948-60-7Relevant articles and documents
Photochemistry of 6-formylpterin in alkaline medium
Thomas, Andres H.,Suarez, Gustavo,Cabrerizo, Franco M.,Capparelli, Alberto L.
, p. 3849 - 3860 (2001)
6-formylpterin solutions at pH 11 were photolyzed at 350 nm at room temperature. The photochemical reactions were followed by UV/VIS spectrophotometry, thin layer chromatography (TLC), and high-performance liquid chromatography (HPLC). In the presence of oxygen, 6-carboxypterin is the only photoproduct detected by the analytical techniques mentioned. In the absence of oxygen, a new compound showing an absorbance maximum at 480 nm is observed. The latter compound is thermally oxidized very fast in the presence of oxygen to 6-carboxypterin. The quantum yields of substrate disappearance and of photoproduct formation are reported.
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Dion,Loo
, p. 1857,1858 (1961)
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Hazlett,Kildsig
, p. 570,571 (1970)
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Effect of pterin impurities on the fluorescence and photochemistry of commercial folic acid
Dántola, M. Laura,Urrutia, M. Noel,Thomas, Andrés H.
, p. 157 - 163 (2018/03/24)
Folic acid, or pteroyl?L?glutamic acid (PteGlu) is a conjugated pterin derivative that is used in dietary supplementation as a source of folates, a group of compounds essential for a variety of physiological functions in humans. Photochemistry of PteGlu is important because folates are not synthesized by mammals, undergo photodegradation and their deficiency is related to many diseases. We have demonstrated that usual commercial PteGlu is unpurified with the unconjugated oxidized pterins 6?formylpterin (Fop) and 6?carboxypterin (Cap). These compounds are in such low amounts that a normal chromatographic control would not detect any pterinic contamination. However, the fluorescence of PteGlu solutions is due to the emission of Fop and Cap and the contribution of the PteGlu emission, much lower, is negligible. This is because the fluorescence quantum yield (ΦF) of PteGlu is extremely weak compared to the ΦF of Fop and Cap. Likewise, the PteGlu photodegradation upon UV-A radiation is an oxidation photosensitized by oxidized unconjugated pterins present in the solution, and not a process initiated by the direct absorption of photons by PteGlu. In brief, the fluorescence and photochemical properties of PteGlu solutions, prepared using commercially available solids, are due to their unconjugated pterins impurities and not to PteGlu itself. This fact calls into question many reported studies on fluorescence and photooxidation of this compound.
Photochemistry of dihydrobiopterin in aqueous solution
Vignoni, Mariana,Cabrerizo, Franco M.,Lorente, Carolina,Claparols, Catherine,Oliveros, Esther,Thomas, Andres H.
experimental part, p. 800 - 810 (2010/06/20)
Dihydrobiopterin (H2Bip) and its oxidized analogue, biopterin (Bip), accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder in which the protection against UV radiation fails. The photochemistry of H2Bip was studied in neutral aqueous solutions upon UV-A irradiation (320-400 nm) at room temperature. The photochemical reactions were followed by UV/vis spectrophotometry, HPLC and enzymatic methods for hydrogen peroxide (H2O2) determination. Photoproducts were analyzed by means of electrospray ionization mass spectrometry. Under anaerobic conditions, excitation of H2Bip leads to the formation of at least two isomeric dimers with molecular masses equal to exactly twice the molecular mass of the reactant. This reaction takes place from the singlet excited state of the reactant. To the best of our knowledge, this is the first time that the photodimerization of a dihydropterin is reported. In the presence of air, the dimers are again the main photoproducts at the beginning of the reaction, but a small proportion of the reactant is converted into Bip. As the reaction proceeds and enough Bip accumulates in the solution, a photosensitized process starts, where Bip photoinduces the oxidation of H2Bip to Bip, and H 2O2 is formed. As a consequence, the rates of H 2Bip consumption and Bip formation increase as a function of irradiation time, resulting in an autocatalytic photochemical process. In this process, Bip in its triplet excited state reacts with the ground state of H 2Bip. The mechanisms involved are analyzed and the biological implications of the results are discussed. The Royal Society of Chemistry 2010.
