Mechanism of catalytic ascorbic acid oxidation system Cu<sup>2+</sup>–ascorbic acid–O<sub>2</sub>

Штамм, Е. В.; Purmal, A. P.; Skurlatov, Yu. I.

doi:10.1002/kin.550110503

Cited by 53 publications

(33 citation statements)

References 47 publications

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“…This may explain the decreased overall reaction rate at the higher acetonitrile concentration (Figure 7). The slight increase in the reaction rate at low acetonitrile concentration was also observed by Shtamm et al [33] for copper(II) catalyzed oxidation of ascorbic acid. They suggested that the increase of the overall rate at low acetonitrile concentration was an effect of acetonitrile on the rate of copper(I) initiation reaction via the formation of the transition complex [Cu(II)CH 3 CNascorbate].…”

Section: Effect Of Solventsupporting

confidence: 59%

Catecholase biomimetic catalytic activity of copper(II) complexes with 2-methyl-3-amino-(3H)-quinazolin-4-one

EI-Mehasseb

Ramadan

Issa

2006

Transition Met Chem

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The oxidation of catechol by molecular oxygen in the presence of a catalytic amount of copper(II) complex with 2-methyl-3-amino-(3H)quinazoline-4-one (MAQ) and various anions (Cl ) , Br ) , ClO 4 ) , SCN ) , NO 3 ) and SO 4 -) was studied. The catecholase biomimetic catalytic activity of the copper(II) complexes has been determined spectrophotometrically by monitoring the oxidative transformation of catechol to the corresponding light absorbing o-quinone (Q). The rate of the catalytic oxidation reaction was investigated and correlated with the catalyst structure, time, concentration of catalyst and substrate and finally solvent effects. Addition of pyridine or Et 3 N showed a dramatic effect on the rate of oxidation reaction. Kinetic investigations demonstrate that the rate of oxidation reaction has a first order dependence with respect to the catalyst and catechol concentration and obeying Michaelis-Menten Kinetics. It was shown that the catalytic activity depends on the coordination environment of the catalyst created by the nature of counter anions bound to copper(II) ion in the complex molecule and follows the order:To further elucidate the catalytic activity of the complexes, their electrochemical properties were investigated and the catecholase mimetic activity has been correlated with the redox potential of the Cu 2+ /Cu + couple in the complexes.

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Section: Effect Of Solventsupporting

confidence: 59%

Catecholase biomimetic catalytic activity of copper(II) complexes with 2-methyl-3-amino-(3H)-quinazolin-4-one

EI-Mehasseb

Ramadan

Issa

2006

Transition Met Chem

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“…A 2.5-to 3-fold increase in HR generation was caused by the addition of 100 mM NaCl, whereas 250 mM NaCl triggered a 4-to 4.5-fold increase compared to the basal level of HR generation ( Fig. 6B,F (Shtamm et al, 1977). Because some O 2 is always dissolved in water, we used deoxygenated water; all solutions were sealed with parafilm (Halliwell and Gutteridge, 1999).…”

Section: Salt-induced Generation Of Hrs In Intact Rootsmentioning

confidence: 99%

Arabidopsis root K+-efflux conductance activated by hydroxyl radicals: single-channel properties, genetic basis and involvement in stress-induced cell death

