Bioaccessibility of Zinc from Yogurt and Determination of Total Concentration Using Slurry Sampling and Flame Atomic Absorption Spectrometry
The bioaccessibility of Zn during in vitro gastrointestinal digestion from yogurt was investigated. In addition, the methodologies of sample preparation (dry and wet digestion, and slurry sampling) for the determination of total concentration of Zn in yogurt by flame atomic absorption spectrometry were also compared in this work. In comparison with digestion procedures, the proposed slurry sampling is simple and less time-consuming procedure. The limit of quantification determined was 1.3 µg g-1. The concentrations of Zn in the Brazilian yogurt ranged from 3.40 to 5.62 µg g-1. The percentage of the bioaccessibl...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

High Throughput Mass Spectrometry Platform for Prospecting High Value Chemicals from Bioconversion of Glycerin
We describe advantages of DIMS and its combined application with chemometrics towards an untargeted metabolomics approach to analyze several samples in a short time (11 samples per h). Three batches with 34 samples from the bioconversion of glycerin using several filamentous fungi strains were analyzed. Batch 347 was selected as promising, since high value chemicals, such as amide, phenolic and acid compounds, were identified. The platform presented was fast, robust, and versatile, then it could be applied to different bioprocesses. (Source: Journal of the Brazilian Chemical Society)
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Transmissive to Dark Electrochromic and Fluorescent Device Based on Poly(fluorene-bisthiophene) Derivative
Films of a poly(fluorene-bisthiophene) derivative, named PFBT, were electrodeposited onto indium tin oxide (ITO) electrodes and their electrochromic and fluorescence properties were investigated. Such films displayed color variation from yellow, in the neutral state, to green, in the oxidized state, as shown by tracking of the CIE (Commission Internationale de l ’ Eclairage) 1931 xy chromaticity coordinates. PFBT films are fluorescent in the neutral state (E = 0.0 V vs. Ag/Ag+) with emission at 532 nm; however, upon oxidation at 0.85 V the photoluminescence intensity is significantly decreased. A solid-state electroc...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Analysis of the Seasonal Variation in Chemical Profile of Piper glabratum Kunth Essential Oils Using GC×GC/qMS and Their Antioxidant and Antifungal Activities
In this study, chemical composition, antioxidant and antifungal activities of essential oils (EOs) from leaves of P. glabratum were investigated. The influence of seasonality on its chemical composition was also evaluated. The chemical characterization was performed by two-dimensional gas chromatography coupled with quadrupole mass spectrometry (GC ×GC/qMS). Altogether, 199 compounds were identified in the EOs and their composition varied during the seasonal cycle. The main compounds found were sesquiterpenes and their oxygenated analogues. EOs showed antioxidant activity, measured by 2,2-diphenyl-1-picrylhydrazyl-DP...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Nanoparticles of Fe2O3 and Co3O4 as Efficient Electrocatalysts for Oxygen Reduction Reaction in Acid Medium
This paper presents a comparative study about the oxygen reduction reaction (ORR) catalyzed by nanoparticles of Fe2O3 and Co3O4 applied on the surface of glassy carbon electrodes (GCE). The nanoparticles were synthesized using the modified polymeric precursor method (Pechini). These two nanomaterials were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) techniques. The estimated average particle sizes were 21 and 31 nm for Fe2O3 and Co3O4, respectively. Electrochemical impedance spectroscopy (EIS) showed that Fe2O3/GCE has lower charge transfer resistance than Co3O4/GCE. The surfa...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Structure and Absolute Configuration of Secondary Metabolites from Two Strains of Streptomyces chartreusis Associated with Attine Ants
The antibiotic streptazolin (1), its E-isomer (2), along with the stereoisomers strepchazolin A (3) and strepchazolin B (4) and the inorganic compound cyclooctasulfur (5) were produced in solid culture by Streptomyces chartreusis ICBG377, which was isolated from the fungal garden of the leaf-cutter ant Acromyrmex subterraneus brunneus. This is the first time compound 2 is reported as a natural product. Compound 5, which showed antagonist activity against the specialized pathogenic fungus Escovopsis sp., was also produced by Streptomyces chartreusis ICBG323, isolated from the exoskeleton of winged male of Mycocepurus goeldi...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Silica/Titania Graphite Composite Modified with Chitosan and Tyrosinase Employed as a Sensitive Biosensor for Phenolic Compounds
A mesoporous, high surface area and conductive silica/titania graphite composite modified with chitosan and functionalized with tyrosinase was prepared. The composite was obtained by the sol-gel method and the surface of the resultant material was modified with chitosan solutions containing 5, 10 and 15% by mass. The textural characterization showed that even after modification with chitosan, the composite maintains a pore volume near 0.70 cm3 g-1 and pore diameter between 10 and 50 nm, adequate for enzyme immobilization. The tyrosinase was immobilized on the composite that was modified with 5% chitosan solution. A carbon ...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Light Response of Three Water-Soluble MnI PhotoCORMs: Spectroscopic Features and CO Release Investigation
Currently, there is great interest in the study of water-soluble metal compounds capable of releasing carbon monoxide, due to their potential therapeutic use. This paper reports the synthesis, spectroscopic characteristics and CO release properties of three water-soluble manganese(I) carbonyl compounds [Mn(aaz)(CO)3]Br (1; where aaz = 6-amino-6-methylperhydro-1,4-diazepine), [Mn(Me2aaz)(CO)3]Br (2; where Me2aaz = 6-amino-1,4,6-trimethyl-1,4-diazacycloheptane) and [Mn(tacn)(CO)3]Br (3; where tacn = 1,4,7-triazacyclononane), that can act as photoCORMs (where CORM is carbon monoxide-releasing molecule). The main aim was to pr...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Photochemical Synthesis of Ag and Au Nanoparticles Using a Thioxanthone Substituted Chitosan as Simultaneous Photoinitiator and Stabilizer
