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Journal of the Brazilian Chemical Society, Volume: 27, Número: 12, Publicado: 2016
  • Synthesis, Antitubercular and Leishmanicidal Evaluation of Resveratrol Analogues Articles

    Coimbra, Elaine S.; Santos, Juliana A.; Lima, Larissa L.; Machado, Patrícia A.; Campos, Débora L.; Pavan, Fernando R.; Silva, Adilson D.

    Resumo em Inglês:

    In this paper we continue our efforts in the search for new Schiff bases as resveratrol analogues as promising antitubercular and antileishmanial agents. Compounds were evaluated in vitro against Mycobacterium tuberculosis and Leishmania species. Compounds showed varying activity against promastigotes of all Leishmania species tested (concentration leading to reduction of 50% of parasite growth-IC50 values ranging from 1.60 to 15.53 µg mL-1). Majority of compounds exhibited good results against Leishmania species with IC50 values below 10.00 µg mL-1, with no cytotoxicity against macrophages. One of the analogues showed the best activity against amastigotes of L. amazonensis (IC50 = 5.73 µg mL-1). Furthermore, the compounds showed comparable or better effect than drugs commonly used in tuberculosis treatment such as Cycloserine®. The analogue that was the most active for M. tuberculosis had minimal inhibitory concentration MIC90 = 0.78 µg mL-1. The in vitro cytotoxicity on Vero cells (CC50), as well as the selectivity index (SI = CC50/MIC) were also evaluated, and showed that the synthesized analogues are not cytotoxic.
  • New Epimeric Spirostanol and Furostanol-Type Steroidal Saponins from Cestrum laevigatum L. Articles

    Ribeiro, Paulo R. V.; Braz-Filho, Raimundo; Araújo, Ana J.; Costa-Lotufo, Letícia V.; Souza, Luciana G. S.; Nobre Junior, Hélio V.; Silva, Cecília R. da; Andrade Neto, João B. de; Silveira, Edilberto R.; Lima, Mary Anne S.

    Resumo em Inglês:

    Four new epimeric spirostanol and furostanol-type steroidal saponins, (25R,S)-5α-spirostan-2α,3β-diol 3-O-β-D-glucopyranosyl-(1→4)-β-D-galactopyranosyl-(1→4)-β-D-galactopyranoside, (25R,S)-5α-spirostan-2α,3β-diol 3-O-β-D-glucopyranosyl-(1→2)-α-L-rhamnopyranosyl-(1→4)-β-D-galactopyranoside, 26-O-β-D-glucopyranosyl-(25R,S)-5α-furost-20-ene,2α,3β-diol 3-O-β-D-galactopyranoside and 26-O-β-D-glucopyranosyl-(25R,S)-5α-furost-20-ene,2α,3β-diol 3-O-β-D-galactopyranosyl-(1→4)-β-D-galactopyranoside, in addition to the known (25R,S)-5α-spirostan-2α,3β-diol 3-O-β-D-galactopyranoside, were isolated from Cestrum laevigatum. Compounds were submitted to cytotoxic activity assays using colorectal adenocarcinoma (HCT-116), human promyelocytic leukemia (HL-60), ovarian carcinoma (OVCAR-8), glioma (SF-295) human cancer cell lines, and the antimicrobial activity was evaluated against Candida parapsilosis, C. albicans, C. krusei, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis.
  • Poly(dimethylsiloxane) and Poly[vinyltrimethoxysilane-co-2-(dimethylamino)ethyl methacrylate] Based Cross-Linked Organic-Inorganic Hybrid Adsorbent for Copper(II) Removal from Aqueous Solutions Articles

    Silva, Fábio A. B.; Chagas-Silva, Fátima A.; Florenzano, Fábio H.; Pissetti, Fábio L.

    Resumo em Inglês:

    An organic-inorganic hybrid adsorbent was prepared and its application for the uptake of CuII ions from aqueous solutions was studied. The polymer network was composed of poly(dimethylsiloxane) (PDMS), vinyltrimethoxysilane (VTMS), and 2-(dimethylamino)ethyl methacrylate (DMAEMA), described as PDMS-net-P(VTMS-co-DMAEMA). The chemical groups, thermal stability and morphology of this hybrid adsorbent were characterized using techniques of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). In adsorption studies, saturation of the active sites of the material was observed at pH 5, after 3 days, with each gram of material capable of adsorbing 0.48 mmol of copper(II). The fractionary-order and Sips models provided the best fits to the experimental data in kinetic and equilibrium studies of the adsorption process, respectively. Moreover, an acceptable reusability was found for this cross-linked organic-inorganic hybrid adsorbent after usage-regeneration cycles without significantly losing its original activity.
  • Emissions of Criteria and Non-Criteria Pollutants by a Flex-Fuel Motorcycle Articles

    Daemme, Luiz C.; Penteado, Renato; Corrêa, Sergio M.; Zotin, Fátima; Errera, Marcelo R.

