Photoinduced Formation of Reactive Oxygen Species by the Acid Form of 6-(Hydroxymethyl)pterin in Aqueous Solutions

ANDRÉS H. THOMAS; ROMINA CABRERIZO; MARIANA VIGNONI; ROSA ERRA-BALSELLS; FRANCO M. CABRERIZO; ALBERTO L. CAPPARELLI

HELVETICA CHIMICA ACTA

Wiley-VCH

Año: 2006 vol. 89 p. 1090 - 1104

0018-019X

Studies of the photochemistry of 6-(hydroxymethyl)pterin (HPT) in acidic aqueous solutions (pH 5.0 - 6.0) at 350 nm and room temperature have been performed. The photochemical reactions were followed by UV-VIS spectrophotometry, thin layer chromatography (TLC), high performance liquid chromatography (HPLC) and enzymatic methods for superoxide anion radical (O2•-) and hydrogen peroxide (H2O2) determination. When HPT is exposed to UV-A radiation intermediates are formed that react with O2 to yield 6-formylpterin (FPT) and 6-carboxypterin (CPT). O2•- and H2O2 are generated during photooxidation of HPT. The quantum yields of HPT disappearance and of photoproducts formation are reported. HPT has been also investigated for its efficiency of singlet oxygen (1O2) production in acidic aqueous solution. The quantum yield of 1O2 production (FD = 0.15 ± 0.02) has been determined by measurements of the 1O2 luminescence in the near-infrared (1270 nm) upon continuous excitation of the sensitizer. However, 1O2 does not participate in the photooxidation of HPT to FPT and CPT.