Silver (AgNPs) and gold (AuNPs) nanoparticles in aqueous solution were generated and stabilized using the 10-oxo-10H-dibenzene thiopyran-3-4-dicarboximide chitosan (TXICh) macrophotoinitiator. The photoinitiator and the nanoparticles in aqueous solution were characterized by UV-Vis spectroscopy and transmission electron microscopy (TEM). Pure TXICh in aqueous solution forms self-assembled particles with diameter around 30 nm. AgNPs were prepared using TXICh in the presence and absence of triethanolamine (TEOH). During irradiation, a broad band in the range of 410-415 nm was observed, corresponding to the plasmon absorption...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Cardol-Derived Organophosphorothioates as Inhibitors of Acetylcholinesterase for Dengue Vector Control
Aedes aegypti is the main vector of three neglected tropical diseases: dengue, zika and chikungunya. Dengue is under surveillance by health organizations worldwide due to the risk of epidemics. Since there is no specific treatment for dengue, most studies have focused on preventing the reproduction and/or development of the mosquitoes. We studied the larvicidal activity of five phosphates and phosphorothioates derived from cardol, one of the four main components of cashew nut shell liquid (Anacardium occidentale L.), at different concentrations. The organophosphorothioate derivatives were tested for their in vitro inhibito...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Interplay between Near-Field Properties and Au Nanorod Cluster Structure: Extending Hot Spots for Surface-Enhanced Raman Scattering
Materials science has observed a continuous increase in the use of metal nanoparticles in a wide range of studies, from fundamental physics to technological applications such as photocatalysis and optical communication devices. This broad scope has the same fundamental origin, the localized surface plasmons, whose excitation leads to strong light confinement, especially in the vicinity of closely spaced nanoparticles, the hot spots. The field amplification may be used to amplify the Raman scattering of adsorbed molecules, which is known as surface-enhanced Raman scattering (SERS). A crucial and limiting characteristic of S...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Kaolinite/TiO2/cobalt(II) Tetracarboxymetallophthalocyanine Nanocomposites as Heterogeneous Photocatalysts for Decomposition of Organic Pollutants Trimethoprim, Caffeine and Prometryn
S ão Simão ’ s Brazilian kaolinite has been treated with titanium(IV) isopropoxide and cobalt(II) tetracarboxymetallophthalocyanine under different conditions (acidic or basic), leading, after drying at 100 ºC, to new titania-doped cobalt(II)-metallophthalocyanine/kaolinite solids. These solids were characterized by chemical analysis, powder X-ray diffraction, Fourier transform infrared spectroscopy, thermal analyses and nitrogen adsorption. No significant changes were observed by diffractometry, but the specific surface area depended of the synthetic route followed. The ability of these solids for...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Nanostructured Systems Obtention Using LbL Self-Assembly or the Cysteine-Assisted Adsorption Method and Their Application as a Water Splitting Single Catalyst
The present work evaluated the effect on charge transfer in functionalized TiO2 nanostructured systems using different binders. We highlight the conditions required to form self-assembled systems by varying the number of layers, as well as by substituting them for an organic binder, cysteine. Additionally, we study the pH effect of the precursor solution (HAuCl4) on gold nanoparticles (AuNPs) formation. The morphological characterization allowed us to determine the percentage of Au atoms on the surface of the synthesized nanoparticles. Inductively coupled plasma mass spectrometry (ICP-MS) analysis determined the amount of ...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Synthesis of Hybrid Monolithic Columns Using a Click Chemistry Reaction for Application in Capillary Liquid Chromatography
Hybrid monolithic columns present characteristics of both silica and organic monoliths, such as good mechanical properties, wide pH tolerance, high permeability and stability and little swelling or shrinkage. A common way to prepare this type of material is by using alkoxysilanes and organic monomers via the sol-gel process and click chemistry reactions. In this paper, a co-condensation organic-silica hybrid monolith was prepared based on tetramethoxysilane (TMOS) and vinyltrimethoxysilane (VTMS) as precursors for the sol-gel process. The hybrid monolithic matrix was modified with dodecanethiol through the thiol-ene click ...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Feasibility of a New Method for Identification and Discrimination of Gunshot Residues by Total Reflection X-Ray Fluorescence and Principal Component Analysis
This study aims at identifying and discriminating gunshot residue (GSR) from conventional ammunition of six different calibers by total reflection X-ray fluorescence (TXRF) and pattern recognition by principal component analysis (PCA). GSR samples were collected from hands of volunteer shooters with swabs moistened with deionized water and were extracted with 5% v v-1 nitric acid. Aliquots were deposited on quartz disks for further determination by TXRF of the elements Al, S, Ca, K, Mn, Fe, Ni, Cu, Zn, Br, Sr, Sb, Ba and Pb, whose concentrations were imported into the MATLAB ® software for PCA execution. The method pro...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Multi-Energy Calibration: A Practical Method for Determination of Macro and Micro Nutrients in Meat by ICP OES
The multi-energy calibration (MEC) was evaluated for the determination of Ca, Cu, Fe, K, Mg, Na, P, S, and Zn in meat samples by inductively coupled plasma optical spectrometry (ICP OES). This calibration method consists of using only two calibration standards and several atomic and ionic emission wavelengths with different sensitivities to determine the analyte concentration in the sample. Both calibration mixtures are prepared using the same amount of sample, which contributes to minimize matrix effects. The accuracy was evaluated using two certified reference materials, bovine liver (SRM 1577c) and bovine muscle (SRM 84...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Acid Hydrolysis of Regular Corn Starch under External Electric Field
The main objective of the present work is the investigation of a new method for starch hydrolysis. For this, we proposed the acid hydrolysis under the action of an external electric field, able to develop a faster reaction than the conventional one. Corn starch with 18% amylose was subjected to a fixed voltage, varying the external electric field application time and the number of cycles. Morphology, crystallinity, and thermal stability of the starches were investigated by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), and small-angle X-ray scattering (SAXS). The results showed that the acid hydro...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

