title: Electrochemical and spectroelectrochemical behavior of the main photodegradation product of nifedipine: the nitrosopyridine derivative.
abstract: OBJECTIVE
  To characterize the electrochemical behavior of the photodegradation product of nifedipine, i.e., 2,6-dimethyl-4-(2-nitrosophenyl)-3,5-pyridine-carboxylic acid dimethyl ester (NPD) in different electrolytic media. We also evaluated the interaction between free radicals generated from NPD and xeno/endobiotics.
  
  
  METHODS
  Tast polarography, differential pulse polarography, and cyclic voltammetry were used for the characterization. Controlled potential electrolysis and ultraviolet-visible spectroscopy were used to generate and to detect the nitroso radical anion.
  
  
  RESULTS
  In protic media, the NPD derivative gave a reversible well-defined peak either on Hg or glassy carbon electrodes in a reaction involving two electrons and two protons to give the hydroxylamine derivative. In mixed aqueous-organic media (pH 9) and in aprotic media, nitroso radical anion was isolated and characterized, exhibiting second-order dimerization rate constant (k2) values of 11,300 +/- 210 [Ms](-1) and 8,820 +/- 78 [Ms](-1), respectively. Reactivity of the nitroso radical anion with relevant pharmacologic targets revealed a significant interaction with the tested endo/xenobiotics (cysteamine, GSH, N-acetylcysteine, and adenine).
  
  
  CONCLUSIONS
  Both in mixed and aprotic media, NPD generated free-radical species, the nitroso radical anion. Taking into account their respective interaction rate constants, the following tentative rank order of reactivity can be established as follows: cysteamine > N-acetylcysteine > GSH > adenine.
authors.affiliation: Laboratory of Bioelectrochemistry, Faculty of Chemical & Pharmaceutical Sciences, University of Chile, Santiago. lnunezv@ciq.uchile.cl
authors.forename: L J
authors.initials: LJ
authors.lastname: Núñez-Vergara
authors.forename: S
authors.initials: S
authors.lastname: Bollo
authors.forename: J
authors.initials: J
authors.lastname: Fuentealba
authors.forename: J C
authors.initials: JC
authors.lastname: Sturm
authors.forename: J A
authors.initials: JA
authors.lastname: Squella
mesh_terms: D004563:Electrochemistry; D004572:Electrolysis / Q000379:methods; D009543:Nifedipine / Q000737:chemistry* / Q000378:metabolism; D009603:Nitroso Compounds / Q000737:chemistry* / Q000378:metabolism; D011725:Pyridines / Q000737:chemistry* / Q000378:metabolism
chemical_list: D009603:Nitroso Compounds; D011725:Pyridines; D009543:Nifedipine