    Resumo em Inglês:

    While criteria pollutants have established emission limits for motorcycles in Brazil, aldehydes limits have not been established and conclusive studies have not been found in the existing literature, despite the growing number of motorcycles using flex fuel in Brazil. This work presents results for the emissions of criteria pollutants, such as carbon monoxide, hydrocarbons and nitrogen oxides, acetaldehyde and formaldehyde. The motorcycle was tested with 22, 61, and 100% of ethanol in gasoline blends. Fourier transform infrared (FTIR) and high performance liquid chromatography (HPLC) were used to determine the pre- and post-catalytic converter emissions. Aldehyde emissions directly increased with the ethanol content in the fuel blend. The tailpipe aldehyde emissions for 22, 61, and 100% of ethanol in gasoline were 3.9, 8.5, and 38.8 mg km-1, respectively. These results demonstrated that aldehyde emissions in motorcycles are not negligible, and higher emissions are observed during the cold phase of the engine.
  • Bioactive Indole Alkaloids from Croton echioides Articles

    Novello, Claudio R.; Marques, Luís C.; Pires, Murilo E.; Kutschenco, Ana P.; Nakamura, Celso V.; Nocchi, Samara; Sarragiotto, Maria H.; Mello, João C. P.

    Resumo em Inglês:

    Bioguided fractionation of a hydroethanolic extract from the stem bark of Croton echioides Baill. led to isolation of the new indole alkaloid N-trans-feruloyl-3,5-dihydroxyindolin-2-one as a stereoisomeric mixture and the known alkaloids N-trans-p-coumaroyl-tryptamine, N-trans-p-coumaroyl-5-hydroxytryptamine, N-trans-4-methoxy-cinnamoyl-5-hydroxytryptamine, N-trans-feruloyl-5-hydroxytryptamine (moschamine), from the ethyl acetate fraction. The flavonoids 3-o-methyl kaempferol, 3-o-methyl quercetin, 3,7-di-o-methyl quercetin and 3,3'-di-o-methyl quercetin, together with the benzoic acid derivatives 4-hydroxybenzoic acid, 4-hydroxy-3-methoxybenzoic acid and 4-hydroxy-3,5-dimethoxybenzoic acid were also isolated. Alkaloids and the flavonoids showed strong antioxidant properties in vitro radical scavenging assay (2,2-diphenyl-1-picrylhydrazyl, DPPH), with IC50 values ranging from 9.2 to 17.5 µmol L-1, lower than those of the positive control Trolox (IC50 = 17.9 µmol L-1). Alkaloids showed cytotoxic activity against the HCT-116 human cancer cell line, with IC50 values ranging from 86.8 to 210.7 µmol L-1. Compound N-trans-4-methoxy-cinnamoyl-5-hydroxytryptamine was the most active, with an IC50 value of 86.8 µmol L-1.
  • The Effect of Atmosphere on Elemental Mercury Release During Thermal Treatment of Two Bituminous Coals Articles

    Gao, Libing; Guo, Shaoqing; Wei, Xian-Xian; Cao, Yanzhi

    Resumo em Inglês:

    The dynamic release behavior of elemental Hg (Hg0) during thermal treatment of two bituminous coals was studied under N2, CO2 and air atmospheres. The results show that the profiles of Hg0 released present several peaks during thermal treatment of two bituminous coals. The Hg peak profiles for the same coal are different with the different atmosphere used. The amount of Hg0 released from the coals is about 92-94, 73-74 and 31-33% under N2, CO2 and air atmosphere, respectively. This indicates that the Hg0 is the dominant form during thermal treatment of the coals under N2 atmosphere whereas part of Hg0 is converted into the oxidized Hg during thermal treatment of the coals under CO2 and air atmosphere. The total Hg released is promoted by the volatile matter release to some extent while the Hg0 released is mainly affected by the atmospheres used.
  • Voltammetric Determination of Sulfonamides with a Modified Glassy Carbon Electrode Using Carboxyl Multiwalled Carbon Nanotubes Articles

