490-79-9Relevant articles and documents
Dioxygen reactivity of iron(ii)-gentisate/1,4-dihydroxy-2-naphthoate complexes of N4 ligands: Oxidative coupling of 1,4-dihydroxy-2-naphthoate
Rahaman, Rubina,Munshi, Sandip,Banerjee, Sridhar,Chakraborty, Biswarup,Bhunia, Sarmistha,Paine, Tapan Kanti
, p. 16993 - 17004 (2019)
The influence of supporting ligands and co-ligands on the dioxygen reactivity of a series of iron(ii) complexes, [(6-Me3-TPA)FeII(GN-H)]+ (1), [(6-Me3-TPA)FeII(DHN-H)]+ (1a), [(BPMEN)FeII(GN-H)]+ (2), [(BPMEN)FeII(DHN-H)]+ (2a), [(TBimA)FeII(GN-H)]+ (3), and [(TBimA)FeII(DHN-H)]+ (3a) (GN-H2 = 2,5-dihydroxybenzoic acid and DHN-H2 = 1,4-dihydroxy-2-naphthoic acid) of N4 ligands, is presented. The iron(ii)-gentisate complexes react with dioxygen to afford the corresponding iron(iii) species. On the contrary, DHN-H undergoes oxidative C-C coupling to form [2,2′-binaphthalene]-1,1′,4,4′-tetrone 3-hydroxy-3′-carboxylic acid (BNTHC) on 1a, and [2,2′-binaphthalene]-1,1′,4,4′-tetrone 3,3′-dicarboxylic acid (BNTD) on 2a and 3a. In each case, the reaction proceeds through an iron(iii)-DHN species. The X-ray single crystal structures of [(6-Me3-TPA)FeII(BNTD)] (1Ox) and [(BPMEN)FeII(BNTD)] (2Ox) confirm the coupling of two DHN-H molecules. The formation of iron(iii) product without any coupling of co-ligand from the complexes, [(BPMEN)FeII(HNA)]+ (2b) and [(BPMEN)FeII(5-OMeSA)]+ (2c) (HNA = 1-hydroxy-2-naphthoate, 5-OMeSA = 5-methoxysalicylate) confirms the importance of para-hydroxy group for the coupling reaction. The unusual coupling of DHN-H by the iron(ii) complexes of the neutral N4 ligands is distinctly different from the oxygenolytic aromatic C-C cleavage of DHN by the iron(ii) complex of a facial N3 ligand.
Formation of oxygen radicals in solutions of different 7,8- dihydropterins: Quantitative structure-activity relationships
Oettl, Karl,Pfleiderer, Wolfgang,Reibnegger, Gilbert
, p. 954 - 965 (2000)
Under certain conditions, 7,8-dihydroneopterin in aqueous solution promotes hydroxyl-radical formation. Thus, we investigated the stimulation of hydroxyl-radical formation by ten different 7,8-dihydropterins (=2-amino-7,8- dihydropteridin-4(1H)-one), i.e., 6-(1'-hydroxy) derivatives 1 and 2, methyl derivatives 3-7, and 6-(1'-oxo) derivatives 8-10. All but the 6-(1'-oxo) derivatives produced hydroxyl radicals, as measured by the amount of salicylic acid hydroxylation products. This amount was dependent on the stability of the dihydropterin used. In the presence of chelated iron ions, hydroxylation was increased in every case; even 6-(1'-oxo) derivatives showed a low hydroxylation of salicylic acid. The degree of increase, however, strongly depended on the side chain of the dihydropterin. The 7,8- dihydroneopterin (2) was investigated in more detail. Iron ions influenced both, the stability of 2 and hydroxyl-radical formation. While iron ions determined the kinetics of the reaction, the amount of 2 was responsible for the amount of hydroxyl radicals formed. Our data establish that promotion of hydroxyl-radical formation by 7,8-dihydropterins depends on the oxidizability of the dihydropterins and on their iron-chelating properties.
A chlorogenic acid esterase from a metagenomic library with unique substrate specificity and its application in caffeic and ferulic acid production from agricultural byproducts
Gui, Lun,Long, Qizhang,Yao, Jian
, (2021/08/25)
Soil microbes are an abundant source of enzymes with unique properties that may be useful for industrial applications. As most wild-type strains show low chlorogenic acid esterase expression and activity, and most microbes cannot be cultured in the laboratory, a metagenomic approach provides methods of identifying new enzymes. In this study, a gene encoding a chlorogenic acid esterase, named Tan410, was isolated from a soil metagenomic library and overexpressed in Escherichia coli BL21 (DE3). The recombinant enzyme, with a predicted molecular weight of 54.88 kDa, was purified to homogeneity. The K m and V max values for Tan410 were 1.26 mM and 0.33 mM min–1, respectively, with chlorogenic acid as the substrate. Its optimum temperature and pH for reaction were 30 °C and 7.5, respectively. The enzyme exhibited moderate thermostability and broad pH stability (3.0–10.0). Tan410 was also able to hydrolyse ethyl ferulate, methyl caffeate, propyl gallate, ethyl gallate, methyl vanillate, methyl benzoate, ethyl benzoate, methyl 2,5-dihydroxybenzoate, and methyl 3,5-dihydroxybenzoate, and it released caffeic and ferulic acids from agricultural byproducts (destarched wheat bran and coffee pulp). Tan140 has potential for industrial application in biomass valorization.
