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Journal of the Brazilian Chemical Society, Volume: 33, Número: 5, Publicado: 2022
  • Determination of 3,4,5-Trihydroxybenzoic Acid Exploiting a Visible-Light-Driven Photoelectrochemical Platform: Application in Wine and Tea Samples Article

    Lima, Kayni C. M. S.; Fernandes, Ridvan N.; Santos, Clenilton C. dos; Damos, Flavio S.; Luz, Rita de Cássia S.

    Resumo em Inglês:

    The present work is based on the development and application of a photoelectrochemical method for the amperometric determination of 3,4,5-trihydroxybenzoic acid in different samples. The method is based on the use of a photoelectrochemical platform based on a glass slide coated with fluorine-doped tin oxide, which has been modified with cadmium sulfide and poly(D-glucosamine) and subjected to a light-emitting diode (LED) lamp. The photoelectrochemical platform was sensitive to the increase of the concentration of the antioxidant 3,4,5-trihydroxybenzoic acid in the solution. Under the optimized experimental conditions, the photoelectrochemical method presented a linear response for a 3,4,5-trihydroxybenzoic acid concentration ranging from 0.2 up to 500 µmol L-1. The method was applied to 3,4,5-trihydroxybenzoic acid determination in samples of wines and teas with recoveries between 95.88 and 101.72%. The results obtained suggest that the developed platform is a promising tool for quantifying the 3,4,5-trihydroxybenzoic acid.
  • Temperature Dependent Emission Properties of ReI Tricarbonyl Complexes with Dipyrido-Quinoxaline and Phenazine Ligands Article

    Ramos, Cristiane L.; Prado, Fernando S.; Carmo, Marcos Eduardo G.; Farias, Giliandro; Souza, Bernardo; Machado, Antonio Eduardo H.; Patrocinio, Antonio Otavio T.

    Resumo em Inglês:

    In this work, the emission properties of fac-[Re(CO)3(NN)(py)]+, NN = 1,10-phenanthroline (phen), dipyrido[3,2-f:2’,3’-h]quinoxaline (dpq) and dipyrido[3,2-a:2’3’-c]phenazine (dppz); py = pyridine were investigated in different temperatures, ranging from 80 to 300 K, and in different solvent mixtures and in polymethyl methacrylate. The changes observed in the emission quantum yields were rationalized based on a two-level excited state model, in which the non-emissive upper state is thermally populated and decays faster than the lowest lying emissive state. fac [Re(CO)3(dpq)(py)]+ is a metal-to-ligand charge transfer (MLCT) emitter as the complex with phen but exhibits smaller emission quantum yields, being more sensitive to the solvent. This behavior was rationalized by quantum-mechanical calculations including the spin-orbit coupling matrix elements, revealing that intersystem crossing from the lowest singlet excited state in fac-[Re(CO)3(dpq)(py)]+ likely occurs to triplet states lying at higher energies. Similar behavior were observed for fac-[Re(CO)3(dppz)(py)]+, although the later exhibits intraligand emission that are strongly quenched in fluid solutions by low-lying MLCT states. The fundamental studies carried out here provide new insights on the excited state dynamics of ReI complexes with dipyrido-quinoxaline and phenazine ligands and can contribute for further advances on their application as luminescent probes.
  • Use of a Portable Microscope Combined with a Smartphone to Determine the Authenticity of Brazilian Banknotes and National Driver’s Licenses Article

    Costa, Rayana A.; Vittorazzi, Bruno V.; Barbosa, Amanda P.; Rocha, Victória B. da; Brandão, Jandira M. O. B.; Lacerda Jr., Valdemar; Filgueiras, Paulo R.; Romão, Wanderson

    Resumo em Inglês:

    This study proposed using a portable microscope combined with a smartphone and application (PhotoMetrix® application) to evaluate the authenticity of Brazilian banknotes (R$50 and R$100) and national driver’s licenses (NDL) through image acquisition (Samsung S7) and chemometric treatment (principal component analysis (PCA)). Six regions of the banknote were analyzed: holographic band; lower and upper tactile regions containing the number referring to the value of the note; microprints above the effigy (obverse); and numbers and the surroundings of the animal formed by microprints (reverse). For NDLs, the regions were the following: the coat of arms of the republic; the state map with microprints; optical ink variation; distorted positive microletters with technical failure; negative guilloche; typographic numbering; micro letter wire; and region with line printing. For the chemometric study with Photometrix®, we selected a region of interest (ROI) of 32 × 32 and 64 × 64 pixels with autoscaled data using the channels red (R), green (G), blue (B), hue (H), saturation (S), value (V), lightness (L) and intensity (I). We obtained excellent results for differentiating banknotes and NDLs, both by visual and chemometric analyses (PCA). This study demonstrates the effectiveness of using a portable microscope and a smartphone as a portable forensic tool that is fast, robust, low-cost and reliable.
  • In vitro Antioxidant and Anticholinesterase Activities of Ouratea fieldingiana (Gardner) Eng. Leaf Extract and Correlation with Its Phenolics Profile with an in silico Study in Relation to Alzheimer’s Disease Article

