of oxygen is opposite to the one observed in OH. induced hydroxylation of adenine. In the ascorbic acid-hydrogen peroxyde system, the first compound must act as a catalyst, the second one, being the actual hydroxylating active species.