Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 7-Day Trial for You or Your Team.

Learn More →

Reactions of the NO redox forms NO + , • NO and HNO (protonated NO – ) with the melatonin metabolite N 1 ‐acetyl‐5‐methoxykynuramine

Reactions of the NO redox forms NO + , • NO and HNO (protonated NO – ) with the melatonin... Abstract: The different NO redox forms, NO+, •NO and HNO (= protonated NO–), were compared for their capabilities of interacting with the melatonin metabolite N1‐acetyl‐5‐methoxykynuramine (AMK), using NO+SbF6–, PAPA‐NONOate and Angeli’s salt as donors of the respective NO species. Particular attention was paid to stability and possible interconversions of the redox forms. •NO formation was followed by measuring the decolorization of 2‐(trimethylammonio‐phenyl)‐4,4,5,5‐tetramethyl‐imidazoline‐1‐oxyl‐3‐oxide (TMA‐PTIO), at different pH values, at which NO+ is, in aqueous solution, either highly unstable (pH 7.4) or relatively stable (pH 2.0). •NO donation by PAPA‐NONOate, as indicated by TMA‐PTIO decolorization, was similar at either pH and 3‐acetamidomethyl‐6‐methoxycinnolinone (AMMC) was formed as the major product from AMK, at pH 7.4 more efficiently than at pH 2.0. At pH 2.0, TMA‐PTIO decolorization by NO+SbF6– was much weaker than by PAPA‐NONOate, but AMMC was produced at substantial rates, whereas neither TMA‐PTIO decolorization nor AMMC formation was observed with the NO+ donor at pH 7.4. As NO+ is also stable in organic, especially aprotic solvents, NO+SbF6– was reacted with AMK in acetonitrile, ethanol, butanol, and ethyl acetate. In all these cases, AMMC was the only or major product. In ethyl acetate, N1‐acetyl‐5‐methoxy‐3‐nitrokynuramine (AMNK) was also formed, presumably as a consequence of organic peroxides emerging in that solvent. Presence of tert‐butylhydroperoxide in an ethanolic solution of NO+SbF6– and AMK also resulted in AMNK formation, in addition to AMMC and two red‐fluoresecent, to date unknown products. However, hydrogen peroxide enhanced •NO‐dependent AMMC production from AMK and also from N1‐acetyl‐N2‐formyl‐5‐methoxykynuramine. HNO donation by Angeli’s salt (Na2N2O3) also caused AMMC formation from AMK at pH 7.4, with a somewhat lower efficiency than PAPA‐NONOate, but no AMNK nor any other product was detected. Therefore, all three NO congeners are, in principle, capable of nitrosating AMK and forming AMMC, but in biological material the reaction with NO+ is strongly limited by the extremely short life‐time of this redox form. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Pineal Research Wiley

Reactions of the NO redox forms NO + , • NO and HNO (protonated NO – ) with the melatonin metabolite N 1 ‐acetyl‐5‐methoxykynuramine

Download PDF
7 pages

Loading next page...
 
/lp/wiley/reactions-of-the-no-redox-forms-no-no-and-hno-protonated-no-with-the-ulRKktMmzT

References (35)

Publisher
Wiley
Copyright
Copyright © 2007 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0742-3098
eISSN
1600-079X
DOI
10.1111/j.1600-079X.2007.00489.x
pmid
17910607
Publisher site
See Article on Publisher Site

Abstract

Abstract: The different NO redox forms, NO+, •NO and HNO (= protonated NO–), were compared for their capabilities of interacting with the melatonin metabolite N1‐acetyl‐5‐methoxykynuramine (AMK), using NO+SbF6–, PAPA‐NONOate and Angeli’s salt as donors of the respective NO species. Particular attention was paid to stability and possible interconversions of the redox forms. •NO formation was followed by measuring the decolorization of 2‐(trimethylammonio‐phenyl)‐4,4,5,5‐tetramethyl‐imidazoline‐1‐oxyl‐3‐oxide (TMA‐PTIO), at different pH values, at which NO+ is, in aqueous solution, either highly unstable (pH 7.4) or relatively stable (pH 2.0). •NO donation by PAPA‐NONOate, as indicated by TMA‐PTIO decolorization, was similar at either pH and 3‐acetamidomethyl‐6‐methoxycinnolinone (AMMC) was formed as the major product from AMK, at pH 7.4 more efficiently than at pH 2.0. At pH 2.0, TMA‐PTIO decolorization by NO+SbF6– was much weaker than by PAPA‐NONOate, but AMMC was produced at substantial rates, whereas neither TMA‐PTIO decolorization nor AMMC formation was observed with the NO+ donor at pH 7.4. As NO+ is also stable in organic, especially aprotic solvents, NO+SbF6– was reacted with AMK in acetonitrile, ethanol, butanol, and ethyl acetate. In all these cases, AMMC was the only or major product. In ethyl acetate, N1‐acetyl‐5‐methoxy‐3‐nitrokynuramine (AMNK) was also formed, presumably as a consequence of organic peroxides emerging in that solvent. Presence of tert‐butylhydroperoxide in an ethanolic solution of NO+SbF6– and AMK also resulted in AMNK formation, in addition to AMMC and two red‐fluoresecent, to date unknown products. However, hydrogen peroxide enhanced •NO‐dependent AMMC production from AMK and also from N1‐acetyl‐N2‐formyl‐5‐methoxykynuramine. HNO donation by Angeli’s salt (Na2N2O3) also caused AMMC formation from AMK at pH 7.4, with a somewhat lower efficiency than PAPA‐NONOate, but no AMNK nor any other product was detected. Therefore, all three NO congeners are, in principle, capable of nitrosating AMK and forming AMMC, but in biological material the reaction with NO+ is strongly limited by the extremely short life‐time of this redox form.

Journal

Journal of Pineal Research – Wiley

Published: Nov 1, 2007

There are no references for this article.