Nonheme Oxovanadium(Ⅴ,Ⅳ) Complexes Catalyze the Oxidative Cleavage of Catechols

It was found that the oxovanadium(V) complex of triethanolamine (TEA) exhibits catalytic activity to the oxidative cleavage of catechols. On the other hand. the vanadyl nitrilotriacetic acid (NTA) complex is inactive. but leads to the formation of stable ternary complex. The main products of the catalytic oxidative cleavage of 3.5-di-tert-butylcatechol were separated and characterized. Based on the results. a reaction mechanism was discussed

A DFT Study on Intramolecular Hydrogen Bond in Substituted Catechols and Their Radicals

Density functional theory (DFT) at B3LYP/6-31G(d,p) level was employed to calculate intramolecular hydrogen bond enthalpies (HIHB), O-H charge differences, O-H bond lengths and bond orders for various substituted catechols and their radicals generated after H-abstraction. It was found that although the charge difference between hydrogen-bonded H and O played a role in determining HIHB, HIHB was mainly governed by the hydrogen bond length. As the oxygen-centered radical has great tendency to form a chemical bond with the H atom, hydrogen bond lengths in catecholic radicals are systematically shorter than those in catechols. Hence, the HIHB for the former are higher than those for the latter.

In vitro polymerization of the dopamine-borate melanin precursor:A proof-of-concept regarding^(10)boron neutron-capture therapy for melanoma

The^(10)boron neutron-capture therapy(BNCT)is an emerging antitumoral method that shows increasing biomedical interest.BNCT is based on the selective accumulation of the^(10)boron isotope within the tumor,which is then irradiated with low-energy thermal neutrons,generating nuclear fission that produces 7lithium,4helium,andγrays.Simple catechol-borate esters have been rather overlooked as precursors of melanin biosynthesis,and therefore,a proof-of-concept approach for using dopamine-borate(DABO)as a suitable boron-containing candidate for potential BNCT is presented here.DABO can spontaneously oxidize and autopolymerize in vitro,giving a soluble,eumelaninlike brown-black poly-DABO product.Melanotic melanoma cell cultures treated with 1 mM DABO for 24 and 48 h were viable and showed no signs of damage or cell death.The stability and possible trans-esterification of DABO is shortly discussed.Chemical calculations and quantitative structure-activity relationships(QSAR)analysis of DABO and the BNCT agent BPA indicated that they should be cell permeant and accumulate within lysosomes and melanosomes.Molecular modeling allows visualization of both the DABO precursor and the structure of a borate derivative of the proposed catechol-porphycene model for eumelanin,showing interesting features from molecular orbital calculations.The main difference between DABO and other agents,such as BPA,is that it is not a boronic acid nor a boron cluster.This simple catechol-borate ester(protected from oxidation and blackening)could be administrated to living cells and organisms,in which biosynthesis of boron-melanin in melanoma melanocytes can lead to improved BNCT.

Optimization of extraction method for quantitative analysis of Si/Al in soil phytoliths

Elemental information carried by phytoliths plays a crucial indicative role in geochemical research.For instance,it serves as an indicator of the carbon pool effect in phytoliths and aids in the elucidation of silicon sources.However,early extraction methods for soil phytoliths primarily focused on obtaining their morphological and quantitative information,lacking efficient techniques for quantitative elemental analysis.In this study,we aimed to extract Si/Al information from soil phytoliths.Considering the need for complete extraction of phytolith,six extraction methods were developed and further by alkaline dissolution to determine Si/Al.Six methods were compared in terms of enrichment capacity,the weight of extracted phytoliths,and Si/Al differences.The results indicated that the addition of Ammonia-Catechol in the commonly used heavy liquid flotation method effectively improved phytolith extraction capability and the accuracy of Si/Al results.Additionally,the inclusion of an acetic acid step before alkaline dissolution further removed surface-adsorbed impurities and enhanced the analytical quality of Si/Al in phytolith.The comparison of the data in this study with other published data shows that our method is relatively robust.The improved method proposed in this study can provide a new idea for the quantitative analysis of other elements in soil phytoliths.