A New Tetraglycosylated Flavonoid from Leaves of Platycyamus regnellii Benth. Isolated by High-Speed Countercurrent Chromatography
A new tetraglycosylated flavonoid derivative of kaempferol was isolated from the butanol extract of leaves of Platycyamus regnellii (Fabaceae) using high-speed countercurrent chromatography (HSCCC). The butanol extract (960.5 mg) was initially fractionated with the solvent system EtOAC-BuOH-H2O 2:8:10 (v/v/v) (elution in normal phase mode). The fractions containing the major tetraglycosylated flavonoid were further purified with the same solvent system by modifying the ratios to 3:7:10 (v/v/v) and alternating the elution to reversed phase mode. The structure of the isolated flavonoid (48.1 mg, 99.7% purity by ultra-high pe...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

(Bio)conjugation Strategies Applied to Fluorescent Semiconductor Quantum Dots
Quantum dots (QDs) are semiconductor nanocrystals, which present unique photophysical properties, enabling their application as new fluorescent platforms for biomedical sciences. Colloidal QDs are end-capped with organic or inorganic compounds, not only to prevent their agglomeration but also to provide reaction sites for the attachment of targeting (bio)molecules, nanoparticles or other interfaces, for specific biological purposes. The (bio)conjugation can involve non-covalent or covalent interactions, which can be accomplished through different strategies. The final assembly needs to maintain its chemical and optical sta...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