    He, Bao-shan; Chen, Wen-bo

    Resumo em Inglês:

    New glassy carbon electrode (GCE) modified with carboxyl multiwalled carbon nanotubes (MWCNTs) and treated with ultrasonic dispersing in N,N-dimethylfomamide (DMF) media, namely DMF/carboxyl/MWCNTs/GCE, was prepared for electrochemical determination of sulfonamides (SAs). Electrochemical behavior of SAs based on DMF/carboxyl/MWCNTs/GCE was investigated by cyclic voltammetry and impedance spectroscopy. The effects of various experimental parameters on the response of electrode such as pH of buffer, scan rate and the amount of modification were optimized. Under the optimal conditions, the obtained sensor presented linear response to SAs in the range of 5.0 × 10-7 to 1.1 × 10-4 mol L-1 of sulfonamide (R = 0.999), sulfamethazine (R = 0.990), sulfadiazine (R = 0.997), sulfamethoxazole (R = 0.996) and the limits of detection of 1.65 × 10-8, 3.19 × 10-8, 6.76 × 10-8 and 9.41 × 10-8 mol L-1, respectively. The recoveries were in the range of ca. 85-103% with relative standard deviation (RSD) < 5%. The sensor was tested by cyclic voltammetry with repeatability and stability of more than 90% of its original activity. The proposed method might offer feasibility and applicability of the sensor for further complex sulfonamides compounds.
  • The Influence of Organic Medium and Supports in the Resolution of (R,S)-Menthol Catalyzed by Lipases Articles

    Silva, Julyetty Crystyne da; Nascimento, Maria da Graça

    Resumo em Inglês:

    In this study, various commercial and native lipases, free or immobilized, were used in the enantioselective resolution of (R,S)-menthol with vinyl acetate for the preparation of menthyl acetate. Lipase from Candida rugosa (AYL) was found to be the most appropriate. When the reaction was carried out at 35 ºC, using 40 mg of AYL and a molar ratio of 1:2 (alcohol:ester), the values for the conversion degree, the enantiomeric excess of the substrate (ees) and product (eep) and the enantiomeric ratio (E) were 33.6, 50.3, > 99% and > 200, respectively. The results showed that the reaction was more efficient using toluene in comparison with other organic solvents or mixtures of toluene and ionic liquids (ILs). The best support for the AYL immobilization, was corn starch film. This system was used 4 times over 71 days of storage, and menthyl acetate was still obtained with good values of conversion degree, ees, eep, and E.
  • Assessment of Trace Elements in Tissues of Fish Species: Multivariate Study and Safety Evaluation Articles

    Silva, Edevaldo; Costa, Fernanda N.; Souza, Thais L.; Viana, Zenira C. V.; Souza, Anderson S.; Korn, Maria G. A.; Ferreira, Sergio L. C.

    Resumo em Inglês:

    Levels of As, Cd, Cr, Cu, Li, Mn, Mo, Ni, Pb, Sb and Se in muscle, gill, stomach, liver, kidney and gonad tissues of six different fish species (Caranx latus, Bagre marinus, Archosargus rhomboidalis, Lutjanus synagris, Scomberomorus cavalla and Sphyraena guachancho) from the Todos os Santos Bay (Bahia State, Brazil) were evaluated. The elements were determined by inductively coupled plasma mass spectrometry (ICP-MS) after wet digestion using reflux system with a cold finger. The detected concentration ranges were as follows (mg kg-1 dry weight): < 0.49-27.31 for As, < 0.013-1.12 for Cd, 0.38-6.05 for Cr, 0.17-28.12 for Cu, < 0.092-1.19 for Li, 0.16-55.9 for Mn, < 0.034-1.24 for Mo, < 0.067-15.57 for Ni, < 0.013-0.60 for Pb, < 0.144 for Sb and 0.57-14.6 for Se. Highest concentrations of trace elements were observed in kidney, liver and gill tissues.
  • Grinding and Milling: Two Efficient Methodologies in the Solvent-Free Phosphomolybdic Acid-Catalyzed and Mechanochemical Synthesis of cis-4-Amido-N-yl-2-methyl-tetrahydroquinolines Articles

    Kouznetsov, Vladimir V.; Merchán-Arenas, Diego R.; Martínez-Bonilla, Carlos A.; Macías, Mario A.; Roussel, Pascal; Gauthier, Gilles H.

