The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Jeroni Morey - One of the best experts on this subject based on the ideXlab platform.
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solid state redox chemistry of Hydroquinones and quinones
Tetrahedron, 1993Co-Authors: Jeroni MoreyAbstract:Abstract Solid state ceric ammonium nitrate (CAN) oxidation of Hydroquinones to the corresponding quinones, gives best results when operating with ultrasonic irradiation. Nitrogen dioxide plays a key role in these “solid-solid” oxidations. The oxidation of Hydroquinones to quinones can also be achieved in a unique “solid-solid-solid” reaction, i.e., by using a limited amount of CAN in the presence of a full equivalent of a solid cooxidant such as KBrO3. Reduction of quinones with sodium dithionite in the solid state gives rise to the corresponding highly colored quinhydrones and, eventually, to Hydroquinones.
Albena T Dinkovakostova - One of the best experts on this subject based on the ideXlab platform.
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activation of the nrf2 signaling pathway by copper mediated redox cycling of para and ortho Hydroquinones
Chemistry & Biology, 2010Co-Authors: Xiu Jun Wang, John D Hayes, Larry G Higgins, Roland C Wolf, Albena T DinkovakostovaAbstract:Summary Transcription factor NF-E2 p45-related factor 2 (Nrf2) mediates adaptation to oxidants and electrophiles through up-regulating genes that contain antioxidant response elements (AREs) in their promoters. Using the stably transfected human AREc32 reporter cell line, we found that copper and other transition metals enhanced induction of ARE-driven luciferase by 2- tert -butyl-1,4-hydroquinone (tBHQ) as a result of increased oxidation to 2- tert -butyl-1,4-benzoquinone (tBQ). Following exposure to tBHQ for 30 min, ARE-luciferase activity measured after 24 hr was dependent on the presence of Cu 2+ . In contrast, tBQ-induced activity was Cu 2+ -independent. The metal-catalyzed oxidation of tBHQ to tBQ occured rapidly and stoichiometrically. Compounds that share para - or ortho -hydroquinone structures, such as catechol estrogens, dopamine, and l-DOPA, also induced ARE-driven luciferase in a Cu 2+ -dependent manner. Thus, the oxidation of para- and ortho -Hydroquinones to quinones represents the rate-limiting step in the activation of Nrf2.
Xiliang Luo - One of the best experts on this subject based on the ideXlab platform.
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Carbon nanotube doped poly(3,4-ethylenedioxythiophene) for the electrocatalytic oxidation and detection of hydroquinone
Sensors and Actuators B: Chemical, 2013Co-Authors: Guiyun Xu, Beibei Li, Xiliang LuoAbstract:A sensitive amperometric sensor for the selective detection of hydroquinone in cosmetics was developed based on the excellent electrocatalytic property of carbon nanotube (CNT) doped poly(3,4- ethylenedioxythiophene) (PEDOT) conducting polymer toward the oxidation of hydroquinone. The oxidation potential of hydroquinone on the PEDOT/CNT modified carbon paste electrode was much lower than that on the bare electrode, and the charge transfer rate constant for the oxidation of hydroquinone was significantly increased from 0.45 to 1.84 s -1 after the modification with PEDOT/CNT. Under optimal conditions, the differential pulse voltammetry current of the sensor was linear with hydroquinone concentration across a 1.1-125 μM range and associated with a detection limit of 0.3 μM. Significantly, the detection limit is comparable or better than many current electrochemical hydroquinone assays, and the sensor is potentially much cheaper and easier for fabrication. The sensor was capable not only of comfortably quantifying hydroquinone in the presence of common interferences but also doing this in real cosmetics samples with satisfying accuracy. © 2012 Elsevier B.V. All rights reserved.
Carmine Iodice - One of the best experts on this subject based on the ideXlab platform.