The Research on Porphyrins and Analogues in Brazil: A Small Review Covering Catalytic and other Applications since the Beginning at Universidade de São Paulo in Ribeirão Preto until the Joint Venture between Brazilian Researchers and Colleagues from Universidade de Aveiro, Portugal
The synthetic versatility and the potential applications of porphyrins and analogues in different fields have aroused special interest in their study, especially to mimic biological systems, such as cytochrome P-450. The ability of the porphyrin tetrapyrrolic core to accommodate metal ions of varying charges can modulate the type of application of these compounds. As a contribution, in this special number in honor to the Brazilian women who have devoted their lives to the growth and dissemination of chemistry knowledge, we report the advances in porphyrin research in Brazil for catalytic purposes and other applications, be...
Source: Journal of the Brazilian Chemical Society - October 25, 2019 Category: Chemistry Source Type: research

Physicochemical Study of the Interaction between Gold Nanoparticles and Lipase from Candida sp. (CALB): Insights into the Nano-Bio Interface
The surface interactions between gold nanoparticles (AuNPs) and lipase from Candida antarctica fraction B (CALB) were investigated at macromolecular and colloidal length-scales. In order to elucidate the reciprocal effect of the interactions on the individual component ’ s properties, CALB was either added during the synthesis of AuNPs or added to pre-synthesized AuNPs. In both cases, it was observed that the AuNPs are spherical and stable and, by fluorescence and circular dichroism spectroscopies, changes were observed in the secondary and tertiary structure of CALB, that were dependent on the AuNPs concentration. N...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Compatibility of GROMOS-Derived Atomic Parameters for Lipopolysaccharide Membranes with the SPC/E Water Model and Alternative Long-Range Electrostatic Treatments Using Single Nonbonded Cutoff and Atom-Based Charge Schemes
Recent developments of GROMACS v.2016 ceased to support methodological approaches used in the development and validation of the GROMOS force field. We investigated the performance of a previously developed extension of the GROMOS force field for lipopolysaccharides to reproduce the structural dynamics of bacterial outer membrane (OM) using a single cutoff for nonbonded interactions and atom-based charge truncation. We further compared this setup for use with reaction field (RF) or particle mesh Ewald (PME) approximations in the presence of simple point charge (SPC) and extended simple point charge (SPC/E) water models. We ...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Facile One-Step Electrodeposition Fabrication of Amorphous MoS2 Catalysts in Titanium for Hydrogen Evolution Reaction
Hydrogen is seen as a future energy carrier that will assist the global energy fuel demand. However, it is still necessary to study efficient and inexpensive catalysts that can be used on a large scale to make this technology practical. In this paper the electrodeposition of molybdenum disulfide (MoS2) film on titanium (Ti) substrate was performed by cyclic voltammetry and the film was evaluated for hydrogen evolution reaction (HER). The deposition optimized conditions was 25 cycles and 4 mmol L-1 (NH4)2[MoS4] in 0.1 mol L-1 NaClO4 solution. The film was characterized from X-ray diffraction (XRD), scanning electron microsc...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Thermal Stability and Kinetic of Decomposition of Mono- and Dicationic Imidazolium-Based Ionic Liquids
Phase transitions, thermal stability, thermokinetics and activation parameters of degradation reaction of the dicationic ionic liquids (ILs), 1,n-bis(3-methylimidazolium-1-yl)alkane ([BisAlk(MIM)2][2Br]) and monocationic ILs, 1-(3-methylimidazolium-1-yl)alkane ([Alk(MIM)][Br]), where Alk = Dec, DoDec, TetDec, (decane, dodecane, tetradecane) were evaluated. The influence of an additional cationic head and the alkyl chain length in thermal parameters were also evaluated. The dicationic ILs are more stable than monocationic and thermal degradation of ILs mono- and dicationic did not show linear dependence on the alkyl chain l...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Chlorine and Fluorine Determination in Eye-Pencil: Development of an Eco-Friendly Sample Preparation Method for Ion Chromatography Analysis
In this paper, a feasible method was proposed for the chlorine and fluorine determination in eye-pencil samples using ion chromatography (IC). The microwave-induced combustion (MIC) was used to digest up to 200 mg of a sample, with 50 mg of microcrystalline cellulose as a combustion aid and only water for analytes absorption. Cl and F recoveries were 105 ± 1 and 93 ± 5%, respectively, when standard solutions were used in the recovery tests. Certified reference materials (CRM) were also digested mixed to the sample, and no significant difference between the obtained results and the certified values was observe...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Catalytic Transformation Conditions of Ethanol on Dealuminated BEA Zeolites
Catalysis is an important tool in obtaining a range of derivative products from renewable sources, such as ethanol. Solid-state dealumination using ammonium hexafluorosilicate on the BEA zeolite under the treatment at temperature of 190 °C, 70 mol% dealumination in the presence of humidity and washing with buffer solution at 25 °C generated larger pores. The absence of washing procedure for the same sample resulted in pore blockage. Ethanol dehydration reactions showed conversion of 72% (64% ethylene and 8% diethyl ether) for thi s sample at 300 °C and high weight hourly space velocity (WHSV, 3247 h-1), whereas...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Degradation of Acid Red 8 Dye Using Photo-Fenton Reaction Mediated by Titanium Modified Catalysts
Catalysts prepared by co-precipitation of iron and titanium were evaluated in heterogeneous photo-Fenton degradation of the azo dye Acid Red 8 under blacklight irradiation. Materials with different titanium contents (0
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Gold Catalysis for Selective Hydrogenation of Aldehydes and Valorization of Bio-Based Chemical Building Blocks
Gold catalysts are best known for their selectivity in oxidation reactions, however, there is a promising future for gold in selective hydrogenations. Herein, the hydrogenation of several aldehydes and important bio-based chemical building blocks, namely 5-hydroxymethylfurfural (5-HMF), furfural and vanillin, was performed throughout the combination of Au nanoparticles with Lewis bases. The Au-amine ligand (e.g., 2,4,6-trimethylpyridine) catalytic system could reduce the aldehyde carbonyl group selectively, without reducing alkene moieties or opening the furanic ring that occur on most traditional catalysts. Otherwise, the...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Linear Peptide Analogues from Jatropha’s Orbitides Promote Migration of Human Neonatal Foreskin Fibroblasts in vitro and Collagen Deposition