人血浆儿茶酚胺及其代谢产物的高效液相色谱——电化学检测法

血浆儿茶酚胺包括去甲肾上腺素、肾上腺素和多巴胺,由交感神经、肾上腺體质合成与释放,是神经递质之一,调节生理功能的重要物质。因此、测定人血浆中儿茶酚胺(catechol amine,CA)含量有着十分重要的意义,可作为临床某些疾病如嗜铬细胞瘤、类癌瘤等的诊断与预测工具。国内外有关CA测定方法报道甚多,有荧光分光光度计法、放射酶法。

鼠尿中儿茶酚胺荧光测定法

儿茶酚胺(Catecholamine),又名邻苯二酚胺,当交感—肾上腺系统活动增强时,尿中此类化合物的排出量显著增加。人尿中儿茶酚胺测定已有较多方法,而大鼠尿中儿茶酚胺测定未见报道,本文根据三羟基吲哚法原理建立的大鼠尿中儿茶酚胺荧光测定法特异性高,操作简便、使用仪器简单。现将方法介绍如下。

Characterization and phylogenetic analysis of a phenanthrene-degrading strain isolated from oil-contaminated soil

Bacterium strain EVA17 was isolated from an oil-contaminated soil, and identified as Sphingomonas sp. based on analysis of 16S rDNA sequence,cellular fatty acid composition and physiological-chemical tests. The salicylate hydroxylase and catechol 2,3-dioxygenase(C23O) were detected in cell-free lysates, suggesting a pathway for phenanthrene catabolism via salicylate and catechol. Alignment showed that both of the C23O and GST genes of the strain EVA17 had high similarity with homologues of strains from genus Sphingomonas. The phylogenetic analysis based on 16S rDNA and C23O gene sequence indicated that EVA17 should be classified into genus Sphingomonas, although the two phylogenetic trees were slightly different from each other. The results of co-amplification and sequence determination indicated that GST gene should be located upstream of the C23O gene.

Lignin depolymerization for phenolic monomers production by sustainable processes

Biomass wastes(almond shell and olive tree pruning) were used in this work as raw materials for the extraction of high purity lignin by different delignification methods. A pretreatment stage was carried out to remove the major hemicelluloses content in the solid feedstocks. Afterward, two sulfur-free pulping processes(soda and organosolv) were applied to extract the largest fraction of lignin. The extracted lignin contained in the liquors was isolated using selective precipitation methods to design a tailor-made technique for obtaining high-purity lignin(in all cases more 90% of purity was reached). Soda process allowed the extraction of more lignin(around 40%–47%) than organosolv process(lower than 20%) regardless of the lignocellulosic source employed.Once the different lignin samples were isolated and characterized, they were depolymerized for the obtaining of small phenolic compounds. Three main streams were produced after the reaction: phenolic enriched oil, residual lignin and coke. After the purification of these fractions, their quantifications and characterization were conducted.The most abundant product of the reaction was residual lignin generated by the undesirable repolymerization of the initial lignin with yields around 30%–45%. The yield of the stream enriched in phenolic oil was higher than 20%. Coke, the lowest added-value product, presented a yield lower than 12% in all the cases. Lignin from organosolv presented higher phenolic oil yields, mainly due to their lower molecular size. This parameter was, thus, considered a key factor to obtain higher yields.

Fluorescence quenching method for the determination of catechol with gold nanoparticles and tyrosinase hybrid system

The determination method of catechol by fluorescence quenching was developed.The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction.In the presence of tyrosinase,the fluorescence of gold nanoparticles was quenched by catechol which can be employed to detect catechol.Under the optimal conditions,a linear range 5.0×10^(-7)-1.0×10^(-3) mol L^(-1) and a detection limit 1.0×10^(-7) mol L^(-1) of catechol were obtained.o-Quinone intermediate produced...

