Original scientific paper

Reinvestigation of the Oxidation Properties of Nitroxides

Vesna Nothig-Laslo ; Chemistry Department, University of Cincinnati, Cincinnati, OH 45211 USA
Albert M. Bobst ; Chemistry Department, University of Cincinnati, Cincinnati, OH 45211 USA

Abstract

The rates of reduction of the two amino-nitroxides, 3-amino-2,2,5,5-te- tramethylpyrrolidine-l-oxyl (I) and 4-amino-2,2,6,6-tetramethylpiperidine-l- oxyl (JI) were compared. Reducing agents, /?-mercaptoethanol and sodium ascorbate, were freshly prepared in the presence of nitrogen or air, in a buffer consisting of 0.1 M Na-cacodylate, 0.01 M NaCl, pH 7.
Similar functions of the ESR signal decrease with time were detected for I and II with both reducing agents under nitrogen when the ratio of nitroxide molarity versus reducing agent molarity was kept the same for a given set of experiments. However, a significant difference in the ESR signal decrease with time was observed between I and II with ascorbate in the presence of air. Reproducible time dependence of the ESR signal decay required the use of freshly prepared reducing solutions.
Our results strongly suggest that at least amino substituted five and six- membered ring nitroxides oxidize electron donors at the same rate. The apparent greater stability of I versus II seems to be due to the slower reoxidation rate of the hydroxylamine of II as compared to the hydroxylamine of I. Thus, under in vivo conditions, I and II will become ESR silent at the same rate unless the tissue is not under anaerobic conditions.

Keywords

Hrčak ID:

137365

URI

https://hrcak.srce.hr/137365

Publication date:

30.6.1991.

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