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

✍ Scribed by Andrés H. Thomas; Romina Cabrerizo; Mariana Vignoni; Rosa Erra-Balsells; Franco M. Cabrerizo; Alberto L. Capparelli

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: German
• Weight: 153 KB
• Volume: 89
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.200690107

✦ Synopsis

Abstract

The photochemistry of 6‐(hydroxymethyl)pterin (HPT; 1) in aqueous solution (pH 5–6) was investigated by irradiation at 350 nm at room temperature. The photochemical reactions of the acidic form 1a were followed by UV/VIS spectrophotometry, thin‐layer chromatography (TLC), high‐performance liquid chromatography (HPLC), and enzymatic methods for the determination of the superoxide anion radical (O$\rm{_2^{ \bullet - } }$) and hydrogen peroxide (H~2~O~2~). When 1a is exposed to UV‐A radiation, the intermediates 4 and 4′ are formed reacting with O~2~ to yield 6‐formylpterin (FPT; 5) and 6‐carboxypterin (CPT; 6) under formation of O$\rm{_2^{ \bullet - } }$ and H~2~O~2~ (Scheme 3). The quantum yields of the disappearance of HPT (1a) and of the formation of the photoproducts 5 and 6 were determined. HPT was investigated for its efficiency in singlet‐oxygen (^1^O~2~) production in acidic aqueous solution. The corresponding quantum yield of ^1^O~2~ production (Φ~Δ~) was 0.15 ± 0.02, as measured by the ^1^O~2~ luminescence in the near‐IR (1270 nm) upon continuous excitation of the sensitizer. However, ^1^O~2~ does not participate in the actual photooxidation of HPT (1a) to FPT (5) and CPT (6).