Vapour-phase O-methylation of Catechol with Methanol on Ti-containing Phosphate Catalysts

Ti-containing phosphate（ Ti-P-O ） catalysts with different molar ratios of P to Ti （0--2. 0 ） were synthesized and characterized by XRD, N2-adsorption/desorption, IR and temperature-programmed desorption （TPD） methods. The catalytic properties of Ti-P-O samples in the vapor-phase O-methylation of catechol with methanol were also studied. The catechol conversion increases with the increase of the molar ratio of P to Ti in a range of 0-0. 33, while a further increase in the P content leads to a decrease of the catalytic activity. Meanwhile, the selectivities of the catalysts to the main product（guaiacol） increase gradually with the increase of the molar ratio of P to Ti. The presence of relatively strong Lewis acidic and/or basic sites in the P-free catalyst should be responsible for the formation of C-alkylation products. The weak acid-base characteristics of the catalysts are favourable for the mono-O-methylation of catechol. In comparison with the Lewis acidic sites, the Bronsted acidic sites on the catalysts are more active for the title reaction.

Characterization and Catalytic Activity of Titanium-containing Aluminum Phosphate Prepared by Sol-gel and Nonuniform Precipitation for O-Alkylation of Catechol with Ethanol

Three titanium-containing aluminum phosphate catalysts with a general formula Al 0.77 Ti 0.23 PO 4 were prepared by the sol-gel method at room temperature(APTS), and a nonuniform precipitation procedure at room temperature(APTR) and under reflux(APTF), respectively. The structural features and the surface properties of the three catalysts were determined by means of the physical adsorption of nitrogen at liquid N 2 temperature, XRD, UV-Vis, NH 3-TPD and IR of adsorbed pyridine. The vapor phase O-alkylation of catechol with ethanol over the prepared catalysts was studied. It was found that the activity and the selectivity of these catalysts are greatly dependent on the preparation method, and catalyst APTF shows the highest activity and selectivity. The characterization evidence indicates that the weak Brnsted acid sites were more effective for the reaction.

Hydroxylation Reaction of Phenol to Catechol on Lanthanide-Zirconia Catalyst

The selective H2O2 oxidation reaction of phenol to catechol on Ln-ZrO2 catalyst has improved the selectivity to 85%, to compare with the conventional titania catalyst. With addition of rare earth such as lanthanum, neodymium, to zirconia as catalyst, the selectivity is increased by 72% and 60% respectively in comparison with the bare titania catalyst.

Phenol Biodegradation by <i>Corynebacterium glutamicum</i>Encapsulated in Electrospun Fibers

In Northern Israel, olive mills discharge liquid waste causing contamination of subterranean aquifers with phenol, rendering them albeit temporarily, unfit for both drinking and irrigation. The impact of groundwater pollution due to phenol spillage can be extensive. We developed a model system for the biodegradation of phenol-contaminated wastewater by the bacterium Corynebacterium glutamicum. Experiments consisting of suspended cultures demonstrated the native ability of this organism to utilize phenol for its metabolic pathways enabling degradation, at levels of nearly 100 ppm within 24 hours. With the use of bioinformatic data, a complete degradation pathway was constructed. Quantitative Real Time PCR analysis of the first two enzymes in this pathway revealed very distinct expression patterns and two different regulation mechanisms were postulated. Additionally, an electrospinning core-shell system was used to assemble electrospun microtubes containing bacteria on porous metallic carriers. We used these carriers as a new immobilization technique and demonstrated their significant phenol degrading capacity in a batch bioreactor configuration. This system demonstrates the feasibility of constructing a water treatment system for the management of phenol-contaminated water.

STUDIES ON STEPWISE STABILITY CONSTANTS OF COORDINATION COMPOUNDS FROM SULFONATED SHEOAK TANNIN WITH METAL IONS

The stepwise stability constants of coordination compounds from sulfonatedsheoak tannin with metal ions have been determined by pH potential method with catechol asmodel compounds at 20℃and constant ionic strength.

