Effect of ultraviolet on thiamine and thiamine disulfides

In a neutral medium, the exposure of thiamine disulfide to the ultraviolet of solar radiation (as well as to the ultraviolet radiation of mercury lamp with λ > 300 nm) results in the formation of a thiamine molecule with closed thiazole ring and a molecule of thiamine thiazolone. Asymmetric thiamine disulfides, e.g., thiamine propyl disulfide, on exposure to ultraviolet (UVA range) produced thiamine and propyl disulfides. Thiamine and thiazolone of thiamine are stable upon exposure to light of 320-400 nm (UVA range). UV irradiation within spectral range of 200-300 nm results in further photodestruction of thiamine and thiamine thiazolone and production of 2-methyl-4-amino-5aminomethyl-pyrimidine as the main photoproduct. The possibility to use thiamine disulfide derivatives as a promising class of anti-cataract drugs as well as drugs to decrease the toxic effect of ultraviolet radiation on human retina is discussed.