- Imidazolium-Based Ionic Liquids as Efficient Reagents for the C?O Bond Cleavage of Lignin
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The demethylation of lignin in ionic liquids (ILs) was investigated by using pure lignin model monomers and dimers together with dioxane-isolated lignins from poplar, miscanthus, and maize. Different methylimidazolium ILs were compared and the samples were treated with two different heating processes: microwave irradiation and conventional heating in a sealed tube. The conversion yield and influence of the treatment on the lignin structure were assessed by 31P NMR spectroscopy, size-exclusion chromatography, and thioacidolysis. The acidic methylimidazolium IL [HMIM]Br was shown to be an effective combination of solvent and reagent for the demethylation and depolymerization of lignin. The relatively mild reaction conditions, the clean work-up, and the ability to reuse the IL makes the described procedure an attractive and new green method for the conversion of lignin to produce phenol-rich lignin oligomers.
- Thierry, Marina,Majira, Amel,Pégot, Bruce,Cezard, Laurent,Bourdreux, Flavien,Clément, Gilles,Perreau, Fran?ois,Boutet-Mercey, Stéphanie,Diter, Patrick,Vo-Thanh, Giang,Lapierre, Catherine,Ducrot, Paul-Henri,Magnier, Emmanuel,Baumberger, Stéphanie,Cottyn, Betty
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p. 439 - 448
(2018/02/06)
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- Interference of carbidopa and other catechols with reactions catalyzed by peroxidases
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Background: A number of compounds, including ascorbic acid, catecholamines, flavonoids, p-diphenols and hydrazine derivatives have been reported to interfere with peroxidase-based medical diagnostic tests (Trinder reaction) but the mechanisms of these effects have not been fully elucidated. Methods: Reactions of bovine myeloperoxidase with o-dianisidine, bovine lactoperoxidase with ABTS and horseradish peroxidase with 4-aminoantipyrine/phenol in the presence of carbidopa, an anti-Parkinsonian drug, and other catechols, including L-dopa, were monitored spectrophotometrically and by measuring hydrogen peroxide consumption. Results: Chromophore formation in all three enzyme/substrate systems was blocked in the presence of carbidopa and other catechols. However, the rates of hydrogen peroxide consumption were not much affected. Irreversible enzyme inhibition was also insignificant. Conclusions: Tested compounds reduced the oxidation products or intermediates of model substrates thus preventing chromophore formation. This interference may affect interpretation of results of diagnostic tests in samples from patients with Parkinson's disease treated with carbidopa and L-dopa. General significance: This mechanism allows prediction of interference in peroxidase-based diagnostic tests for other compounds, including drugs and natural products.
- G?sowska-Bajger, Beata,Nishigaya, Yuki,Hirsz-Wiktorzak, Krystyna,Rybczyńska, Anna,Yamazaki, Toshimasa,Wojtasek, Hubert
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p. 1626 - 1634
(2018/04/26)
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- The synthesis of 1-(3,4-dihydroxyphenyl)-2-propanone and 1-(3,4-dihydroxyphenyl)-2-propanol
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Acetylation of 1,3-propylenedithioacetal of 3,4-dihydroxybenzaldehyde silyl ether 5 followed by reductive desulfurization of the masking group gave ketone 7 which was reduced to alcohol 8. Hydrolysis of the silyl protecting groups in 7 and 8 afforded the title compounds which were metabolites of 1-(4-hydroxy-3-methoxyphenyl)-2-propanone, found in smoked meat.
- Brozda
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p. 573 - 575
(2007/10/02)
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- Further studies on the metabolism of carbidopa, (-) L α hydrazino 3,4 dihydroxy α methylbenzenepropanoic acid monohydrate, in the human, rhesus monkey, dog, and rat
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Major urinary metabolites of carbidopa were identified. Estimates were made based on the recovery of radioactivity or by GLC analysis of pooled urine of the amounts of the urinary metabolites II (2 methyl 3' methoxy 4' hydroxy phenyl propionic acid), III
- Vickers,Stuart,Hucker,VandenHeuvel
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p. 134 - 138
(2007/10/12)
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