Mechanism of oxidation of 1-benzyl-1,4-dihydronicotinamide by the biologically active p-benzoquinone derivative, avarone, in a cationic micellar medium

Davidović, Asima; Tabaković, Ibro; Sladić, Dušan; Dogović, Nikola; Gašić, Miroslav J.

doi:10.1016/0302-4598(91)85007-o

Cited by 8 publications

(1 citation statement)

References 24 publications

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“…28 In fact, comparison of the electrochemical reduction of avarone in the presence of CTAB micelles with the same process in a homogeneous waterethanol mixture shows an anodic shift of the quinone oneelectron reduction potential in the presence of CTAB which evidences the role of CTAB positive charge in stabilizing the avarone semiquinone and, thus increasing the quinone redox potential. 29 Since ascorbate is a negatively charged reducing agent and, thus, it is attracted to the DMPC/CTAB interface, we also used DTT as the reducing agent. The pK a value of this reducing agent is 10.1, 30 i.e.…”

Section: Resultsmentioning

confidence: 99%

Role of membrane charge and semiquinone structure on oxygen consumption rates

Alegrı́a

Rivera

Cordones

et al. 2002

J. Chem. Soc., Perkin Trans. 2

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Rates of oxygen consumption of air-saturated aqueous solutions containing either 2,3-dimethoxy-5-methylbenzoquinone (UQ-0), 1,4-naphthoquinone (NQ) or phenanthroquinone (PHQ) and ascorbate were measured in the presence or absence of large unilamellar vesicles (LUVs) composed of either dimyristoylphosphatidylcholine (DMPC) or equimolar mixtures of DMPC with dimyristoylphospahtidic acid (DMPA) or hexadecyltrimethylammonium bromide (CTAB), at physiological pH. Semiquinone hydrophobicities follow the same order as that of the corresponding quinones. Rates increase with positively charged LUV concentration and decrease with either neutral or negatively charged LUV concentration in samples containing the hydrophobic quinones NQ and PHQ. Rates remain essentially unchanged in the presence of the most hydrophilic quinone, UQ-0. An increase in the ionic strength of the solution partially inhibits the observed changes in the rate of oxygen consumption, R ox , caused by the presence of positively charged membranes, thus implying that such changes are of electrostatic nature. Similar trends with membrane charge are observed for the rates of oxygen consumption in the presence of PHQ and dithiothreitol. The observed increase in the ascorbate oxidation rate in the presence of positively charged lipids occurs in systems where a decrease in semiquinone disproportionation is also detected, thus, implying that an increase in the quinone one-electron redox potential, caused by semiquinone-positively-charged-membrane interaction, could contribute to the observed effects.

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Section: Resultsmentioning

confidence: 99%

Role of membrane charge and semiquinone structure on oxygen consumption rates

Alegrı́a

Rivera

Cordones

et al. 2002

J. Chem. Soc., Perkin Trans. 2

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Electrooxidation of 2-Mercaptopyridine-N-oxide (Pyrithione) at Carbon Electrodes versus Mercury Electrodes

1998

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The electrooxidation of the bactericide and fungicide agent 2-mercaptopyridine-N-oxide (PySH), or pyrithione, was investigated by using mercury (Hg), glassy carbon (GCE), plastic formed carbon (PFCE) and paste (CPE) electrodes. From controlled-potential electrolyses or chronoamperometric measurements, the number of electrons involved in the oxidation processes was found to be close to unity in all cases. Voltammetric measurements showed that the irreversibility of the electron transfer must be related to the roughness and ordering in the surface of the electrode material: as the amorphous character of the carbon electrode was increased, the transfer appeared faster. Other effects as the O/C ratio or the removal of impurities can also influence the reversibility of the transfer. The rate constants of the electron transfers at zero potential were obtained. In addition, the extension of the adsorptive oxidation decreased when the amorphous character of the electrode was increased, but the Gibbs free enthalpy of this process did not vary from one electrode to another nor for the Hg electrode.

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Electroreduction of some pyridine carboxamides on carbon electrodes in aqueous solutions

et al. 1997

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The electroreductions of the NAD' model compounds nicotinamide (I), N,-methyl nicotinamide (11), "-methyl nicotinamide (111) and isonicotinamide (IV) on carbon electrodes have been studied in aqueous media in the pH range 0-12 by linear-sweep cyclic voltammetry (Scheme 1, I-IV). Logarithmic analyses of the reduction peaks were performed by computing the convolution of the current with time as a function of the potential. On the basis of the experimental results it was concluded that the irreversibility of the electron transfers increased when a glassy carbon electrode was used, and this irreversibility being more marked when a plastic formed carbon electrode was employed. The reduction processes occurred with more difficulty on carbon electrodes than on mercury electrodes. Both the reduction and the reoxidation (when occurred) processes changed with respect to those observed on mercury electrodes, being irreversible electron transfers the rate-determining steps in most cases. Thus, for compounds I, I1 and 111 at pH < 2 the reductions occurred by the uptake of two electrons and two H+ ions, and the rate determining step was found to be the first one-electron transfer, for I and 111, and the irreversible second electron transfer, preceded by the uptake of an I%+ ion, for 11. At pH > 3 the processes consisted of electrodimerization reactions, preceded by the protonation of the heterocyclic nitrogen in cases I and IU. The second electron transfer of the electroreduction of IV always appeared irreversible, in contrast with that found for mercury electrodes.

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Mechanism of oxidation of 1-benzyl-1,4-dihydronicotinamide by the biologically active p-benzoquinone derivative, avarone, in a cationic micellar medium

Cited by 8 publications

References 24 publications

Role of membrane charge and semiquinone structure on oxygen consumption rates

Role of membrane charge and semiquinone structure on oxygen consumption rates

Electrooxidation of 2-Mercaptopyridine-N-oxide (Pyrithione) at Carbon Electrodes versus Mercury Electrodes

Electroreduction of some pyridine carboxamides on carbon electrodes in aqueous solutions

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