    Frota, Lucas S.; Alves, Daniela R.; Freitas, Leonardo S.; Lopes, Francisco F. S.; Marinho, Marcia M.; Marinho, Emmanuel S.; Morais, Selene M. de

    Resumo em Inglês:

    Ouratea fieldingiana is a native medicinal plant from Northeastern Brazil and many biological properties are due to the phenolic constituents. The objective of this work was performing the characterization of O. fieldingiana leaf constituents to correlate with antioxidant and anticholinesterase activities by in vitro and in silico studies and thus contribute to find new agents against Alzheimer’s disease. The high-performance liquid chromatography revealed the presence of the flavonoids rutin, isoquercitrin, kaempferol-3-O-rutinoside, quercetin, apigenin and amentoflavone. The antioxidant activities by the (2,2-diphenyl-1-picrylhydrazyl) (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) methodologies, showed good results with half maximal inhibitory concentration (IC50) values ranging from 5.63 to 11.47 µg mL-1 and 2.72 to 23.71 µg mL-1, respectively. Acetylcholinesterase inhibition assay pointed out the flavone apigenin with best activity. Computational studies evaluated the interaction of flavonoids with the enzyme acetylcholinesterase co-crystallized with the galantamine, used as standard. All flavonoids exhibited binding energy greater than that of galantamine, but only apigenin showed strong interaction with the active site of the enzyme and other bind probably to different allosteric centers. Then, O. fieldingiana extract and flavonoids with good anti-radical activity and presenting a broad-spectrum action against acetylcholinesterase (AChE) enzyme ought to be tested in clinical studies to discover new neuro-therapeutic candidates.
  • Thermophysical and Transport Properties of the BaCl2-CsCl High Temperature Ionic Liquid Mixtures Article

    Popescu, Ana-Maria; Constantin, Virgil

    Resumo em Inglês:

    High temperature ionic liquids (HTILs) densities and transport properties for mixtures BaCl2 CsCl, x(BaCl2) = 0-1, have been studied as a function of composition and temperature. In terms of Arrhenius theory, the temperature correlation of all measured properties was made and discussed. Thermodynamic properties (isothermal compressibility, molecular volume, lattice energy, heat capacity, molar Gibbs energy, enthalpy and entropy) were derived for all the studied HTILs from experimental data. The viscosity isotherms show negative deviations from linearity, while conductivity isotherms have positive deviations which may be related to the formation of highly negative changed ion associated species. The evolution of the excess quantities: viscosity deviation (∆η), excess molar viscosity (∆Eη), excess molar conductivity (∆Eκ), show a very good parallelism. The linear behavior between conductivity and viscosity was determined using the fractional Walden rule and the average slope was found far from unity.
  • Novel Greener Microwave-Assisted Deprotection Methodology for the 1,3-Dioxolane Ketal of Isatin Using Calix[n]arenes Article

    Barbosa, Lucas B.; Silva, Tiago L. da; Rezende, Michelle J. C.; Silva, Bianca N. M. da; Guzzo, Rodrigo N.; Silva, Bárbara V.

    Resumo em Inglês:

    In this work, the combined use of p-sulfonic acid-calix[n]arene and microwave energy to hydrolyze the 1,3-dioxolane ketal of isatin was evaluated with excellent results. This is the first time that p-sulfonic acid-calix[n]arene has been used as the catalyst in a ketal hydrolysis reaction and the deprotection of the ketone carbonyl of isatin is reported. The presence of 2.5 mol% of p-sulfonic acid-calix[4,6]arene at 160 ºC resulted in over 96% conversion of this ketal in 10 min, with the additional advantage of using water as a solvent. This catalytic system (aqueous phase containing p-sulfonic acid-calix[4]arene) was reused for five consecutive cycles, with a conversion above 96% maintained. This reusable system is not practicable using p-toluenesulfonic acid and p-hydroxybenzenesulfonic acid as catalysts since both are extracted to the organic phase with the reaction product. The hydrolysis of 1,3-dioxolane ketal of isatins with different substituents (CH3, I, Br, Cl, F, NO2) in the aromatic ring was also evaluated. The protecting group of 5-methyl-isatin was removed with 73% conversion using 2.5 mol% of p-sulfonic acid-calix[4]arene at 160 ºC for 5 min. In contrast, the ketal of 5-nitro-isatin reached 80% conversion using the same conditions after 40 min.
  • Validation and Application of a Methodology for Quantifying Levels of Parabens in Sports Supplements from Brazil Using Liquid Chromatography-Mass Spectrometry Article

    Rocha, Bruno A.; Cesila, Cibele A.; Martins, Airton C.; Souza, Marília C. O.; Barbosa Jr., Fernando

    Resumo em Inglês:

    Although parabens have been reported to be used as antimicrobial preservatives in personal care products, pharmaceuticals, and foodstuffs, little is known about the occurrence of these compounds in sports supplements. In this study, a simple, fast and sensitive liquid chromatography tandem mass spectrometry method for simultaneous determination of five commonly used parabens, methyl-, ethyl-, propyl-, butyl-, and benzylparaben in sports supplements was established. The analytical method was validated with the values of parameters being acceptable. The method proved reliable, accurate, and sensitive and was successfully applied for the quantitation of parabens in 85 sports supplements samples. Almost all sports supplements contained at least one of the parabens analyzed, and the total concentrations of five parabens ranged from below the limit of quantification to 145 μg g-1, with a median value of 0.171 μg g-1. Ethylparaben and methylparaben were the most frequent paraben analogs found in samples (detection rate > 60%). Propylparaben, butylparaben and benzylparaben are forbidden in food samples, their detection rates were 49.4, 21.2 and 4.7%, respectively. Therefore, our study suggests that Brazilian population may be exposed to estrogenic not allowed parabens and their harmful effects through the intake of sports food supplements.
  • Natural and Semisynthetic Triterpenes from Combretum leprosum Mart. with Antiplasmodial Activity Article

    Passarini, Guilherme M.; Ferreira, Amália S.; Moreira-Dill, Leandro S.; Zanchi, Fernando B.; Jesus, Aurileya G. de; Facundo, Valdir A.; Teles, Carolina B. G.

    Resumo em Inglês:

    Malaria is responsible for thousands of deaths each year. Currently, artemisinin combination therapy (ACT) is used as first-choice medication against the disease. However, the emergence of resistant strains prompts the search for alternative compounds. The present study aimed to investigate the antiplasmodial activities of natural triterpenes (compounds 1 and 2), and semisynthetic derivatives 1a, 1b, 1c, and 1d. Antiplasmodial assays were carried out using the SYBR Green technique, whereas cytotoxicity was evaluated by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method. Hemolytic assays were performed on human erythrocytes. An in silico analysis of the compounds against PfENR (Plasmodium falciparum 2-trans-enoyl-reductase) was carried out by molecular docking. Experiments with 1, and its derivatives against P. falciparum showed that 1a was very similar in terms of biological activity to compound 1 (half maximal inhibitory concentration (IC50) ca. 4 µM), whereas 1b, 1c, and 1d had reduced antiplasmodial activities (IC50 between 8-103 µM). The selectivity indexes of 1 and 1d for HepG2, and Vero cells were > 10. Docking results partially agreed with the in vitro experiments, with 1 and 1c having the best and worst affinities with PfENR, respectively. In conclusion, the results showed that 1 and 1d may serve as biotechnological tools in the development of antimalarial drugs.
  • Catalytic Effects of Ruthenocene Bimetallic Compounds Derived from Fused Aromatic Ring Ligands on the Main Oxidizing Agent for Solid Rocket Motor Article

    Dibdalli, Yuvaraja; Gaete, José; Osorio-Gutierrez, Claudio; Arroyo, Juan Luis; Norambuena, Angel; Amshumali, Mungalimane K.; Abarca, Gabriel; Morales-Verdejo, Cesar

    Resumo em Inglês:

    We report the catalytic effect of three ruthenocene bimetallic compounds derived from fused aromatic rings of general formula [{Cp*Ru}2L], with Cp*: pentamethylcyclopentadiene and L = pentalene (1), 2,6-diethyl-4,8-dimethyl-s-indacene (2), and 2,7-diethyl-as-indacene (3), on the thermal decomposition of ammonium perchlorate (AP). The new compound 3 was characterized by a combination of multinuclear magnetic resonance (NMR) spectroscopy and elemental analysis. The differential scanning calorimetry (DSC) analysis of compound 3 shows a decrease in the decomposition temperature of AP to 347 ºC, increases the energy release to 2048 J g-1 and, consequently, leads to the lowest activation energy (42.9 kJ mol-1). These results are comparable to the typically used metallocene (catocene: 347 ºC and 2472 J g-1), suggesting a suitable and competitive alternative to be used as a modifier for composite solid propellants.
  • Development of a Disposable Pipette Extraction Method Using Coffee Silverskin as an Adsorbent for Chromium Determination in Wastewater Samples by Solid Phase Extraction Article

    Silva, Weida R.; Costa, Bruno E. S.; Batista, Alex D.; Alves, Vanessa N.; Coelho, Nivia M. M.

    Resumo em Inglês:

    A procedure using disposable pipette tips adapted for solid-phase extraction, known as DPX SPE, was used as an alternative way for the chromium determination in wastewater samples. DPX-SPE consists of a device which allows a dynamic contact between the sample and the solid-phase. A residue obtained from the processing of coffee beans, denominate coffee silverskin, was used as a new adsorbent. Characterization techniques revealed properties of lignocellulosic materials with potential application for chromium adsorption. The parameters including adsorbent mass (25.00 mg), elution solvent (0.1 mol L-1 HCl, 200 μL) and pH (2.0) were optimized. Thus, 1.00 mL of deionized water for conditioning, 4.00 mL of sample, 2 extraction cycles and 1 elution cycle were the employed conditions. Enrichment factor of 12, limit of detection of 6.00 µg L-1 and relative standard deviation (RSD) 1.3% (n = 3) were obtained. The method proved to be fast, cheap, environmentally friendly, and simple, providing good recoveries (104-113%), and it was satisfactorily applied in real samples.
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