    Resumo em Inglês:

    The ball-milling process of ABB' Povarov reaction through mechano-chemical activation with phosphomolybdic acid (PMA) as heteropolyacid (HPA) catalyst, was first time explored. The developed high speed vibratory ball milling (HSVBM) green method offers simple and efficient diastereoselective synthesis of cis-2,4-disubstituted tetrahydroquinolines in good to excellent yields (56-76%).
  • Photocatalytic Degradation for Treating Multipesticide Residues Using [Ru(bipy)3]Cl2-Doped TiO2/SiO2 Based on Surface Response Methodology Articles

    Guimarães, Bruno de S.; Bernardes, Arthur A.; Salcedo, Gabriela M.; Caldas, Sergiane S.; Jorge, Marianna B.; Bianchini, Adalto; Wolke, Silvana I.; Primel, Ednei G.

    Resumo em Inglês:

    This study aimed to develop and optimize an efficient photocatalytic process employing ruthenium [Ru(bipy)3]2+ doped TiO2-SiO2 for degrading synthetic wastewater containing six classes of pesticides (bentazone, carbofuran, clomazone, diuron, tebuconazole and pyraclostrobin). To optimize the degradation conditions for the six pesticides and assess the effect of two variables (reaction time and adsorption equilibrium time) on the heterogeneous photocatalytic process, a 22 experimental design with a central composite rotatable design (CCRD) was used. The CCRD was suitable for optimizing the heterogeneous photocatalysis, and the generated surface responses indicated that the best removal conditions were 15 min adsorption equilibrium time and 110 min reaction time. Under these conditions, a pesticide removal between 71.00 and 99.98% was obtained. Furthermore, the system yielded an excellent degree of synthetic wastewater mineralization, with 97.60% total organic carbon (TOC) removal after 110 min.
  • Treatment of Sanitary Landfill Leachate by Photo-Fenton Process: Effect of the Matrix Composition Articles

    Silva, Jader O.; Silva, Valdislaine M.; Cardoso, Vicelma L.; Machado, Antonio E. H.; Trovó, Alam G.

    Resumo em Inglês:

    In this study it was evaluated the role of the composition of sanitary landfill leachate on the removal of dissolved organic carbon (DOC) by photo-Fenton process. The composition of the matrix (high turbidity and color, as well as presence of inorganic ions sulfate and chloride) does not reduce the efficiency of DOC removal by photo-Fenton reactions, but influences significantly the reaction time and consumption of H2O2. An expressive increase in the efficiency of DOC removal occurred for concentrations of Fe2+ between 50 and 100 mg L-1, remaining constant in the range between 100 and 200 mg L-1. On the other hand, the pre-treatment of this effluent by coagulation-flocculation before the photo-Fenton process is recommended, since a similar efficiency of DOC removal, between 70 and 77%, was achieved using only 17% of the time and 7% of H2O2 necessary for the treatment of raw leachate treatment.
  • Evaluation of Major and Trace Elements in Medicinal Plants Articles

    Silva, Paulo S. C.; Francisconi, Lucilaine S.; Gonçalves, Rodolfo D. M. R.

    Resumo em Inglês:

    This study presents the elemental concentration results obtained from 59 medicinal plants used in Brazil, determined by instrumental neutron activation analysis (INAA), inductively coupled plasma-optical emission spectrometry (ICP OES) and cold vapor atomic absorption spectrometry (CV AAS). The selected plant species were chosen from the Brazilian National Agency for Sanitary Vigilance (ANVISA) list of herbs recommended for utilization by the Public System of Health in Brazil (SUS). The results showed that high levels of foreign matter were found in almost 50% of the analyzed samples. The concentration of the elements varied in a wide range, although, generally in accordance with values found in literature. High concentrations of Ba, Cr, Fe, Hg, Se and Ni were found in some samples. The enrichment factor indicated that potentially hazardous elements can be accumulated mainly in the bark of the plants, possibly indicating an anthropogenic contribution.
  • A Mesoporous SiO2/γ-Fe2O3/KI Heterogeneous Magnetic Catalyst for the Green Synthesis of Biodiesel Articles

    Macedo, Alice L.; Fabris, José D.; Pires, Manoel J. M.; Oliveira, Wanessa L.; Ardisson, José D.; Augusti, Rodinei; Aragón, Fermin H.; Santos, Ricardo S.; Oliveira, Luiz C. A.; Pereira, Márcio C.

