SOD-Like Activity of 5-Membered Ring Nitroxide Spin Labels

  • Amram Samuni
  • Ahn Min
  • C. Murali Krishna
  • James B. Mitchell
  • Angelo Russo
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 264)


Although Superoxide anion mediated redox reactions have been extensively studied, only a few studies involving radical-radical reactions of Superoxide with nitroxides have been so far reported1–8. Superoxide can act as a one-electron reductant with many species, including the biochemical and toxicological interesting reactions with ferricytochrome c9, tetranitromethane10, or nitroblue-tetrazolium11. Oxidation reactions involving Superoxide are less common and usually involve complex multi-electron steps such as oxidation of sulfite or epinephrine12 where O 2 may serve as an initiator and propagator of free radical chain reactions. One of the few one-electron oxidations mediated by O 2 is the conversion of secondary hydroxylamines into nitroxides1. The hydroxylamine, 2-ethyl-l-hydroxy-2,5,5 trimethyl-3-oxazolidine (OXANOH), is readily oxidized by O 2 to a stable radical, 2-ethyl 2,5,5-trimethyl-3-oxazolidinoxyl (OXANO) and this oxidation has been employed to detect and assay Superoxide2. Recently O 2 has been found to also be capable of reducing OXANO to OXANOH13. Through the combined reduction and oxidation of O 2 , the OXANO / OXANOH couple exhibited a Superoxide dismutase-like activity13. This low molecular weight, cell permeable, non-immunogenic, non-cytotoxic, metal-independent SOD-mimic was found, in the present study, to protect mammalian cells against oxidative damage. To determine if other nitroxides have similar properties we investigated a series of nitroxide derivatives for their reactions with O 2 by using electron spin resonance spectrometry. The 5-membered ring nitroxides were reduced by O 2 to the corresponding hydroxylamines, which in turn were re-oxidizable to the parent nitroxides. The results indicate that SOD-like activity is not limited to OXANO but is shared by nitroxide spin-labels in general.


Xanthine Oxidase Free Radical Chain Reaction Stable Nitroxides Milk Xanthine Oxidase Ring Nitroxides 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Plenum Press, New York 1990

Authors and Affiliations

  • Amram Samuni
    • 2
  • Ahn Min
    • 1
  • C. Murali Krishna
    • 1
  • James B. Mitchell
    • 1
  • Angelo Russo
    • 1
  1. 1.Radiation Oncology Branch, Clinical Oncology Program, Division of Cancer Treatment, N.C.I.National Institutes of HealthBethesdaUSA
  2. 2.Molecular BiologyHebrew University Medical SchoolJerusalemIsrael

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