Reaction of thymidine and ascorbic acid induced by UV in the presence of salicylic acid.

When a neutral solution of thymidine and ascorbic acid was irradiated with UV light of wavelength longer than 300 nm in the presence of salicylic acid as a photosensitizer, six product peaks appeared in an HPLC chromatogram in addition to small amounts of thymidine dimers. The six products were identified as three pairs of diastereomers of 5-(2-deoxy-2-l-ascorbyl)-5,6-dihydrothymidine, 5-(2-l-ascorbyl)-5,6-dihydrothymidine, and 5,6-dihydrothymidine. These results suggest that novel DNA damage may be generated by ascorbic acid with salicylic acid induced by sunlight.