Photosensitization and photoprotection properties of nicotinic acid derivatives

The photosensitizing action of nicotinic acid, nicotinamide, and nicotinehydroxymethylamide on the photooxidation of glycyltryptophan (Gly-Trp) in an aqueous solution using UV light (240–410 nm) was found. The photooxidation was monitored by measuring chemiluminescence (CL) resulting from the decay of one of the oxidation products, dioxethane. The photosensitizing action decreases in the following sequence: nicotinamide > nicotine-hydroxymethylamide > nicotinic acid. The addition of benzoquinone (0.01 mmol L⁻¹) results in a substantial decrease in the yield of sensitized CL, which indicates that the superoxide radical anion participates in the photooxidation. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 942–945, May, 1997.