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

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 À 2 ) 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 À 2 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 (

Photoinduced Generation of H2O2 and O2•- by 6-formylpterin in Aqueous Solutions

“…The photoreduction of Cyt in the absence of 02 has already been observed for other heterocyclic compounds in aqueous solutions (24). These results are similar to those reported for hydroxymethylpterin (26) and suggest that the red intermediate generated after irradiation of formylpterin is able to transfer one electron either to 02 to yield 02· or directly to Cyt. In air-equilibrated solutions where the 02 represents a large excess over Cyt, the first possibility happens.…”

Photophysics and Photochemistry of Pterins in Aqueous Solution

“…The accumulation of PTs derivatives in the skin of patients who suffer this disease has been confirmed as mentioned above. , Therefore, PTs might be involved in the pathogenesis of vitiligo in contributing to the production of significant levels of H 2 O 2 . It is noteworthy that the photolysis of the acid form of FPT yields CPT as the main photoproduct, instead of FPT (Scheme ) 4 Photochemistry of BPT, NPT, HPT, and FPT in Aqueous Solution …”

“…24 It is noteworthy that the photolysis of the acid form of FPT yields CPT as the main photoproduct, instead of FPT (Scheme 4). 25 The photochemistry of the PT moiety itself has been investigated using PT 26 and PT derivatives containing substituents that cannot be easily oxidized, e.g., CPT 27 and 6-methylpterin (MPT). 28 Acid and basic forms of the PT moiety are photostable in these cases in the absence of O 2 , whereas excitation in the presence of O 2 leads to oxidation, yielding nonpterinic photoproducts (cleavage of PT moiety) and H 2 O 2 .…”

Chemical and photochemical properties of chloroharmine derivatives in aqueous solutions

“…H 2 O 2 was quantified after reaction with 4-aminophenazone and phenol. 35,43 Briefly, 600 µl of irradiated solution (UVA) was added to 1.6 ml of reagent.…”