Chemical and photochemical reactivity of 6-hydroxymethyl-7,8-dihydropterin in aqueous solutions

Abstract

6-Hydroxymethyl-7,8-dihydropterin (H2Hmp) is an intermediate in the biosynthesis of folate, a precursor of coenzymes involved in the metabolism of nucleotides and amino acids. In this work, we have investigated the reactions undergone by H2Hmp in aqueous solutions at physiological pH, in the absence and in the presence of UV-A radiation (320–400 nm). In air-equilibrated solutions, H2Hmp undergoes slow thermal oxidation (half-life 37 h) to yield 7,8-dihydroxanthopterin (H2Xap) as the main product. The reaction of H2Hmp with hydrogen peroxide also yields H2Xap as a main product. In contrast, UV-A excitation of H2Hmp leads to the formation of a dimer identified by electrospray ionization mass spectrometry. The corresponding quantum yield of H2Hmp consumption (Φ−R) was independent of O2 and reactant concentration and has a value of 0.10 (±0.02), more than twice higher than that measured for other 6-subtituted 7,8-dihydropterins. Copyright © 2012 John Wiley & Sons, Ltd.