The Reduction of a Nitroxide Spin Label as a Probe of Human Blood Antioxidant Properties

Saphier, Oshra; Silberstein, Tali; Shames, Alexander I.; Likhtenshtein, Gertz I.; Maimon, E; Mankuta, David; Mazor, Marija; Katz, M.L.; Meyerstein, Dan; Meyerstein, Naomi

doi:10.1080/1071576021000050410

Cited by 32 publications

(27 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Steady-state concentrations of the ascorbate radical in the blood [41,42] may significantly exceed those for superoxide radical particularly it is increased up to 3-30 nM during vitamin C supplementation. Therefore, the observed high reactivity of the cyclic HA towards ascorbate radical may significantly contribute in the observed kinetics of both the NR reduction [11] and HA oxidation [15] measured in blood as well as in the tissues with high ascorbate content such as liver and kidney [2,18,19].…”

Section: Discussionmentioning

confidence: 99%

“…Ascorbate plays significant role in NR reduction in erythrocytes, hepatocytes and kidney cells [2,18,19], which are rich in this compound. The reduction rates of NR by ascorbate normally correlate with its electrochemical reduction potential [20] and depend on nature of the radical ring [4,[19][20][21], charge of the radical [1,19], and steric shielding of nitroxyl fragment [22][23][24].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Reversible reduction of nitroxides to hydroxylamines: Roles for ascorbate and glutathione

Bobko

Kirilyuk

Grigor'ev

et al. 2007

Free Radical Biology and Medicine

134

123

View full text Add to dashboard Cite

Biological applications of stable nitroxyl radicals, NR, include their use as contrast agents for magnetic resonance imaging, spin labels, superoxide dismutase mimics, and antioxidants. The rapid reduction of NR in biological samples into hydroxylamines, HA, significantly limits their application. In its turn, reoxidation of HA back to the NR has been used for detection of reactive oxygen species, ROS. In this work comparative studies of the reduction of pyrrolidine, imidazoline and imidazolidine NR by ascorbate were performed taking advantage of recently synthesized tetraethyl substituted NR with much higher stability towards reduction both in vitro and in vivo. Surprisingly, these NR kept 10-50% of initial intensity of electron paramagnetic resonance signal for about 1 h in the presence of hundred fold excess of ascorbate. To explain this data, reoxidation of the corresponding HA by ascorbate radical and dehydroascorbic acid back to the NR was proposed. This hypothesis was supported by direct measurement of the NR appearance from the HA upon ascorbate radical generation by ascorbate oxidase, or in the presence of the dehydroascorbic acid. The reversible reaction between NR and ascorbate was observed for the various types of the NR, and the rate constants for direct and reverse reactions were determined. The equilibrium constants for oneelectron reduction of the tetraethyl substituted NR by ascorbate were found to be in the range from 2.65×10 −6 to 10 −5 which is significantly lower than corresponding values for the tetramethyl substituted NR (less or about 10 −4 ). This explains an establishment of EPR-detectable quasiequilibrium level of tetraethyl substituted NR in the presence of excess of ascorbate. The redox reactions of the NR-HA couple in ascorbate containing medium was found to be significantly affected by glutathione, GSH. This effect was attributed to the reduction of ascorbate radical by GSH, and the rate constant of this reaction was found to be equal to 10 M −1 s −1 . In summary, the data provide new insight into the redox chemistry of NR and HA, and significantly affect interpretation and strategy of their use as redox-and ROS-sensitive probes, or as antioxidants.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Reversible reduction of nitroxides to hydroxylamines: Roles for ascorbate and glutathione

Bobko

Kirilyuk

Grigor'ev

et al. 2007

Free Radical Biology and Medicine

134

123

View full text Add to dashboard Cite

show abstract

“…Upon reaction with superoxides, nitroxides undergo one-electron oxidation and subsequent two-electron reduction with reductants, which is driven forward by the redox potential of the nitroxide redox couple (Krishna et al, 1992). Conversely, nitroxides are reduced by ascorbic acid and converted into hydroxylamines (Saphier et al, 2003). This effect is one of the limitations of using nitroxides for monitoring in vivo redox status because the lifetime in vivo is shortened.…”

Section: Common Reactivity Of Nitroxidesmentioning

confidence: 96%

Synthesis and Utilization of α-Substituted Nitroxides

Yamasaki

Mito

Matsuoka³

et al. 2012

Nitroxides - Theory, Experiment and Applications

View full text Add to dashboard Cite

“…Ascorbic acid plays a significant role in the nitroxyl radical reduction in erythrocytes, hepatocytes, and kidney cells, which are rich in this compounds [16,17]. Ascorbic acid is one of the primary reducing agent in biochemistry, which is directly involved in many biochemical processes, such as metabolic-oxidation-reduction, carcinogensis, and aging.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study of the Reduction Process of Different Ring Structured Nitroxyl Spin Probes: An Electron Spin Resonance Study

Meenakumari¹

2016

EJB

View full text Add to dashboard Cite

Electron spin resonance spectroscopy (ESR) studies on the reduction process of nitroxyl spin probes were carried out for 1mM concentration of 14 N-labeled pyrrolidine nitroxyl spin probes, 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl (carbamoyl-PROXYL) and 3-carboxy-2,2,5,5-tetramethyl-pyrrolidine -1-oxyl (carboxy-PROXYL), 14 N-labeled piperidine nitroxyl spin probes, 4-methoxy-2,2,6,6-tetramethyl-piperidine-1-oxyl (methoxy-TEMPO) and 4-acetamido-2,2,6,6-tetramethyl-piperidine-1-oxyl (acetamido-TEMPO) in 1 mM concentration of ascorbic acid as a function of time. The half-life time and decay rate were estimated. The piperidine nitroxyl spin probes show a short half-life time compared with that of pyrrolidine nitroxyl spin probes. This result indicates that the higher stability of pyrrolidine nitroxyl spin probes. The ESR was also recorded for 1mM concentration of pyrrolidine nitroxyl spin probes and piperidine nitroxyl spin probes in pure water using X-band ESR spectrometer. The ESR parameters such as line width, hyperfine coupling constant, g-factor, signal intensity ratio and rotational correlation time were determined. These results indicate that the pyrrolidine nitroxyl spin probes have narrow line width and fast tumbling compared with the piperidine nitroxyl spin probes. Therefore, this study reveals that the pyrrolidine nitroxyl spin probes can act as good redox sensitive spin probes for free radical imaging.

show abstract

The Reduction of a Nitroxide Spin Label as a Probe of Human Blood Antioxidant Properties

Cited by 32 publications

References 12 publications

Reversible reduction of nitroxides to hydroxylamines: Roles for ascorbate and glutathione

Reversible reduction of nitroxides to hydroxylamines: Roles for ascorbate and glutathione

Synthesis and Utilization of α-Substituted Nitroxides

Comparative Study of the Reduction Process of Different Ring Structured Nitroxyl Spin Probes: An Electron Spin Resonance Study

Contact Info

Product

Resources

About