    Resumo em Inglês:

    A magnetic catalyst (sample MCat) consisting of KI supported on a mixture of silica and maghemite (γ-Fe2O3) was prepared and used in the transesterification reaction for the synthesis of biodiesel. The energy dispersive X-ray spectrum of the catalyst showed signals due to Si, Fe, K, and I. Powder X-ray diffraction data revealed the amorphous nature of the SiO2 and the duly impregnation of the support with KI. 57Fe Mössbauer spectroscopy and magnetization measurements confirmed the ferrimagnetic iron oxide in the catalyst to be maghemite. N2 adsorption-desorption data indicated that the silica is mesoporous with a specific area of 352 m2 g-1, enabling the impregnation of 40 and 11 wt.% of KI and maghemite, respectively, according to the chemical composition obtained by the X-ray fluorescence measurements. The MCat was found to be efficient in the transesterification reaction in the macaúba and soybean oils. The MCat was easily removed from the reaction medium, with a hand magnet, and efficiently reused for more four consecutive reaction cycles. The good catalytic activity along with its magnetic behavior, high chemical stability and recyclability make the MCat a suitable material for the green synthesis of biodiesel.
  • Design of a New Molecularly Imprinted Polymer Selective for Hydrochlorothiazide Based on Theoretical Predictions Using Gibbs Free Energy Articles

    Barros, Leonardo A.; Custodio, Rogério; Rath, Susanne

    Resumo em Inglês:

    A molecularly imprinted polymer (MIP) for the diuretic drug hydrochlorothiazide (HCTZ) based on theoretical predictions was developed. Molecular modeling calculations were performed to study the intermolecular interactions in the pre-polymerization mixture and to select a suitable functional monomer and a porogenic solvent for the synthesis of the MIP. To confirm the results of the theoretical predictions, three MIPs were synthesized and evaluated using the equilibrium batch rebinding method. A water-compatible MIP was prepared using HCTZ as the template and acrylamide as the functional monomer (FM) with ethylene glycol dimethacrylate as the cross-linker and tetrahydrofuran as the porogen. An imprinting factor of 8.24 was obtained. The polymer was characterized by Fourier transform infrared (FTIR), solid-state nuclear magnetic resonance, scanning electron microscopy, thermogravimetric analysis and nitrogen sorption porosimetry. In addition to HCTZ, six structurally related compounds were tested to evaluate the selectivity of the HCTZ-MIP, and cross-selectivity of the MIP was verified.
  • Fragmental Method KowWIN as the Powerful Tool for Prediction of Chromatographic Behavior of Novel Bioactive Urea Derivatives Articles

    Flieger, Jolanta; Tatarczak-Michalewska, Małgorzata; Kowalska, Anna; Rządkowska, Marzena; Szacoń, Elżbieta; Kaczor, Agnieszka A.; Matosiuk, Dariusz

    Resumo em Inglês:

    A series of the new urea derivatives with antinociceptive activity has been chromatographically evaluated using reversed phase materials: Zorbax Extend-C18, Cogent UDC Cholesterol with organic-aqueous eluent systems with two organic modifiers (methanol and acetonitrile). The chromatographic lipophilicity parameters: log kw, S and φ0 were determined basing on linear relationship between log k values and concentration of organic mobile phase modifier. The structure-retention studies revealed that the retention mechanism for all studied urea derivatives is uniform for the proposed chromatographic systems. However, a few exceptions were noticed. Derivatives containing nonpolar substituents in the imidazole ring acted as outliers for cholesterol column. In turn, the derivative containing ester polar substituent acted as an outlier in conventional reversed-phase system. Quantitative relationships based on a wide set of established computational molecular descriptors and experimental chromatographic data were also developed. Through a systematic study, by using the principal component analysis, fragmental method KowWIN appeared to be the most powerful software to produce reliable estimations of experimental retention parameters obtained on cholesterol column.
  • Crystal Structures of 1-Aryl-1H- and 2-Aryl-2H-1,2,3-triazolyl Hydrazones. Conformational Consequences of Different Classical Hydrogen Bonds Articles

    Gonzaga, Daniel T. G.; Silva, Fernando C. da; Ferreira, Vitor F.; Wardell, James L.; Wardell, Solange M. S. V.