Orbitides are a class of small naturally occurring cyclic peptides with structural and functional diversities. Their chemical properties make this class feasible to be obtained by solid phase peptide synthesis (SPPS). Therefore, this synthetic accessibility enables useful application and facilitates the identification of analogues, bioactivity studies, and thus, enables them to be applied to obtain peptide libraries. The aim of this work was to investigate the effects of orbitides and their linear synthetic analogues on the migration of neonatal human foreskin fibroblasts. The screening of linear peptide analogues, origina...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Oxone®-Promoted One-Pot Synthesis of 1-Aryl-4-(organylselanyl)-1H-pyrazoles
We describe herein an efficient protocol for the one-pot synthesis of 4-organylselanylpyrazoles by direct cyclocondensation and C-H bond selenylation reactions starting from hydrazines, 1,3-diketones and diorganyl diselenides promoted by Oxone ®. The products were obtained through a metal catalyst free methodology, under mild conditions, in short reaction times and moderate to excellent yields. (Source: Journal of the Brazilian Chemical Society)
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Determination of Amino Acids in Plasma Samples of Preeclampsia Patients by Liquid Chromatography Coupled to High-Resolution Mass Spectrometry
This work presents the application of a simple and sensitive method developed for the simultaneous analysis of the levels of twenty two underivatizated free L-amino acids in plasma samples of preeclampsia patients by high performance liquid chromatography coupled to high-resolution mass spectrometer (LC-HRMS) using hydrophilic interaction liquid chromatography (HILIC) silica column. The linearity was evaluated in the range of 0.009 to 8.018 µmol L-1 showing coefficients of determination (R2) in the range of 0.999 to 0.911 (p
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Tianeptine Esters Derivatives: A Study of Protein-Drug Interaction Performed by Fluorescence Quenching and Molecular Docking
The nature of binding between bovine serum albumin (BSA) and the antidepressant tianeptine and a new series of esters derivatives were studied in this paper. The interactions with BSA were investigated by UV-Vis and fluorescence spectroscopy at three different temperatures. The fluorescence quenching experiments showed that BSA interactions with tianeptine could be dynamic while to its esters a static mechanism was observed. The results showed that tianeptine quenches the intrinsic fluorescence of BSA more efficiently than its esters due to the presence of the free acid portion. The number of binding sites determined by fl...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Are Imidazoles Versatile or Promiscuous in Reactions with Organophosphates? Insights from the Case of Parathion
Is the broad mechanistic versatility of imidazole towards organophosphates (OPs), that has inspired many catalysts and sensors, beneficial? Herein, a thorough analysis is given seeking to unravel this puzzle. For OPs from the P=O family, imidazole attacks the phosphorus atom exclusively (N-phosphorylates). With the P=S family which are less reactive, an unusual N-alkylation predominates. Surprisingly, imidazole reacts with methyl parathion exclusively at the aliphatic carbon, whilst for the ethylated analogue parathion, imidazole reacts by two pathways: at both the phosphorus and aliphatic carbon, with predominance for the...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Direct Assay to Evaluate Phosphoenolpyruvate Carboxykinase Activity
Phosphoenolpyruvate carboxykinase (PEPCK) is a ubiquitous enzyme found in all known groups of organisms, acting in the reversible conversion of oxaloacetate (OAA) to phosphoenolpyruvate (PEP) in the presence of divalent metal ion, and dependent of adenosine 5 ’ -triphosphate (ATP) or guanosine-5 ’ -triphosphate (GTP). PEPCK is an important enzyme in the metabolism of some organisms, such as Trypanosoma cruzi, being suggested as a potential drug target to treat Chagas ’ disease. Its catalytic activity is, classically, measured by coupled assays. Herein, a direct assay by liquid chromatography-tandem mass s...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Iridium-Based Catalysts for the Ethanol Electrooxidation in Acidic Media
Herein we sinthesize and investigate Ir-based nanocatalysts (dispersed in carbon) in different atomic compositions combining two (IrRh) and three metals (IrRhSn). These materials were evaluated towards the ethanol electrooxidation in acidic electrolyte in presence of three ethanol concentrations using cyclic voltammetry, while the species produced during the reaction were monitored by in situ Fourier transform infrared spectroscopy (FTIR). Results show that IrRh binary electrocatalysts are selective to the production of CO2 from ethanol, but the catalytic activity is poor. This finding is interpreted in terms of a slow ads...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Integrated Chemometric Approach to Optimize Sample Preparation for Detecting Metabolic Changes Provoked by Abiotic Stress in Coffea arabica L. Leaf Fingerprints
The effects of water-deficit stress on irrigated and unirrigated field plants of Coffea arabica L. genotype IAPAR 59 were investigated. Plant extracts were obtained following an ethanol-dichloromethane-hexane statistical mixture design. Proton nuclear magnetic resonance (1H NMR) fingerprints of the extracts were discriminated using factor analysis (FA) and hierarchical clustering techniques. Extracts from the 1:1:1 ternary mixture presented the largest discriminations compared with those from the pure solvents or their 1:1 binary mixtures. Metabolites resulting from fermentation processes and nutritional deficiencies as we...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Electrode Modified with the Ionic Liquid [P6,6,6,14+]2[MnCl42-] for the Determination of Bisphenol A in Plastic Samples
This paper describes a new and simple electrode for the determination of bisphenol A (BPA) in different plastic samples using carbon paste electrode (CPE) modified with a trihexyltetradecylphosphonium tetrachloromanganate(II) ([P6,6,6,14+]2[MnCl42-]) magnetic ionic liquid (MIL/CPE). Electrochemical characterization of MIL/CPE by cyclic voltammetry and electrochemical impedance spectroscopy indicated that MIL facilitated the electron transfer. Using squarewave voltammetry (SWV) under optimized conditions, the calibration curve showed a linear range for BPA from 2.0 to 53.0 µmol L-1, with limit of detection (LOD) of 0....
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Gold Nanoparticles and [PEDOT-Poly(D,L-Lactic Acid)] Composite: Synthesis, Characterization and Application to H2O2 Sensing
Biocompatible electrochemical devices are challenging to develop due to the toxicity of many advanced electrode materials and the difficulty to degrade the discarded material. Few recent advances were made in the synthesis of conducting biodegradable composites of polymers for electrode materials. In this article we describe the synthesis of two new inorganic/organic nanocomposites of Au nanoparticles and conducting polymers based on the biodegradable polymer poly(D,L-lactic acid) (PDLLA): Au nanoparticles/oligomers of 3,4-ethylenedioxythiophene (EDOT)-PDLLA and Au nanoparticles with poly(3,4-ethylenedioxythiophene) (PEDOT...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