Demidchik

Cuin

Svistunenko

et al. 2010

Journal of Cell Science

456

369

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SummaryReactive oxygen species (ROS) are central to plant stress response, signalling, development and a multitude of other processes. In this study, the plasma-membrane hydroxyl radical (HR)-activated K + channel responsible for K + efflux from root cells during stress accompanied by ROS generation is characterised. The channel showed 16-pS unitary conductance and was sensitive to Ca 2+ , tetraethylammonium, Ba 2+ , Cs + and free-radical scavengers. The channel was not found in the gork1-1 mutant, which lacks a major plasma-membrane outwardly rectifying K + channel. In intact Arabidopsis roots, both HRs and stress induced a dramatic K + efflux that was much smaller in gork1-1 plants. Tests with electron paramagnetic resonance spectroscopy showed that NaCl can stimulate HR generation in roots and this might lead to K + -channel activation. In animals, activation of K + -efflux channels by HRs can trigger programmed cell death (PCD). PCD symptoms in Arabidopsis roots developed much more slowly in gork1-1 and wild-type plants treated with K + -channel blockers or HR scavengers. Therefore, similar to animal counterparts, plant HR-activated K + channels are also involved in PCD. Overall, this study provides new insight into the regulation of plant cation transport by ROS and demonstrates possible physiological properties of plant HR-activated K + channels.

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“…Under such conditions, trapping agents or superoxide dismutase may easily fail to show a significant effect, especially as the above-mentioned radicals would act as simple intermediates and not as essential chain carriers. [18], and deviation of experimental curves in that direction has been observed in the present work, notably at low pH ( < 2.5) and at low [MeCN] ( < 0 . 7~) .…”

mentioning

confidence: 47%

Cuprous Complexes and Dioxygen. Part 12.. Rate law and mechanism of the copper‐catalyzed oxidation of ascorbic acid in aqueous acetonitrile

Li¹,

Zuberbühler²

1992

Helvetica Chimica Acta

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The copper-catalyzed oxidation of ascorbic acid (AscH,) has been studied with a Clurk electrode in aqueous MeCN. Cu' or CU" may be equally used as the source of metal ion, without influence on the rate law. At sufficiently high [MeCN], the rate of the overall reaction is essentially given by the rate of Cu' autoxidation: the reaction is of first order with respect to [Cuk:'] [13-151. If Cu' is supposed to be essential in catalytic ascorbate oxidation, the very easy autoxidation of Cu& [l] [18] [24-261 should be taken into account, and any proposed mechanism should be compatible with the rate law of that latter reaction. With the exception of some preliminary results for media containing high amounts of C1-, this does not seem to be the case in general [2] [3]. It is the aim of the present work to firmly establish the role of Cu' autoxidation in the Cu oxidation of ascorbate and to show the full compatibility of the corresponding rate laws in aqueous MeCN. In addition, we hope to have laid a basis for a consistent mechanism of this reaction in the absence of MeCN or other Cu'-stabilizing ligands such as chloride and ally1 alcohol, too.

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Mechanism of catalytic ascorbic acid oxidation system Cu²⁺–ascorbic acid–O₂

Cited by 53 publications

References 47 publications

Catecholase biomimetic catalytic activity of copper(II) complexes with 2-methyl-3-amino-(3H)-quinazolin-4-one

Catecholase biomimetic catalytic activity of copper(II) complexes with 2-methyl-3-amino-(3H)-quinazolin-4-one

Arabidopsis root K+-efflux conductance activated by hydroxyl radicals: single-channel properties, genetic basis and involvement in stress-induced cell death

Cuprous Complexes and Dioxygen. Part 12.. Rate law and mechanism of the copper‐catalyzed oxidation of ascorbic acid in aqueous acetonitrile

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Mechanism of catalytic ascorbic acid oxidation system Cu2+–ascorbic acid–O2

Cited by 53 publications

References 47 publications

Catecholase biomimetic catalytic activity of copper(II) complexes with 2-methyl-3-amino-(3H)-quinazolin-4-one

Catecholase biomimetic catalytic activity of copper(II) complexes with 2-methyl-3-amino-(3H)-quinazolin-4-one

Arabidopsis root K+-efflux conductance activated by hydroxyl radicals: single-channel properties, genetic basis and involvement in stress-induced cell death

Cuprous Complexes and Dioxygen. Part 12.. Rate law and mechanism of the copper‐catalyzed oxidation of ascorbic acid in aqueous acetonitrile

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Mechanism of catalytic ascorbic acid oxidation system Cu²⁺–ascorbic acid–O₂