    Resumo em Inglês:

    The crystal structures of (Z)-1-phenyl-4-[((2-phenylhydrazono)methyl)]-1H-1,2,3-triazole, (Z)-4-[(2-(2,4-dimethylphenyl)hydrazono)methyl]-2-phenyl-2H-1,2,3-triazole, (E)-4-[(2-(2,4-dinitrophenyl)hydrazono)methyl]-2-phenyl-2H-1,2,3-triazole, and (E)-N'-((2-phenyl-2H-1,2,3-triazol-4-yl)methylene)isonicotinohydrazide dihydrate are reported. The formations of (Z)- configurations about the C=N bonds in the first two compounds arise from the stabilizing presence of intramolecular N-H···N hydrogen bonds, while in the third compound, the presence of intramolecular N-H···O hydrogen bonds promotes an (E) geometry. The arrangement about the CONHC=N fragment in the hydrated acylhydrazone is EC(O)NH/EC=N. Also present in (E)-N'-((2-phenyl-2H-1,2,3-triazol-4-yl)methylene)isonicotinohydrazide is an interesting R44(8) ring formed from hydrogen bonds generated from four water molecules. Significant π···π stacking interactions are exhibited in three compounds, but not in the least planar first compound, in which the dominant intermolecular interactions are C-H···π interactions. Other intermolecular interactions in one of the compounds are C-H···π interactions, in another compound are C-H···O hydrogen bonds and N-O···π interactions, and in the last compound are O-H···X (X = O and N), N-H···O and C-H···O hydrogen bonds.
  • Metal Complex Derivatives of Azole: a Study on Their Synthesis, Characterization, and Antibacterial and Antifungal Activities Articles

    Castillo, Keshia F.; Bello-Vieda, Nestor J.; Nuñez-Dallos, Nelson G.; Pastrana, Homero F.; Celis, Adriana M.; Restrepo, Silvia; Hurtado, John J.; Ávila, Alba G.

    Resumo em Inglês:

    Four new zinc complex derivatives of azoles and ligands were synthesized and isolated as white air-stable solids and characterized by elemental analyses, thermogravimetric analysis (TGA), infrared spectroscopy, nuclear magnetic resonance (NMR) and mass spectra. The elemental analysis, theoretical calculations and NMR show that the complexes likely have a 1:1 (M:L) stoichiometry and tetrahedral geometry. To evaluate the biological activity of the complexes and to discuss the role of metal ions and structural properties, the ligands and their metal complexes have been studied. Their antimicrobial activity was determined in vitro by agar-well diffusion and broth microdilution against nine bacterial strains and seven fungal strains with clinical relevance. In vitro assays showed that the complexes exhibited moderate antibacterial and/or antifungal activities. The antimicrobial activity was found to be more active for the metal complexes than the ligands. The metal complexes that contained copper and cobalt, respectively, displayed notable antibacterial and antifungal effects against all the tested bacterial strains. The minimum inhibitory concentration 50 (MIC50) values were in the range 2454-0.7 µg mL-1. Metal complexes were more effective at inhibiting bacteria than fungi. The results could provide a high-potential solution for antimicrobial growth resistance, for both bacteria and fungi.
  • Simultaneous Determination of Rare Earth Elements by ICP OES After On-Line Enrichment Using Multi-Walled Carbon Nanotubes Coated Cellulose Acetate Membrane Articles

    Zolfonoun, Ehsan; Yousefi, Seyed Reza

    Resumo em Inglês:

    This study investigates application of multi-walled carbon nanotubes coated cellulose acetate membrane for on-line extraction and preconcentration of some rare earth elements (Y, La, Ce, Nd, Sm, Gd and Dy) prior to their determination by inductively coupled plasma optical emission spectrometry. Sample solutions containing rare earth elements (pH: 6.0) and l-(2-pyridylazo) 2-naphtol (4.0 × 10-5 mol L-1) were passed through the membrane (flow rate: 5.0 mL min-1). The adsorbed cations were subsequently eluted from the membrane and transferred into the plasma with nitric acid solution (flow rate: 3.0 mL min-1) for simultaneous determination of them. The effect of different experimental parameters on the performance of the method were studied and discussed. Under the optimized conditions and preconcentration of 25 mL of sample, the enrichment factors of 185-201 and the detection limits of 0.05-0.3 µg L-1 were obtained.
  • Catalytic Capture of CO2 with Template-Containing Zn/MCM-41 and Its Transformation to Solid Carbonate Articles

