303-38-8Relevant articles and documents
Hydroxyl Radicals quantification by UV spectrophotometry
Peralta,Roa,Hernandez-Servin,Romero,Balderas,Natividad
, p. 137 - 141 (2014)
Hydroxilation of aromatic compounds is an oxidative process that has been employed as indirect method to quantify the produced hydroxyl radicals during an advanced oxidation process (a-OH). This is usually complicated by the radical high reactivity and short life time and therefore a scavenging agent such as salicylic acid is commonly employed. This usually implies a rather sophisticated analytical method such as chromatography. In this work, however, a relatively simple and low cost method is proposed to achieve the aforementioned objective. This method is based on UV-Vis spectrophotometry and was employed to quantify the hydroxyl radicals produced during the electrochemical oxidation of water when employing a platinum anode in a galvanostatic type process. Salicylic acid was employed as a-OH scavenger. The concentration of the hydroxilated resulting products, 2,3-dihidroxybenzoic Acid and 2,5-dihydroxibenzoic Acid, was determined by UV-Vis Spectroscopy and utilized to quantify the hydroxyl radicals. In addition, mineralization was followed by Chemical Oxygen Demmand measurements.
PHOTOCHEMICAL HYDROXYLATION OF SALICYLIC ACID DERIVATIVES WITH HYDROGEN PEROXIDE, CATALYZED WITH Fe(III) AND SENSITIZED WITH METHYLENE BLUE
Lunak, Stanislav,Muzart, Jacques,Brodilova, Jirina
, p. 905 - 912 (1994)
Substitution of hydrogen in the carboxy or hydroxy group of a salicylic acid molecule with a methyl group, which hinders the coordination of Fe(III), results in a pronounced reduction of photocatalytic effects.The complex of Fe(III) with salicylic acid is the precursor of the thermal catalyst arising on irradiation.
Gentisides A and B, two new neuritogenic compounds from the traditional Chinese medicine Gentiana rigescens Franch
Gao, Lijuan,Li, Jinyou,Qi, Jianhua
, p. 2131 - 2134 (2010)
Two new alkyl 2,3-dihydroxybenzoates, gentisides A and B, were isolated from the traditional Chinese medicine Gentiana rigescens Franch. Their structures and stereochemistry were elucidated by spectroscopic methods and chemical derivatization. These compounds showed a significant neuritogenic activity at 30 μM against PC12 cells that was comparable to that seen for the best nerve growth factor (NGF) concentration of 40 ng/mL. Gentisides A and B showed parallel activity, indicating that the observed structural difference at the end of their alkyl chain did not affect neuritogenic activity.
Photochemical hydroxylation of salicylic acid with hydrogen peroxide; mechanistic study of substrate sensitized reaction
Lang, Kamil,Brodilova, Jirina,Lunak, Stanislav
, p. 1729 - 1737 (1996)
The photochemical hydroxylation of salicylic acid (SA) by hydrogen peroxide proceeds via the same intermediate independently of the excited reactant (i.e. SA or H2O2). This conclusion is supported by the similar effect of pH on the quantum yields and on the isomer ratio of formed products: 2,3-dihydroxybenzoic acid (2,3-DHB) and 2,5-dihydroxybenzoic acid (2,5-DHB). The product ratio ([2,3-DHB]/[2,5-DHB]) is not affected by H2O2 concentration.
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)
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.
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.
Biocatalytic carboxylation of phenol derivatives: Kinetics and thermodynamics of the biological Kolbe-Schmitt synthesis
Pesci, Lorenzo,Glueck, Silvia M.,Gurikov, Pavel,Smirnova, Irina,Faber, Kurt,Liese, Andreas
, p. 1334 - 1345 (2015/04/14)
Microbial decarboxylases, which catalyse the reversible regioselective ortho-carboxylation of phenolic derivatives in anaerobic detoxification pathways, have been studied for their reverse carboxylation activities on electron-rich aromatic substrates. Ortho-hydroxybenzoic acids are important building blocks in the chemical and pharmaceutical industries and are currently produced via the Kolbe-Schmitt process, which requires elevated pressures and temperatures (≥ 5 bar, ≥ 100 °C) and often shows incomplete regioselectivities. In order to resolve bottlenecks in view of preparative-scale applications, we studied the kinetic parameters for 2,6-dihydroxybenzoic acid decarboxylase from Rhizobium sp. in the carboxylation- and decarboxylation-direction using 1,2-dihydroxybenzene (catechol) as starting material. The catalytic properties (Km, Vmax) are correlated with the overall thermodynamic equilibrium via the Haldane equation, according to a reversible random bi-uni mechanism. The model was subsequently verified by comparing experimental results with simulations. This study provides insights into the catalytic behaviour of a nonoxidative aromatic decarboxylase and reveals key limitations (e.g. substrate oxidation, CO2 pressure, enzyme deactivation, low turnover frequency) in view of the employment of this system as a 'green' alternative to the Kolbe-Schmitt processes. Microbial decarboxylases are known to catalyze the reversible regioselective ortho-carboxylation of phenolic derivatives in anaerobic detoxification pathways. In order to get new insights into the catalytic action and to resolve bottlenecks in view applications, we studied the kinetics of 2,6-dihydroxybenzoic acid decarboxylase from Rhizobium sp. in the carboxylation- and decarboxylation-direction, correlating the data according to a reversible random bi-uni mechanism.
IMPROVED PROCESS FOR PREPARATION OF 2,3-DIHYDROXY BENZONITRILE
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, (2014/02/15)
Disclosed is one pot process of the preparation of 2,3-dihydroxy benzonitrile from 2,3-dialkoxy benzoic acid without prior isolation of the intermediates. Further disclosed is the preparation of 2,3-dihydroxy benzonitrile by dealkylation of 2,3-dialkoxy benzonitrile using suitable aluminum salt-amine complex.