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Avarol derivatives as competitive AChE inhibitors, non hepatotoxic and neuroprotective agents for Alzheimer's disease
European Journal of Medicinal Chemistry, 2016Co-Authors: Giuseppina Tommonaro, Nuria García-font, Carmine Iodice, Sixta Cañadas, Boris Pejin, Rosa Maria Vitale, José Marco-contelles, María Jesús Oset-gasqueAbstract:Avarol is a marine sesquiterpenoid hydroquinone, previously isolated from the marine sponge Dysidea avara Schmidt (Dictyoceratida), with antiinflammatory, antitumor, antioxidant, antiplatelet, anti-HIV, and antipsoriatic effects. Recent findings indicate that some thio-avarol derivatives exhibit acetylcholinesterase (AChE) inhibitory activity. The multiple pharmacological properties of avarol, thio-avarol and/or their derivatives prompted us to continue the in vitro screening, focusing on their AChE inhibitory and neuroprotective effects. Due to the complex nature of Alzheimer's disease (AD), there is a renewed search for new, non hepatotoxic anticholinesterasic compounds. This paper describes the synthesis and in vitro biological evaluation of avarol-3′-thiosalicylate (TAVA) and thiosalycil-prenyl-Hydroquinones (TPHs), as non hepatotoxic anticholinesterasic agents, showing a good neuroprotective effect on the decreased viability of SHSY5Y human neuroblastoma cells induced by oligomycin A/rotenone and okadaic acid. A molecular modeling study was also undertaken on the most promising molecules within the series to elucidate their AChE binding modes and in particular the role played by the carboxylate group in enzyme inhibition. Among them, TPH4, bearing a geranylgeraniol substituent, is the most significant Electrophorus electricus AChE (EeAChE) inhibitor (IC50 = 6.77 ± 0.24 μM), also endowed with a moderate serum horse butyrylcholinesterase (eqBuChE) inhibitory activity, being also the least hepatotoxic and the best neuroprotective compound of the series. Thus, TPHs represents a new family of synthetic compounds, chemically related to the natural compound avarol, which has been discovered for the potential treatment of AD. Findings prove the relevance of TPHs as a new possible generation of competitive AChE inhibitors pointing out the importance of the salycilic substituents on the hydroquinone ring. Since these compounds do not belong to the class of alkaloids, which are notorious for their capability to inhibit AChE while exhibiting side effects, they may constitute novel active AChE inhibitors with fewer side effects.
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biological effects of prenylated Hydroquinones structure activity relationship studies in antimicrobial brine shrimp and fish lethality assays
Journal of Natural Products, 1994Co-Authors: Salvatore De Rosa, Alfonso De Giulio, Carmine IodiceAbstract:: Twenty-three hydroquinone and quinone derivatives were assayed for antimicrobial effects and brine shrimp and fish lethalities, to establish relevant structure-activity relationships (SAR). Linear 2-prenyl-1,4-Hydroquinones used for bioassay were obtained either by isolation from the sponge Ircinia spinosula or by synthesis. Corresponding quinones, as well as Hydroquinones possessing saturated side-chains composed of one to eight isopentane units, were also synthesized and biologically evaluated. Terpenoid 1,4-benzoquinones displayed moderate antimicrobial activity against three microorganisms, SAR studies indicate the optimum length of the side-chain is in the range of five to fifteen carbon atoms.
T M Penning - One of the best experts on this subject based on the ideXlab platform.
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mechanism based inactivation of cox 1 by red wine m Hydroquinones a structure activity relationship study
Journal of Natural Products, 2004Co-Authors: Lawrence M Szewczuk, T M PenningAbstract:: Resveratrol (1) is a m-hydroquinone found in red wine, which has antiinflammatory, cardiovascular protective (antiplatelet), and cancer chemopreventive properties. It is a potent peroxidase-dependent mechanism-based inactivator of COX-1, a desired target for antiplatelet agents, and has no similar effect on COX-2. Much attention has focused on resveratrol (1) as being the sole agent responsible for the cardioprotective effects associated with red wine consumption (commonly known as the "French paradox"). In this study we show that other red wine constituents, namely, the catechins (2, 3) and epicatechins (4, 5), act as peroxidase mediated mechanism-based inactivators of COX-1 but not of COX-2. Structure-activity relationships identify these agents as being as effective as resveratrol with respect to their ability to specifically inactivate COX-1. We show that resorcinol (6) is the minimum structure necessary for mechanism-based inactivation of COX-1. These findings imply that resveratrol is not the sole agent responsible for the antiplatelet activity of red wine and suggest that all dietary m-Hydroquinones should be examined for cardioprotective effects.
