Photolyse et photo-oxydation des diphénols en solution aqueuse diluée

Perbet, Gilles; Filiol, Christian; Boule, Pierre; Lemaire, Jácques

doi:10.1051/jcp/1979760089

Cited by 13 publications

(3 citation statements)

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“…A similar phenomenon can be observed in the production of phenoxy radicals from simple phenols like phenol (Audureau et al, 1976;Grabner and Getoff, 1982;Mialocq et al, 1980). diphenols (Perbet et al, 1979), and orthophenylphenol (Coulangeon et al, 1980) in aqueous oxygenated solution. In the work of Kalyanaraman et al (1984), photoionization and photohomolysis of the 0-H bond are presented as competitive pathways of the melanin photolysis.…”

Section: Rsupporting

confidence: 63%

Electron Spin Resonance of Eumelanin From Hair: Photoinduced Radicals in Solid Matrix

Bibang

Arnaud

Lemaire

et al. 1989

Pigment Cell Research

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KBr matrices appear to be convenient media to reveal the radicals formed on light exposure of eumelanin dispersions. The ESR signal of eumelanin dispersed at low concentration in KBr pellets is analyzed during and after irradiation at various wavelengths. Different types of radicals are observed. R'1- and R1-types of radicals are assigned, respectively, to neutral and deprotonated intrinsic phenoxy radicals of eumelanin. R'1 can be oxidized by oxygen as opposite to R1. R2- and R'2-types are formed in the indolic site. Water favours the conversion of R2, unreactive with oxygen, into R'2 which can be oxidized. R'1 and R2 result of an electron photoejection, respectively, from the phenolic and the indolic site. The R3-type radicals are associated with the band-to-band excitation of eumelanin considered as a semiorganized solid.

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Section: Rsupporting

confidence: 63%

Electron Spin Resonance of Eumelanin From Hair: Photoinduced Radicals in Solid Matrix

Bibang

Arnaud

Lemaire

et al. 1989

Pigment Cell Research

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“…When the sample of fenoterol was deaerated by bubbling N 2 gas through the solution, the rate of the reaction and the extent of oxidation both decreased by approximately 50% (not shown), suggesting that oxygen is involved, at least partially, in the oxidative transformation of the agonist. One possible explanation of this effect may be that oxygen adds to phenoxyl radicals resulting in hydroxylation of the aromatic ring, a process known to occur during aerobic (photo)oxidation of resorcinols (29). …”

Section: Resultsmentioning

confidence: 99%

“…However, if formed, such a molecule would be highly electrophilic and after hydrolysis might produce 2-hydroxy-1,4-benzoquinone type chromophore, for which intramolecular cyclization would be possible. Formation of 2-hydroxy-1,4-benzoquinone from resorcinol has been reported to occur through enzymatic conversion (52,53) and reaction of the resorcinol semiquinone with oxygen (29). The observation that the rate and the extent of oxidation of fenoterol depend on oxygen (they both decrease in deaerated solutions) partially supports the latter mechanism.…”

Section: Discussionmentioning

confidence: 99%

Peroxidative Metabolism of β₂-Agonists Salbutamol and Fenoterol and Their Analogues

Reszka¹,

McGraw

Britigan

2009

Chem. Res. Toxicol.

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Phenolic β 2 -adrenoreceptor agonists salbutamol, fenoterol and terbutaline relax smooth muscle cells that relieve acute airway bronchospasm associated with asthma. Why their use sometimes fails to relieve bronchospasm, and why the drugs appear to be less effective in patients with severe asthma exacerbations, remains unclear. We show that in the presence of hydrogen peroxide, both myeloperoxidase, secreted by activated neutrophils present in inflamed airways, and lactoperoxidase, which is naturally present in the respiratory system, catalyze oxidation of these β 2 -agonists. Azide, cyanide, thiocyanate, ascorbate, glutathione, and methimazole inhibited this process, while methionine was without effect. Inhibition by ascorbate and glutathione was associated with their oxidation to corresponding radical species by the agonists'-derived phenoxyl radicals. Using electron paramagnetic resonance (EPR), we detected free radical metabolites from β 2 -agonists by spin trapping with 2-methyl-2-nitrosopropane (MNP). Formation of these radicals was inhibited by pharmacologically-relevant concentrations of methimazole and dapsone. In alkaline buffers radicals from fenoterol and its structural analog, metaproteronol, were detected by direct EPR. Analysis of these spectra suggests that oxidation of fenoterol and metaproterenol, but not terbutaline, causes their transformation through intramolecular cyclization by addition of their amino nitrogen to the aromatic ring. Together, these results indicate that phenolic β 2 -agonists function as substrates for airway peroxidases and that the resulting products differ in their structural and functional properties from their parent compounds. They also suggest that these transformations can be modulated by pharmacological approaches using appropriate peroxidase inhibitors or alternative substrates. These processes may affect therapeutic efficacy and also play a role in adverse reactions of the β 2 -agonists.

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Mechanism of Phototransformation of Phenol and Derivatives in Aqueous Solution

Richard¹,

Grabner

1999

The Handbook of Environmental Chemistry

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Photolyse et photo-oxydation des diphénols en solution aqueuse diluée

Cited by 13 publications

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Electron Spin Resonance of Eumelanin From Hair: Photoinduced Radicals in Solid Matrix

Electron Spin Resonance of Eumelanin From Hair: Photoinduced Radicals in Solid Matrix

Peroxidative Metabolism of β₂-Agonists Salbutamol and Fenoterol and Their Analogues

Mechanism of Phototransformation of Phenol and Derivatives in Aqueous Solution

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Photolyse et photo-oxydation des diphénols en solution aqueuse diluée

Cited by 13 publications

References 0 publications

Electron Spin Resonance of Eumelanin From Hair: Photoinduced Radicals in Solid Matrix

Electron Spin Resonance of Eumelanin From Hair: Photoinduced Radicals in Solid Matrix

Peroxidative Metabolism of β2-Agonists Salbutamol and Fenoterol and Their Analogues

Mechanism of Phototransformation of Phenol and Derivatives in Aqueous Solution

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Peroxidative Metabolism of β₂-Agonists Salbutamol and Fenoterol and Their Analogues