title: Characterization and reactivity of photodimers of dihydroneopterin and dihydrobiopterin.
abstract: 7,8-Dihydrobiopterin (H(2)Bip) and 7,8-dihydroneopterin (H(2)Nep) belong to a class of heterocyclic compounds present in a wide range of living systems. H(2)Bip accumulates in the skin of patients suffering from vitiligo, whereas H(2)Nep is secreted by human macrophages when the cellular immune system is activated. We have investigated the photochemical reactivity of both compounds upon UV-A irradiation (320-400 nm), the chemical structures of the products and their thermal stability. The study was performed in neutral aqueous solutions. The reactions were followed by UV/Visible spectrophotometry and HPLC and the products were analyzed by means of electrospray ionization mass spectrometry and (1)H-NMR. Excitation of H(2)Bip and H(2)Nep leads to the formation, in each case, of two main isomeric dimers. The latter compounds undergo a thermal process that may consist in a retro [2 + 2]-cycloaddition and hydrolysis to yield the reactant (H(2)Bip or H(2)Nep) and a product that has incorporated a molecule of H(2)O.
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET, Casilla de Correo 16, Sucursal 4, (1900) La Plata, Argentina.
authors.forename: Mariana
authors.initials: M
authors.lastname: Vignoni
authors.forename: Carolina
authors.initials: C
authors.lastname: Lorente
authors.forename: Franco M
authors.initials: FM
authors.lastname: Cabrerizo
authors.forename: Rosa
authors.initials: R
authors.lastname: Erra-Balsells
authors.forename: Esther
authors.initials: E
authors.lastname: Oliveros
authors.forename: Andrés H
authors.initials: AH
authors.lastname: Thomas
mesh_terms: D001708:Biopterins / Q000031:analogs & derivatives* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D019281:Dimerization; D006801:Humans; D007536:Isomerism; D008264:Macrophages / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D019798:Neopterin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D010782:Photolysis; D021241:Spectrometry, Mass, Electrospray Ionization; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: C000976:7,8-dihydroneopterin; D001708:Biopterins; D019798:Neopterin; C017226:7,8-dihydrobiopterin