Comparative sugar degradation by (OH)^· produced by the iron-driven fenton reaction and gamma radiolysis

We compared the attack of deoxyribose and mannitol by (OH)^· produced by gamma radiolysis or the iron-driven Fenton reaction. Deoxyribose (DR) oxidation by gamma radiolysis gave rise to thiobarbituric reactive substances (TBARS) with a yield of 17 mol (OH)^· per mole of TBARS. (OH)^· scavengers (benzoate, formate, and pentoxifylline) protected DR from oxidation. Mannitol was similarly oxidized by (OH)^· produced by gamma radiolysis, with a yield of 14 mol (OH)^· per mole of TBARS produced. A mixture containing both DR and mannitol gave rise to TBARS production with a yield of 9 mol (OH)^· per mole of TBARS superior to that of each product separately, suggesting the formation of secondary radicals responsible for the degradation of DR or mannitol. When (OH)^· was produced by the iron-driven Fenton reaction, DR gave rise to TBARS whereas mannitol did not. Furthermore, mannitol protected DR against degradation, apparently in the same way as desferrioxamine and diethylenetriaminepentaacetic acid, suggesting that it acts as an iron chelator. It can thus be assumed that, according to the site of (OH)^· production, sugar molecules are degraded as a function of their rate constant with (OH)^· or their iron chelating capacity.