Black TiO2 nanotube arrays decorated with Ag nanoparticles for enhanced visible-light photocatalytic oxidation of salicylic acid
Plodinec, Milivoj,Gr?i?, Ivana,Willinger, Marc G.,Hammud, Adnan,Huang, Xing,Pan?i?, Ivana,Gajovi?, Andreja
, p. 883 - 896 (2018/11/10)
Novel forms of black TiO2 nanotubes-based photocatalysts for water purification were prepared. Two features were combined: decoration of TiO2 nanotube arrays with Ag nanoparticles (sample TiO2-NT's@Ag) and further hydrogenation of this material (TiO2-NT's@Ag-HA). Obtained photocatalysts show high efficiency for degradation of salicylic acid, a typical water-borne pollutant. The photocatalysts considerably exceed the photocatalytic properties of TiO2 nanotubes and commercial TiO2 P25 taken as a reference for modeling of the photocatalytic process. The comparison of photocatalytic activities between novel photocatalyst was based on a numerical approach supported by the complex kinetic model. This model allowed a separate study of different contributions on overall degradation rate. The contributions include: salicylic acid photolysis, photocatalysis in UVB, UVA and in the visible part of applied simulated solar irradiation. The superior photocatalytic performance of the photocatalyst TiO2-NT's@Ag-HA, particularly under visible irradiation, was explained by the combined effect of a local surface plasmon resonance (LSPR) due to Ag nanoparticles and creation of additional energy levels in band-gap of TiO2 due to Ti3+ states at nanotube surfaces. The presence of Ag also positively influence charge separation of created electron-holes pairs. The synergy of several effects was quantified by a complex kinetic model through the factor of synergy, fSyn. Stability testing indicated that the catalysts were stable for at least 20 h. The novel design of catalysts, attached on Ti foils, presents a solid base for the development of more efficient photocatalytic reactors for large-scale with a long-term activity.
Evidence for the electrochemical production of persulfate at TiO2 nanotubes decorated with PbO2
Santos, José Eudes L.,Antonio Quiroz, Marco,Cerro-Lopez, Monica,De Moura, Dayanne Chianca,Martínez-Huitle, Carlos A.
, p. 5523 - 5531 (2018/04/02)
It is well known that PbO2-based electrodes are considered to be non-active anodes, producing higher concentrations of hydroxyl radicals in aqueous solutions, and consequently, favouring the electrochemical degradation of organic pollutants. However, no evidence has been reported on the production of persulfates using this kind of electrode in sulphate aqueous solutions. For this reason, the aim of this work is to prepare (by an electrochemical procedure (anodization and electrodeposition)) and characterize (by X-ray diffraction, scanning electron microscopy, and potentiodynamic measurements) Ti/TiO2-nanotubes/PbO2 disk electrodes (with a geometrical area of 65 cm2) in order to evaluate the electrochemical production of persulfate using Na2SO4 solution as the support electrolyte and applying current densities of 7.5 and 60 mA cm-2, as well as the influence of the electrosynthesis of hydroxyl radicals, in concomitance. The results clearly showed that significant production of hydroxyl radicals and persulfate is achieved at the Ti/TiO2-nanotubes/PbO2 surface, but this depends on the current density. The production of OH at the Ti/TiO2-nanotubes/PbO2 surface in Na2SO4 solution was confirmed by a RNO spin trapping reaction. The results were compared with those of a Ti/Pt electrode in order to understand the effect when a lower amount of OH is produced at the active anode surface. Based on the results, the Ti/TiO2-nanotubes/PbO2 anode could exhibit good electrocatalytic properties for environmental applications involving persulfate oxidants.
HPLC study on Fenton-reaction initiated oxidation of salicylic acid. Biological relevance of the reaction in intestinal biotransformation of salicylic acid
Nyúl, Eszter,Kuzma, Mónika,Mayer, Mátyás,Lakatos, Sándor,Almási, Attila,Perjési, Pál
, p. 1040 - 1051 (2018/10/24)
Fenton-reaction initiated in vitro oxidation and in vivo oxidative biotransformation of salicylic acid was investigated by HPLC-UV-Vis method. By means of the developed high performance liquid chromatography (HPLC) method salicylic acid, catechol, and all the possible monohydroxylated derivatives of salicylic acid can be separated. Fenton oxidations were performed in acidic medium (pH 3.0) with two reagent molar ratios: (1) salicylic acid: iron: hydrogen peroxide 1:3:1 and (2) 1:0.3:1. The incubation samples were analysed at different time points of the reactions. The biological effect of elevated reactive oxygen species concentration on the intestinal metabolism of salicylic acid was investigated by an experimental diabetic rat model. HPLC-MS analysis of the in vitro samples revealed presence of 2,3- and 2,5-dihydroxybenzoic acids. The results give evidence for nonenzyme catalysed intestinal hydroxylation of xenobiotics.