A New Cytotoxic Naphthoquinone and Other Chemical Constituents of Sinningia reitzii
Phytochemical study of Sinningia reitzii (Gesneriaceae) led to the isolation of three new naphtoquinones, 6,7-dimethoxydunnione, 7-hydroxy-6-methoxydunnione, and 5-hydroxy-6,7-dimethoxydunnione from the tubers, together with four known compounds, 7-hydroxydunnione, 8-hydroxydunnione, 5-hydroxy-6,7-dimethoxy- α -dunnione, and 8-hydroxydeydrodunnione. Aerial parts furnished five known compounds, 5-hydroxy-6,7-dimethoxydunniol, 6,8-dihydroxy-7-methoxy-2-O-methyldunniol, loureirin B, jacaranone, and methyl 4-hydroxyphenylacetate. Compounds 8-hydroxydunnione, 5-hydroxy-6,7-dimethoxy- α -dunnione, 8-hydroxydeydrodunn...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Aspergillus niger: A Hundred Years of Contribution to the Natural Products Chemistry
Aspergillus niger is a phytopathogenic fungus responsible for the plant disease called “ black mold ” , and it is considered the most versatile microorganism for producing acids, proteins, and enzymes of industrial value, besides a variety of compounds of pharmacological interest. This review presents a century of contribution of A. niger in the natural products chemistry under two different perspectives: (i) an overview of the structural diversity of secondary metabolites produced by A. niger from different habitats and their biological activities; (ii) a general discussion of the enzymatic potential of A. nig...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Magneto-Responsive Hydrogels: Preparation, Characterization, Biotechnological and Environmental Applications
Hydrogels are hydrophilic three-dimensional networks able to hold large amount of water and hydrophilic molecules. Magneto-responsive hydrogels comprise of magnetic nanoparticles dispersed in polymeric networks that can be manipulated under external magnetic field. This review aims at (i) giving a brief overview on the evolution of hydrogels until the design and development of magnetic hydrogels; (ii) describing the types of hydrogels and the basic concepts about superparamagnetic iron oxide nanoparticles, as well as the preparation and characterization of magneto-responsive hydrogels; (iii) displaying the relevant applica...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

