Document Detail

Reactions of the NO redox forms NO+, *NO and HNO (protonated NO-) with the melatonin metabolite N1-acetyl-5-methoxykynuramine.
MedLine Citation:
PMID:  17910607     Owner:  NLM     Status:  MEDLINE    
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.
Rüdiger Hardeland; Claudia Backhaus; Azadeh Fadavi
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of pineal research     Volume:  43     ISSN:  0742-3098     ISO Abbreviation:  J. Pineal Res.     Publication Date:  2007 Nov 
Date Detail:
Created Date:  2007-10-03     Completed Date:  2008-02-26     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8504412     Medline TA:  J Pineal Res     Country:  Denmark    
Other Details:
Languages:  eng     Pagination:  382-8     Citation Subset:  IM    
Johann Friedrich Blumenbach Institute of Zoology and Anthropology, University of Göttingen, Göttingen, Germany.
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MeSH Terms
Hydrogen-Ion Concentration
Kynuramine / analogs & derivatives*,  chemistry
Melatonin / chemistry*,  metabolism
Nitric Oxide Donors / chemistry
Nitrites / chemistry
Nitro Compounds / chemistry*
Nitrogen Oxides / chemistry
Reactive Nitrogen Species / chemistry
Reg. No./Substance:
0/Nitric Oxide Donors; 0/Nitrites; 0/Nitro Compounds; 0/Nitrogen Oxides; 0/Reactive Nitrogen Species; 363-36-0/Kynuramine; 52450-39-2/N-acetyl-5-methoxy kynurenamine; 73-31-4/Melatonin

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