Damaged products of cytosine in hydroxyl radical solution under UV-irradiation

Modification of cytosine in hydrogen peroxide solution by UV-irradiation was investigated. Hydroxyl radicals generated from H2O2 under W irradiation oxidized cytosine to the monohydroxy and dihydroxy derivatives at the C5-C6 double bond. Several deamination products of modified cytosine derivative were also observed. Moreover, further transformation/rearrangement of some modified bases led to the formation of five-membered ring derivatives such as 5-hydroxyhydantoin and 3-amino-4,5-dihydroxypyrazole. Various products resulting from radical interaction with cytosine were identified by using gas chromatography/mass spectrometry (GC/MS) after trimethylsilylation derivatization, Some products were identified by comparing their retention time and mass spectra with those of synthetic compounds that were formed by the treatment of cytosine with OsO4. Major products were quantified by GC/MS-selected ion monitoring mode. Some of products including uracil glycol were significantly decomposed during formic acid hydrolysis. (C) 2001 Elsevier Science B.V. All rights reserved.