Reduction kinetics and electrochemistry of tetracarboxylate nitroxides

Shengdian Huang, Hui Zhang, Joseph T. Paletta, Suchada Rajca, Andrzej Rajca

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Tetracarboxylate pyrroline nitroxides undergo very fast reduction with ascorbate/glutathione (GSH), with second-order rate constants that are five orders of magnitude greater than those for gem-diethyl pyrroline nitroxides. For tetracarboxylate nitroxides, the electrochemical reduction potentials, measured by square wave voltammetry, are much less negative (by about 0.8 V), compared with the corresponding gem-diethyl nitroxides, while the oxidation potentials become more positive (by about 0.7 V). Electrochemical potentials correlate well via simple regressions with field/inductive parameters such as Swain/Lupton F-parameters (and/or Charton σI-parameters). Rates of reduction with ascorbate/GSH similarly correlate well for four pyrroline nitroxides, except for the slowest reducing gem-diethyl nitroxide. These results suggest that the electron withdrawing groups adjacent to the nitroxide moiety have a strong accelerating impact on the reduction rates, and thus they are not suitable for the design of hydrophilic nitroxides for in vivo applications.

Original languageEnglish (US)
Pages (from-to)1-8
Number of pages8
JournalFree Radical Research
DOIs
StateAccepted/In press - Feb 22 2018

Fingerprint

Electrochemistry
Gems
Kinetics
Glutathione
Voltammetry
Electrons
Rate constants
Oxidation
pyrroline

Keywords

  • Electrochemistry
  • electron paramagnetic resonance
  • Hammett correlation
  • nitroxide
  • voltammetry

ASJC Scopus subject areas

  • Biochemistry

Cite this

Reduction kinetics and electrochemistry of tetracarboxylate nitroxides. / Huang, Shengdian; Zhang, Hui; Paletta, Joseph T.; Rajca, Suchada; Rajca, Andrzej.

In: Free Radical Research, 22.02.2018, p. 1-8.

Research output: Contribution to journalArticle

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AU - Rajca, Andrzej

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AB - Tetracarboxylate pyrroline nitroxides undergo very fast reduction with ascorbate/glutathione (GSH), with second-order rate constants that are five orders of magnitude greater than those for gem-diethyl pyrroline nitroxides. For tetracarboxylate nitroxides, the electrochemical reduction potentials, measured by square wave voltammetry, are much less negative (by about 0.8 V), compared with the corresponding gem-diethyl nitroxides, while the oxidation potentials become more positive (by about 0.7 V). Electrochemical potentials correlate well via simple regressions with field/inductive parameters such as Swain/Lupton F-parameters (and/or Charton σI-parameters). Rates of reduction with ascorbate/GSH similarly correlate well for four pyrroline nitroxides, except for the slowest reducing gem-diethyl nitroxide. These results suggest that the electron withdrawing groups adjacent to the nitroxide moiety have a strong accelerating impact on the reduction rates, and thus they are not suitable for the design of hydrophilic nitroxides for in vivo applications.

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