Formation of spiroiminodihydantoin nucleoside from 8-oxo-7,8-dihydro-2′-deoxyguanosine by nitric oxide under aerobic conditions

When 8-oxo-7,8-dihydro-2′-deoxyguanosine in potassium phosphate buffer of pH 7.4 was bubbled by nitric oxide at room temperature under aerobic conditions, two major products were formed. They were identified as the diastereomers of spiroiminodihydantoin deoxyribonucleoside on the basis of their identical ESI-MS and UV spectra and HPLC retention times with those of the major products in reaction of 8-oxo-7,8-dihydro-2′-deoxyguanosine with hypochlorous acid. A 1000-fold excess of 2′-deoxyguanosine did not inhibit the reaction of 8-oxo-7,8-dihydro-2′-deoxyguanosine with nitric oxide. The results suggest that an 8-oxo-7,8-dihydroguanine moiety formed in DNA may react with nitric oxide in the presence of oxygen molecule generating spiroiminodihydantoin in humans.

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