Alloxan anion radical

Anionic radical ligand derived from alloxan D shows epr which are markedly affected by coordination to diamagnetic Mg, Ca and Zn + ions. 

Superoxide anion radicals (02 ) generated in alloxan diabetic rat brain tissue extracts incubated for 10 min at 25 °C with varying concentrations of xanthine (0.05,0.1,0.15, and 0.2 mM) plus xanthine oxidase (0.1. 0.2, 0.3, and 0.6 U/ml), caused a decrease in the cytosolic creatine kinase (EC 2.7.3.2) activities by 29, 50, 72, and 79 %, respectively (Genet et al. 2000). The addition of 80 pg/ml of superoxide dismutase (EC 1.15.1.1) reversed the depressed creatine kinase activities almost to control values. Hydrogen peroxide (0.001,0.01,0.1, and 1 mM) decreased the cytosolic creatine kinase activities by 5, 11, 20, and 40%, respectively. This decrease in creatine kinase activities was reversed significantly to control values when 10 p,g/ml of catalase (EC 1.11.1.6) was added to the reaction mixture during the incubation. 

Uric acid is present in human plasma at much higher levels than those encountered in other primates because the enzyme urate oxidase is absent from human tissues (Cutler 1984). it has therefor e been proposed that uric acid is an important antioxidant for humans (Ames et al. 1981). Urate reacts with peroxynitrite with an apparent second order rate constant of 4.8 x 10 M s in a complex process, which is accompanied by oxygen consumption and formation of allantoin, alloxan, and urate derived radicals (Santos et al. 1999). The main radical was identified as the aminocarbonyl radical by the electrospray mass spectra of its 5,5-dimethyl-/-pyrroline-N-oxide adduct. Mechanistic studies suggested that urate reacts with peroxynitrous acid and with the radicals generated from its decomposition to form products that can further react with peroxynitrite anion. 

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