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Catechol Derivatives (catechol + derivative)
Selected AbstractsInvestigation of the larvicidal activity of Pothomorphe peltata and isolation of the active constituentPHYTOTHERAPY RESEARCH, Issue S1 2002Dr E. Mongelli Abstract The insecticidal activity of the leaves of Pothomorphe peltata (Piperaceae) was evaluated on Aedes aegypti larvae. The active methanol extract was subjected to a bioactivity-directed fractionation, monitored by the larvicidal assay, and led to the isolation of a catechol derivative, 4-nerolidylcatechol. This compound was quite potent against Aedes aegypti larvae (LC50,=,9.1,µg/mL). Copyright © 2002 John Wiley & Sons, Ltd. [source] Enzymatic Synthesis of 3,-Hydroxyacetaminophen Catalyzed by TyrosinaseBIOTECHNOLOGY PROGRESS, Issue 6 2003Edelmira Valero 3,-Hydroxyacetaminophen, a catechol metabolite of N -acetyl- p -aminophenol (acetaminophen) and N -acetyl- m -aminophenol (a structural analogue of acetaminophen and considered as a possible alternative because it is not hepatotoxic), is enzymatically synthesized for the first time using mushroom tyrosinase. Although reported to be weakly hepatotoxic in vivo, this catechol derivative of acetaminophen is not commercially available. This compound was obtained from its monophenolic precursor, acetaminophen, using the enzyme tyrosinase in the presence of an excess of ascorbic acid, thus reducing back the o -quinone product of catalytic activity to the catechol acetaminophen derivative. A mathematical model of the system is proposed, which is also applicable to the tyrosinase-mediated synthesis of any o -diphenolic compound from its corresponding monophenol. This synthesis procedure is continuous, easy to perform and control, and adaptable to a bioreactor with the immobilized enzyme for industrial purposes in a nonpolluting way. [source] Natural polyphenols as chain-breaking antioxidants during methyl linoleate peroxidationEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 8 2010Ivan Tichonov Abstract A technique based on monitoring oxygen consumption was applied to study 11 natural and model polyphenols (PP, QH2) as well as four typical monophenolics as a chain-breaking antioxidant during the controlled chain oxidation of methyl linoleate (ML) in bulk at 37°C. The antioxidant activities of QH2 were characterized by two parameters: the rate constant k1 for reaction of QH2 with the peroxy radical : (i) QH2,+,,,,,+,LOOH and the stoichiometric factor of inhibition, f, which shows how many kinetic chains may be terminated by one molecule of QH2. The rate constant k1 were reduced significantly by factor of 4 ,28 as compared to these determined during the oxidation of styrene in bulk; the effect was typically more pronounced for catechol derivatives than for pyrogallol derivatives. At the same time, f for QH2 was found to be close to two independent of the number of active OH groups, similar to that determined earlier during the inhibited oxidation of styrene. The formation of H bond between OH group of QH2 and carboxyl group of ML is suggested as a reason for reducing effect of ML on k1. Practical applications: This work reports rate constants for the reaction of lipid peroxyl radical with phenolics and stoichiometric coefficient of inhibition, which characterize the antioxidant activity (AOA) of 15 natural and model PP, QH2 during the controlled peroxidation of ML. The reactivity of PP, QH2 during the oxidation of ML is routinely lower than the reactivity during the oxidation of non-polar model hydrocarbons. This information may be useful to estimate the AOA of natural PP, QH2 in real systems of practical significance including plant oils, fats, food-stuffs, biological objects, and similar. [source] Estimation of homogeneous rate constants of reaction of electrochemically generated ortho -benzoquinones with 1,3-indandioneINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 11 2007Davood Nematollahi Electrochemical oxidation of some catechol derivatives has been studied in the presence of 1,3-indandione as nucleophile in aqueous solution, by means of cyclic voltammetry and controlled-potential coulometry. The results indicate the participation of electrochemically produced o -benzoquinones in the Michael reaction with 1,3-indandione to form the corresponding new catechol derivatives. On the basis of the EC mechanism, the observed homogeneous rate constants (kobs) of reaction of produced o -benzoquinones with 3-indandione were estimated by comparing the experimental cyclic voltammograms with the digitally simulated results. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 605,613, 2007 [source] Kinetic study of electrochemically induced Michael reactions of o -benzoquinones with 2-acetylcyclohexanone and 2-acetylcyclopentanoneJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 1 2007Davood Nematollahi Abstract The reaction of electrochemically generated o -benzoquinones (2a-f) as Michael acceptors with 2-acetylcyclohexanone (ACH) and 2-acetylcyclopentanone (ACP), as nucleophiles has been studied in various pHs using cyclic voltammetry. The results indicate that the participation of o -benzoquinones (2a-f) in the Michael reaction with acetylcyclohexanone (ACH) to form the corresponding catechol derivatives (4a-f). Based on an EC mechanism, the homogeneous rate constants were estimated by comparing the experimental cyclic voltammetric responses with the digital simulated results. Copyright © 2007 John Wiley & Sons, Ltd. [source] Development of New and Selective Trypanosoma cruzi trans-Sialidase Inhibitors from Sulfonamide Chalcones and Their DerivativesCHEMBIOCHEM, Issue 15 2009Jin Hyo Kim Abstract A series of sulfonamide-containing hydroxylated chalcone (4,7) and quinolinone (8, 9) derivatives was synthesised and tested for inhibition of the trans-sialidase from Trypanosoma cruzi (TcTS). IC50 values for these inhibitors ranged from 0.6 to 7.3 ,M, with the dihydroxylated (catechol) derivatives being the tightest binders. Full kinetic analyses of inhibition were performed for these catechol derivatives, both for the transglycosylation reaction in the presence of lactose and for the hydrolysis reaction in its absence. Competitive inhibition was seen in each case with Ki values for 5, 7 and 9 of 2.0, 2.2 and 0.2 ,M, respectively, in the absence of lactose, and 4.6, 3.7 and 0.4 ,M in its presence. None of the compounds tested showed any significant inhibition of the human sialidase Neu2, at concentrations up to 200 ,M. [source] | |||||||||||||