DNA Damage by Endogenous and Exogenous Aldehydes
The present overview describes the formation of deoxyribonucleic acid (DNA) adducts from endogenous and exogenous aldehydes, such as acetaldehyde, acrolein, crotonaldehyde, malonaldehyde, 4-hydroxy-2-nonenal and 2,4-decadienal. Malonaldehyde reacts with 2 ’ -deoxyguanosine, 2 ’ -deoxyadenosine, and 2 ’ -deoxycytidine, yielding cyclic pyrimidopurinone and acyclic adducts. The direct addition of ɑ , β -unsaturated aldehydes to DNA bases yields cyclic substituted propano adducts, such as 1,N2-propano-2 ’ -deoxyguanosine. Alternatively, ɑ , β -unsaturated aldehydes can be oxidized to reactiv...
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

For Gender Equality in Science
(Source: Journal of the Brazilian Chemical Society)
Source: Journal of the Brazilian Chemical Society - October 22, 2019 Category: Chemistry Source Type: research

Uncured Polydimethylsiloxane as Binder Agent for Carbon Paste Electrodes: Application to the Quantification of Propranolol
This study describes the use of uncured polydimethylsiloxane (PDMS) as a binder agent to prepare carbon paste electrodes (CPEs). A comparative study between the properties of CPEs prepared with PDMS and mineral oil Nujol ®, the most common binder agent for CPEs, was carried out. Cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry showed that PDMS-CPEs presented higher electrical conductivity, active electrochemical area, and wider useful potential window compared with Nujol®-CPEs. Mor eover, PDMS-CPEs were more stable in aqueous mixtures containing 50% (v/v) of ethanol or methanol than...
Source: Journal of the Brazilian Chemical Society - September 17, 2019 Category: Chemistry Source Type: research

