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 language | English (US) |
---|---|
Pages (from-to) | 327-334 |
Number of pages | 8 |
Journal | Free Radical Research |
Volume | 52 |
Issue number | 3 |
DOIs | |
State | Published - Mar 4 2018 |
Keywords
- Electrochemistry
- Hammett correlation
- electron paramagnetic resonance
- nitroxide
- voltammetry
ASJC Scopus subject areas
- Biochemistry