DNA oxidation is the process of oxidative damage on Deoxyribonucleic Acid. It occurs most readily at guanine residues due to the high oxidation potential of this base relative to cytosine, thymine, and adenine. It is widely believed to be linked to certain disease and cancers.
More than 20 oxidatively damaged DNA base lesions were identified in 2003 by Cooke et al.[1] and these overlap the 12 oxidized bases reported in 1992 by Dizdaroglu.[2] Two of the most frequently oxidized bases found by Dizdaroglu after ionizing radiation (causing oxidative stress) were the two oxidation products of guanine shown in the Figure. One of these products was 8-OH-Gua (8-hydroxyguanine). (The article 8-Oxo-2'-deoxyguanosine refers to the same damaged base since the keto form 8-oxo-Gua described there may undergo a tautomeric shift to the enol form 8-OH-Gua shown here.) The other product was FapyGua (2,6-diamino-4-hydroxy-5-formamidopyrimidine). Another frequent oxidation product was 5-OH-Hyd (5-hydroxyhydantoin) derived from cytosine.

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