An ESR study of the nitroxide radical of pentastarch-conjugated deferoxamine

Free Radic Biol Med. 1990;9(3):211-8. doi: 10.1016/0891-5849(90)90030-m.

Abstract

At higher concentrations, deferoxamine (DFO) reacts with hydroxyl radicals to produce a stable nitroxide free radical. Formation and decay of this nitroxide radical was investigated and compared with a novel modified pentastarch conjugate of DFO (MPS-DFO). Photolytic generation of hydroxyl radicals from H2O2 in the presence of free DFO produced a nitroxide radical with coupling constants of aN = 8.0 G and aH = 6.5 G. Under the same experimental conditions, equimolar concentrations of MPS-DFO produced an ESR signal of reduced intensity while iron-saturated MPS-DFO produced no signal. Incubation of free DFO with pentastarch (i.e., without conjugation) greatly decreased the intensity of the nitroxide radical signal. Using a spin-trapping technique with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), the pentastarch vehicle was shown to inhibit the DMPO-OH adduct formation. The decay of the DFO nitroxide radical decayed with a second-order rate constant while that of MPS-DFO decayed with a first-order rate constant. Thus, a novel derivative of DFO may provide some additional benefit in limiting DFO nitroxide radical formation and might explain the reported reduced in vivo toxicity of MPS-DFO relative to free DFO.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Deferoxamine / metabolism*
  • Deoxyribose / metabolism
  • Electron Spin Resonance Spectroscopy
  • Free Radical Scavengers
  • Hydrogen Peroxide / metabolism
  • Hydrolysis
  • Hydroxides
  • Hydroxyl Radical
  • Nitrogen Oxides / metabolism*

Substances

  • Free Radical Scavengers
  • Hydroxides
  • Nitrogen Oxides
  • Hydroxyl Radical
  • Deoxyribose
  • Hydrogen Peroxide
  • nitroxyl
  • Deferoxamine