P-85 - Acceleration of UV induced thymidine dimer formation by salicylic acid

Abstract

UV light can induce thymine dimers in DNA, which is the main cause of skin cancer. Salicylic acid (o-hydroxybenzoic acid) is used as an exfoliator and added to various liquid cosmetics. It has been reported that salicylic acid is not a photosensitizer and shows no phototoxicity. When UV light from a high-pressure mercury lamp (200 W) with longer wavelength of 300 nm was irradiated on a neutral solution of four nucleosides (dC, dG, dT, and dA), no reaction was observed. However, addition of salicylic acid to the solution greatly accelerated the reaction of thymidine. The UV light irradiation to thymidine solution in the presence of salicylic acid resulted in four product peaks in HPLC. All the products were identified as isomers of thymidine cyclobutane dimer by MS and NMR. The thymidine cyclobutane dimers are generated from thymidine almost exclusively. The thymidine dimers formed in the most significant quantity are the cis-syn isomers. The present study indicates that salicylic acid accelerates the reaction of thymidine by UV light with longer wavelength of 300 nm forming thymidine dimers and suggests that salicylic acid may induce skin cancers in humans. Salicylic acid is a photosensitizer for the formation of thymidine dimers from thymidine by UV light.