Hyphenated LC-ABTS$t and LC-DAD-HRMS for simultaneous analysis and identification of antioxidant compounds in Astragalus emarginatus Labill.extracts

The compounds in leaf and stem extracts of Astragalus emarginatus Labill.(AEL),a plant species used in traditional Lebanese medicine,were investigated for antioxidant properties.First,the activity of various extracts was assessed using the Trolox equivalent antioxidant capacity,oxygen radical absorption capacity,and 2,2-diphenyl-1-picryl-hydrazyl-hydrate assays.The extract obtained using 30%ethanol showed the greatest activity.The antioxidant compounds in this extract were screened using a hyphenated high-performance liquid chromatography-2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonate)radical(ABTS$t)system before being separated by ultra-high-performance liquid chromatography and identified using high-resolution mass spectrometry and ultra-violet-visible diode array detection.Approximately 40 compounds were identified.Hydroxycinnamates(caffeic,ferulic,and p-coumaric acid derivatives)and flavonoids(quercetin,luteolin,apigenin,and isorhamnetin derivatives)were the two main categories of the identified compounds.The active compounds were identified as caffeic acid derivatives and quercetin glycosides.In addition,the catechol moiety was shown to be key to antioxidant activity.This study showed that AEL is a source of natural antioxidants,which may explain its medicinal use.

An Efficient Synthesis of Aromatic 1-Hydroxymethylene-1, 1-bisphosphonates from Aldehydes

A simple and efficient procedure for synthesis of 1-hydroxymethylene-1,1-bisphos- phoates from aldehydes is described. This method was applied to the synthesis of novel catechol substituted bisphosphonates as the anti-osteoporosis agents.

SYNTHESIS OF POLYCATECHOL WITH ELECTROCHEMICAL ACTIVITY AND ITS PROPERTIES

The electrochemical polymerization of catechol on platinum has been carried out using repeated potential cycling between -0.2 and 1.1 V (versus SCE). The electrolytic solution consisted of 0.2 mol dm(-3) catechol, 0.5 mol dm(-3) NaCl and 0.1 mol dm(-3) Na2HPO4 with pH 8.72. Catechol can not be polymerized at pH greater than or equal to 10.12. Polycatechol has an electrochemical lactivity at pH less than or equal to 4. The anodic and cathodic peak potentials of polycatechol shift towards more negative values as the pH of the solution increases from 1 to 4. The electrochemical activity of polycatechol hardly changes in this pH region, but it decreases slowly with time. This is caused by oxygen in air, which leads to an irreversible oxidation of polycatechol. This property is favorable for protecting metals from corrosion. Raman and FTIR spectra of polycatechol and catechol are quite different. AFM images of polycatechol films provide evidence that the image of the oxidized state of polycatechol is markedly different from that of the reduced one. This difference is caused by doping and dedoping of polycatechol.

Catechol-Bisphosphonate Conjugates: New Potential Chelating Agents for Metal Intoxication Therapy

In a quest for better chelating therapy drugs for the treatment of intoxication by Fe, Al, oractinides, two new series of mixed catechol-bisphosphonate through amide linkage were synthesized.Benzyl group was used as protecting group to avoid the breakage of amide by acid hydrolysis orimcomplete reaction in silylation-dealkylation using bromotrimethylsilane.

THE CONSTRUCTION OF AN EBV-xy1E SHUTTLE VECTOR SYSTEM FOR THE STUDY OF MUTATI0N IN MAMMALIAN CELLS

The Pseudomonas putida TOL plasmid gene xy1E,whichproduces catechol 2,3-dioxygenase （CatO2ase;catechol:oxygen 2,3-oxidoreductase （decyclizing）,EC 1.13.11.2 ）was used as a target gene to study the mechanisms ofmutation and induced mutation frequency in

Synthesis and Characterization of Model Complexes of Catechol Dioxygenases Supported by the Anionic Hydrotris-3,5-dimethyl-pyrazolylborate Ligand

An iron（Ⅲ） complex [Fe^Ⅲ（Tpz^Me2）（Hpz^Me2）Cl2]（1） has been synthesized at a low temperature, which contains tripodal ligand, namely, the anionic hydrotris-3,5-dimethyl-pyrazolylborate（Tpz^Me2）. A series of iron（Ⅲ） catecholate complexes 2-5 has been obtained via the reaction of compound 1 with catecholate or substituted catecholates. These complexes were characterized by X-ray crystallographic analysis, mass spectrometry and elemental analysis, and the results show that TpzMe2 ligand has the beneficial effect on the stabilization of iron（Ⅲ） catecholate complexes.