Complete Enzymatic Oxidation of Methanol to Carbon Dioxide: Towards More Eco-Efficient Regeneration Systems for Reduced Nicotinamide Cofactors
Kara, Selin,Schrittwieser, Joerg H.,Gargiulo, Serena,Ni, Yan,Yanase, Hideshi,Opperman, Diederik J.,Van Berkel, Willem J. H.,Hollmann, Frank
supporting information, p. 1687 - 1691 (2015/06/02)
A novel system for in situ regeneration of reduced nicotinamide cofactors (NADH) is proposed: through a cascade of alcohol dehydrogenase (ADH), formaldehyde dismutase (FDM) and formate dehydrogenase (FDH) complete oxidation of methanol to carbon dioxide (CO2) is coupled to the regeneration of NADH. As a consequence, from one equivalent of methanol three equivalents of NADH can be obtained. The feasibility of this cascade is demonstrated at the examples of an NADH-dependent reduction of conjugated C=C-double bonds (catalysed by an enoate reductase) and the NADH-dependent hydroxylation of phenols (catalysed by a monooxygenase). The major limitation of the current regeneration system is the comparably poor catalytic efficiency of the methanol oxidation step (low kcat and high KM value of the ADH used) necessitating higher than theoretical methanol concentrations.
Aromatic hydroxylation of salicylic acid and aspirin by human cytochromes P450
Boji?, Mirza,Sedgeman, Carl A.,Nagy, Leslie D.,Guengerich, F. Peter
, p. 49 - 56 (2015/04/14)
Aspirin (acetylsalicylic acid) is a well-known and widely-used analgesic. It is rapidly deacetylated to salicylic acid, which forms two hippuric acids - salicyluric acid and gentisuric acid - and two glucuronides. The oxidation of aspirin and salicylic acid has been reported with human liver microsomes, but data on individual cytochromes P450 involved in oxidation is lacking. In this study we monitored oxidation of these compounds by human liver microsomes and cytochrome P450 (P450) using UPLC with fluorescence detection. Microsomal oxidation of salicylic acid was much faster than aspirin. The two oxidation products were 2,5-dihydroxybenzoic acid (gentisic acid, documented by its UV and mass spectrum) and 2,3-dihydroxybenzoic acid. Formation of neither product was inhibited by desferrioxamine, suggesting a lack of contribution of oxygen radicals under these conditions. Although more liphophilic, aspirin was oxidized less efficiently, primarily to the 2,5-dihydroxy product. Recombinant human P450s 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4 all catalyzed the 5-hydroxylation of salicylic acid. Inhibitor studies with human liver microsomes indicated that all six of the previously mentioned P450s could contribute to both the 5- and 3-hydroxylation of salicylic acid and that P450s 2A6 and 2B6 have contributions to 5-hydroxylation. Inhibitor studies indicated that the major human P450 involved in both 3- and 5-hydroxylation of salicylic acid is P450 2E1.
General method for the synthesis of salicylic acids from phenols through palladium-catalyzed silanol-directed C-H carboxylation
Wang, Yang,Gevorgyan, Vladimir
, p. 2255 - 2259 (2015/02/19)
A silanol-directed, palladium-catalyzed C-H carboxylation reaction of phenols to give salicylic acids has been developed. This method features high efficiency and selectivity, and excellent functional-group tolerance. The generality of this method was demonstrated by the carboxylation of estrone and by the synthesis of an unsymmetrically o,o′-disubstituted phenolic compound through two sequential C-H functionalization processes.
Effect of oxidants on photoelectrocatalytic decolourization using α-Fe2O3/TiO2/activated charcoal plate nanocomposite under visible light
Ayoubi-Feiz, Baharak,Aber, Soheil,Sheydaei, Mohsen
, p. 19368 - 19378 (2015/04/14)
The present study is to investigate the effect of oxidants H2O2, S2O82-, BrO3-, ClO3- and IO4- with different concentrations on photoelectrocatalytic decolourization of Lanasol yellow 4G (LY4G) as a model contaminant using α-Fe2O3/TiO2/activated charcoal plate (ACP) nanocomposite under visible light. In this system, the decolourization efficiency increased with increasing BrO3-, ClO3- and IO4- doses but reached an optimum amount with H2O2 and S2O82- at 1 mM. Experimental data revealed that the decolourization rate of LY4G in all of the processes obeyed pseudo-first-order kinetics. Total organic carbon (TOC) results indicated that 21% and 100% of organic substrate were mineralized respectively after 80 min and 8 h. The gas chromatography-mass spectrometry (GC-MS) analysis was employed to identify the intermediate products. Also, a plausible degradation pathway was proposed. Finally, the real wastewater treatment was investigated by chemical oxygen demand (COD) measurements. This journal is
