Radical oxidation reactions of the purine moiety of 2'-deoxyribonucleosides and DNA by iron-containing minerals.

The radical oxidation capability of several classes of iron minerals, including biotite, hematite, magnetite, minette, nemalite, pyrite, vivianite and two chrysotiles (asbestos), was investigated by using a double experimental approach. One involved the electron spin resonance spin-trapping measurement of organic radicals obtained by the reaction of activated oxygen species, released upon incubation of the minerals in phosphate buffered solutions with formate used as the target molecule. In addition, the formation of mineral-mediated oxidation purine decomposition products, including 7,8-dihydro-8-oxo-2'-deoxyguanosine and 7,8-dihydro-8-oxo-2'-deoxyadenosine, was searched within nucleosides and DNA by using specific and sensitive HPLC electrochemical assays. Emphasis was placed on the mechanistic aspects of the radical oxidation reactions involved in the formation of the two C(8) hydroxylated purine decomposition products.