Different Strategies to Anchor Organotin Methoxides on Silica and Their (Re)Use as Heterogeneous Catalysts for Transesterification Reactions
Catalysts were prepared by the heterogenization of the tributyltin(IV) methoxide (n-Bu3Sn(OMe)) and dibutyltin(IV) dimethoxide (n-Bu2Sn(OMe)2) on silica by two strategies: (i) anchoring of the organotin(IV) compounds on silica and (ii) anchoring of the organotin(IV) compounds on a silica gel functionalized with mercaptopropyl groups (SiO2 – SH). The characterization results showed that, regardless of the method used to anchor the organotin species, the solids contained approximately 7-10% of Sn. The decrease or disappearance of the O – H and S – H stretching signals in the SiO2 and SiO2 – SH spectra...
Source: Journal of the Brazilian Chemical Society - September 17, 2019 Category: Chemistry Source Type: research

Hydrogen Peroxide Electrogeneration by Gas Diffusion Electrode Modified With Tungsten Oxide Nanoparticles for Degradation of Orange II and Sunset Yellow FCF Azo Dyes
In this work, the gas diffusion electrode (GDE) cathode of Vulcan XC72 carbon modified with nanoparticles of WO2.72 (WO2.72 / Vulcan XC72) was used for H2O2 electrogeneration and degradation of 350 mL of Orange II (OII) and Sunset Yellow FCF (SY) azo dyes by electro-Fenton (EF) and photoelectro-Fenton (PEF) processes with different Fe2+ initial content (1.00, 0.50 and 0.25 mmol L-1). The WO2.72 / Vulcan XC72 GDE electrolyzed approximately 3 times more H2O2 than the Vulcan XC72 GDE. Decolorizations and mineralizations of the dye solutions were more efficient at higher concentrations of Fe2+. The decolorization decay showed ...
Source: Journal of the Brazilian Chemical Society - September 17, 2019 Category: Chemistry Source Type: research

A Study of Chemical Composition and Enzymatic Hydrolysis of Solid Organic Waste from Agrosilvopastoral Systems
Agrosilvopastoral waste, regarding agriculture and agro-industry sectors, is pointed as a promising sustainable raw material for biofuels production, specially concerning exploitation of lignocellulosic organic residues for fermentable sugars and cellulosic ethanol output, being therefore necessary to investigate the potential of these substrates concerning chemical composition, since many of them were not reported yet in literature. Being so, this paper presents a study of chemical composition and enzymatic hydrolysis of wastes from the four main crops in Maranh ão, Brazil (soy, cassava, rice and corn) which are us...
Source: Journal of the Brazilian Chemical Society - September 17, 2019 Category: Chemistry Source Type: research

Square-Wave Voltammetry Determination of Ciprofloxacin in Pharmaceutical Formulations and Milk Using a Reduced Graphene Oxide Sensor
In this paper, a simple, sensitive and precise electroanalytical method was developed using a chemically-reduced graphene-oxide (CRGO)-modified glassy carbon electrode and square wave voltammetry (SWV) for determination of ciprofloxacin in pharmaceutical formulations (tablets) and milk samples. Advantages of this sensor include a potential displacement of 100 mV and a 5-fold current increase for the electrochemical oxidation of ciprofloxacin, which resulted in a highly sensitive sensor, when compared to unmodified electrode. The improved properties of the modified electrode are likely due to the formation of a porous surfa...
Source: Journal of the Brazilian Chemical Society - September 17, 2019 Category: Chemistry Source Type: research

Sulfonated Styrene-Acrylic Acid Copolymers with pH-Indicator Property
In this study, a polymer pH-indicator was synthesized by sulfonation of poly(styrene-co-acrylic acid) with concentrated sulfuric acid. The synthesized polymer pH-indicator exhibited pH-responsive color changes in aqueous solutions, being purple in alkaline medium (pH 9). The sulfonation process extent and polymer color were affected by time and temperature of the process, as well as acrylic acid (AA) content. The addition of acrylic acid was a crucial point for color change due to the facility of cyclic ketone structure to turn into phenol under acidic condition. Compared with low molecule pH-indicators, the sulfonated cop...
Source: Journal of the Brazilian Chemical Society - September 17, 2019 Category: Chemistry Source Type: research

Catalytic Removal of Toluene from Air Streams by Cobalt Oxide Supported on Sepiolite
In conclusion, the results of this study confirmed sepiolite-supported cobalt oxide catalyst as an efficient catalyst for degradation of toluene. (Source: Journal of the Brazilian Chemical Society)
Source: Journal of the Brazilian Chemical Society - September 17, 2019 Category: Chemistry Source Type: research