Visible-light photochemistry of 6-formyl-7,8-dihydropterin in aqueous solution

Pterins are a family of heterocyclic compounds present in a wide range of living systems and are involved in different photobiological processes. 6-Formyl-7,8-dihydropterin (H2Fop), is a product of oxidation of several natural occurring pterin derivatives, and its absorption spectrum presents as special feature an intense band in the visible region. Studies of the photochemistry of H2Fop in aqueous solutions under visible radiation and room temperature were performed. The photochemical reactions were followed by UV–vis spectrophotometry, electrochemical measurement of dissolved O2, enzymatic methods for H2O2 determination and HPLC. When H2Fop in air-equilibrated solution was exposed to light, O2 was consumed, the reactant was oxidized to 6-formylpterin (Fop), and H2O2 released. When the photolysis took place in the absence of O2, a red compound was generated. This product was rapidly oxidized to Fop on admission of O2. The quantum yields of H2Fop disappearance and of photoproducts formation are reported and the effect of pH is analyzed. The potential biological implications of the results obtained are also discussed.