title: Photooxidation of pterin in aqueous solutions: biological and biomedical implications.
abstract: Studies of the photochemical reactivity of pterin (= 2-aminopteridin-4(3H)-one; PT) in acidic (pH 5.0-6.0) and alkaline (pH 10.2-10.8) aqueous solutions have been performed. The photochemical reactions were followed by UV/VIS spectrophotometry, thin layer chromatography (TLC), high-performance liquid chromatography (HPLC), and an enzymatic method for H2O2 determination. PT is not light-sensitive in the absence of molecular oxygen, but it undergoes photooxidation in the presence of O2, yielding several nonpteridinic products. The quantum yields for PT disappearance were found to be 8.2 (+/-0.6) x 10(-4) and 1.2 (+/-0.2) x 10(-3) in acidic and alkaline media, respectively. H2O2 was detected and quantified in irradiated solutions of PT; and its importance from a biomedical point of view is discussed. The rate constant of the chemical reaction between singlet oxygen ((1)O2) and PT was determined to be 2.5 (+/-0.2) x 10(5) l mol(-1) s(-1) in alkaline medium, and the role of (1)O2 in the photooxidation of pterin was evaluated.
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CONICET, CIC Casilla de Correo 16, Sucursal 4, 1900-La Plata, Argentina.
authors.forename: Franco M
authors.initials: FM
authors.lastname: Cabrerizo
authors.forename: María L
authors.initials: ML
authors.lastname: Dántola
authors.forename: Andrés H
authors.initials: AH
authors.lastname: Thomas
authors.forename: Carolina
authors.initials: C
authors.lastname: Lorente
authors.forename: André M
authors.initials: AM
authors.lastname: Braun
authors.forename: Esther
authors.initials: E
authors.lastname: Oliveros
authors.forename: Alberto L
authors.initials: AL
authors.lastname: Capparelli
mesh_terms: D010084:Oxidation-Reduction / Q000528:radiation effects; D010777:Photochemistry; D011622:Pterins / Q000378:metabolism* / Q000528:radiation effects*; D012996:Solutions / Q000378:metabolism / Q000528:radiation effects; D014466:Ultraviolet Rays; D014867:Water / Q000378:metabolism*
chemical_list: D011622:Pterins; D012996:Solutions; D014867:Water