Dehydrogenation of Phenols. II. Dehydrogenation Polymers from Guaiacol.

Lindgren, B.; Norman, Nico; Åselius, J.; Refn, Susanne; Westin, Gertrud

doi:10.3891/acta.chem.scand.14-2089

Cited by 18 publications

(10 citation statements)

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“…These results provide evidence that the oxidation of NADPH does not involve a free nucleotide radical intermediate, but that this is probably due to a direct electron-transfer reaction between NADPH and a two-electron-oxidized guaiacol intermediate. the normal peroxidation cycle, the characteristic red-brown species developed from the oxidation of guaiacol by peroxidase was ascribed to guaiacol dimers with quinone residues [11], thus supporting the hypothetical rapid dimerization step involving cross-linking of phenoxyl radicals [12,13]. These results apparently contradicted the idea prevalent that tetraguaiacol formation was being monitored at 470 nm [14].…”

Section: Introductionmentioning

confidence: 73%

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Oxidation of guaiacol by myeloperoxidase: a two-electron-oxidized guaiacol transient species as a mediator of NADPH oxidation

Capeillère‐Blandin

1998

Biochemical Journal

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The present study was first aimed at a complete steady-state kinetic analysis of the reaction between guaiacol (2-methoxyphenol) and the myeloperoxidase (MPO)/H2O2 system, including a description of the isolation and purification of MPO from human polymorphonuclear neutrophil cells. Secondly, the overall reaction of the oxidation of NADPH, mediated by the reactive intermediates formed from the oxidation of guaiacol in the MPO/H2O2 system, was analysed kinetically. The presence of guaiacol stimulates the oxidation of NADPH by the MPO/H2O2 system in a concentration-dependent manner. Concomitantly, the accumulation of biphenoquinone (BQ), the final steady-state product of guaiacol oxidation, is lowered, and even inhibited completely, at high concentrations of NADPH. Under these conditions, the stoichiometry of NADPH:H2O2 is 1, and the oxidation rate of NADPH approximates to that of the rate of guaiacol oxidation by MPO. The effects of the presence of superoxide dismutase, catalase and of anaerobic conditions on the overall oxidation of NADPH have also been examined, and the data indicated that superoxide formation did not occur. The final product of NADPH oxidation was shown to be enzymically active NADP+, while guaiacol was generated continuously from the reaction between NADPH and oxidized guaiacol product. In contrast, similar experiments performed on the indirect, tyrosine-mediated oxidation of NADPH by MPO showed that a propagation of the free radical chain was occurring, with generation of both O2(-.) and H2O2. BQ, in itself, was able to spontaneously oxidize NADPH, but neither the rate nor the stoichiometry of the reaction could account for the NADPH-oxidation process involved in the steady-state peroxidation cycle. These results provide evidence that the oxidation of NADPH does not involve a free nucleotide radical intermediate, but that this is probably due to a direct electron-transfer reaction between NADPH and a two-electron-oxidized guaiacol intermediate.

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Section: Introductionmentioning

confidence: 73%

“…(4)]. The biphenol was subsequently found to undergo further oxidation to biphenoquinone (BQ) more readily than guaiacol [11]. A two-electron oxidation mechanism could be feasible if the phenoxyl radicals, G-Od, are deactivated by dismutation, leading to a phenoxyl cation [G-O + ; eqn.…”

Section: Introductionmentioning

confidence: 99%

Oxidation of guaiacol by myeloperoxidase: a two-electron-oxidized guaiacol transient species as a mediator of NADPH oxidation

Capeillère‐Blandin

1998

Biochemical Journal

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“…The 366 molecular ion was prominent, however, in an EI mass spectrum of a freeze dried HPLC isolate of (F). 4,4'-Diphenoquinones are apparently also present as structural units in guaiacol polymers obtained by enzymic oxidation processes, but these materials including 'tetraguaiacoquinone' have never been adequately characterized (Lindgren 1960;Crawford et al 1981).…”

Section: Resultsmentioning

confidence: 99%

The reaction of guaiacol with iron III and chromium VI compounds as a model for wood surface modification

1995

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Summary The reaction of ferric chloride with the lignin model guaiacol affords primarily a complex mixture of coupled guaiacol oligomers. Major components were the symmetrical carbon-carbon coupled dimer 3,Y-dimethoxy-[1,1'-biphenyl]-4,4'-diol and the trimer 3,Y',5'-trimethoxy-[1,1':Y, l"-terphenyl]-4,4',4"-triol which were isolated by preparative HPLC and characterized by 1HNMR spectroscopy and mass spectrometry. An unstable component believed to be a 4,4'-diphenoquinone derived from the trimer was also prominent. The reaction of chromium trioxide with guaiacol yields the same dimer, trimer and diphenoquinone as well as 2-methoxy-p-benzoquinone. The major product with chromium trioxide, however, is an inert, highly insoluble polymer which was shown by degradation to contain guaiacol oligomers bound or crosslinked by hydroxylated chromium species. Magnetic susceptibility measurements clearly indicated that the valency of chromium in the polymer was + 3. It is postulated that similar complexes formed from phenolic lignin units are responsible for the weather resistance of chromium trioxide treated wood surfaces. In a broader context this study is relevant to the fixation of hexavalent chromium from a range of widely used wood preservative formulations.

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“…When the HRP-HzO2 system acts on different aromatic phenols, dimeric and tetrameric oxidation products are formed (Lindgren 1960;Whitaker 1972;Makinen and Tenovuo 1982).…”

Section: Product@) Obtained When 245-thbp Is Oxidized By the Hrp-hzmentioning

confidence: 99%

“…Peroxidase can carry out four different types of reactions: peroxidatic oxidation, oxidatic, catalatic and hydroxylation (Whitaker 1972). The peroxidatic oxidation reaction occurs in the presence of H202 with a variety of compounds that can serve as substrates (AH,) yielding dimeric and tetrameric oxidation products (Lindgren 1960;Herzog and Fahimi 1973;Josephy et al 1982;Makinen and Tenovuo 1982;Whitaker 1972). The catalatic reaction occurs between two molecules of H202, while the oxidatic and hydroxylation reactions occur with different substrates (AH,) in the absence of H202 but require oxygen instead.…”

Section: Introductionmentioning

confidence: 99%

2,4,5-Trihydroxybutyrophenone (2,4,5-Thbp) as a Substrate for Horseradish Peroxidase

Kahn

Zakin

1996

J Food Biochemistry

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2,4,5‐trihydroxybutyrophenone (2,4,5‐THBP), in the presence of hydrogen peroxide (H2O2), is a substrate for horseradish peroxidase (HRP) with a Km value of 2.5 mM. An intermediate red product(s), probably 2,4,5‐THBP quinone, characterized by a peak at 490–500 nm, was detected and the time course of its conversion to the final red product(s) was studied. The relationships between the rate of 2,4,5‐THBP oxidation to pigmented product(s) as a function of various concentrations of H2O2, 2,4,5‐THBP and HPR are described.

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Dehydrogenation of Phenols. II. Dehydrogenation Polymers from Guaiacol.

Cited by 18 publications

References 0 publications

Oxidation of guaiacol by myeloperoxidase: a two-electron-oxidized guaiacol transient species as a mediator of NADPH oxidation

Oxidation of guaiacol by myeloperoxidase: a two-electron-oxidized guaiacol transient species as a mediator of NADPH oxidation

The reaction of guaiacol with iron III and chromium VI compounds as a model for wood surface modification

2,4,5-Trihydroxybutyrophenone (2,4,5-Thbp) as a Substrate for Horseradish Peroxidase

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