- (2,5-Dioxoimidazolidin-4-ylidene)aminocarbonylcarbamic Acid as a Precursor of Parabanic Acid, the Singlet Oxygen-Specific Oxidation Product of Uric Acid
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Previously, we identified that parabanic acid (PA) and its hydrolysate, oxaluric acid (OUA), are the singlet oxygen-specific oxidation products of uric acid (UA). In this study, we investigated the PA formation mechanism by using HPLC and a time-of-flight mass spectrometry technique and identified unknown intermediates as (2,5-dioxoimidazolidin-4-ylidene)aminocarbonylcarbamic acid (DIAA), dehydroallantoin, and 4-hydroxyallantoin (4-HAL). DIAA is the key to PA production, and its formation pathway was characterized using 18O2 and H218O. Two oxygen atoms were confirmed to be incorporated into DIAA: the 5-oxo- oxygen from singlet oxygen and the carboxylic oxygen from water. Isolated DIAA and 4-HAL gave PA stoichiometrically. A plausible reaction scheme in which two pathways branch out from DIAA is presented, and the potential for PA as an endogenous probe for biological formation of singlet oxygen is discussed.
- Iida, Sayaka,Yamamoto, Yorihiro,Fujisawa, Akio
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- The sonolysis of uracil
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The sonolysis of uracil (1) has been studied at 630 kHz in the presence of air, oxygen, nitrogen and argon.The degradation products were identified by gc-ms analysis.Under aerated conditions the following products were found: uracil glycols (7), isobarbituric acid (8), N-formyl-N'-glyoxylurea (6), 5-hydroxyhydantoin (9), dialuric acid (10), alloxan monohydrate (12), parabanic acid (13), and oxaluric acid (14).In deaerated solutions 6, 13, and 14 were not observed but either 6-hydroxy-5,6-dihydrouracil (17) or its isomer (18) were detected in addition to 7, 8, 9, 10, and 12.The observed products have been used to develop a possible mechanism for the sonolytic degradation and the results are similar to those obtained in radiolysis.The sonolytic degradation of 5-bromouracil (19) is also reported: the products observed were 5-bromobarbituric acid (20), 12, 13, 14, and 9 and these can be rationalized by a similar mechanism scheme.
- Yu, Tain-Jen,Sutherland, Ronald G.,Verrall, Ronald E.
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p. 1909 - 1915
(2007/10/02)
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