    Pirouzmand, Mahtab; Nikzad-Kojanag, Behnaz; Hosseini-Yazdi, Seyed Abolfazl

    Resumo em Inglês:

    Mesoporous MCM-41 materials modified by zinc have been prepared by non hydrothermal procedure. Zinc has been introduced by the direct synthesis (DS), template ion-exchange (TIE) and wet impregnation (WI) methods. The catalysts were characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy-scanning electron microscopy (EDX-SEM), thermogravimetric and differential thermal analyses (TGA-DTA), Fourier transform infrared spectroscopy (FTIR) and N2 adsorption/desorption measurements. The obtained catalysts were investigated for hydration of CO2 and its precipitation as CaCO3 at room temperature. We investigated the effect of synthesis method and cationic template on catalytic activity of Zn/MCM-41 catalysts. The results showed that template containing Zn/MCM-41 prepared by template ion exchange technique has high CO2 hydration activity. This high activity is due to the presence of strong basic sites. It was also found that this catalyst can be easily recovered from the reaction mixture and reused without activation.
  • Gas-Phase Conversion of Glycerol to Acetol: Influence of Support Acidity on the Catalytic Stability and Copper Surface Properties on the Activity Articles

    Braga, Tiago Pinheiro; Essayem, Nadine; Prakash, Swamy; Valentini, Antoninho

    Resumo em Inglês:

    Mesoporous mixed copper-aluminum oxides and copper-silicon oxides were synthesized with polymeric precursors route in order to evaluate the effect of the support acidity on the catalytic stability due to the carbon deposit and the copper surface characteristics on the catalytic activity for the gas-phase conversion of glycerol to acetol. The samples were characterized by different techniques such as inductively coupled plasma (ICP), thermogravimetry and differential thermal analyses (TGA-DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption/desorption isotherms, temperature-programmed reduction with H2 (H2-TPR) and microcalorimetry of NH3 adsorption. The metallic copper surface was shown by XPS, which was observed an increase with the copper loading without marked changes between Si or Al support using the same copper content. The Cu-Al catalysts present acidic properties close to that of the pure alumina support while the Cu-Si solid is not acid, as expected. Reduced catalysts were evaluated in the reaction of glycerol conversion. The catalytic results showed a clear dependence of the glycerol conversion to acetol with the Cu metal surface and the initial catalytic properties did not depend on the support acidity, since the copper is the major active site. It was observed 95% of acetol selectivity and 80% of glycerol conversion for the best catalyst. However, the support acidity influenced the catalyst stability, since Cu-Al solid deactivated continuously by contrast to Cu-Si sample, which reached stability after 2 h of reaction. The higher acidity for the Al support leads to a greater carbon deposit compared to Si support, blocking the active sites and providing a rapid catalytic deactivation.
  • Principal Component Analysis of Commercial Tannin Extracts Using Digital Images on Mobile Devices Articles

    Grasel, Fábio S.; Ferrão, Marco F.; Helfer, Gilson A.; Costa, Adilson B.

    Resumo em Inglês:

    Tannins from trees are an abundant renewable resource. The use of tannins is safe for the environment and human health, making it possible to develop environmentally friendly products, such as adhesives, flocculant agents for water treatment, flame retardant foams and anticorrosives. In this study, a methodology was developed for the identification of six commercial tannin extracts (chestnut, valonea, tara, myrobalan, quebracho and black wattle) using digital images on mobile devices. The identification of the extracts was based on principal component analysis using the PhotoMetrix® mobile application. In the evaluation of the principal components, it was possible to define the separation between the six classes of extracts by color evaluation, according to the extract origin. In the analysis of PC1 × PC2, black wattle was very close to quebracho and chestnut was close to valonea; these extracts are chemically similar. The methodology developed for the analysis of tannin extracts obeys the principles of green chemistry requiring no reagents, and is fast, non-destructive and inexpensive.
  • Ultrasound-Assisted Synthesis of Isatin-Type 5'-(4-Alkyl/Aryl-1H-1,2,3-triazoles) via 1,3-Dipolar Cycloaddition Reactions Short Reports

    Silva, Bianca N. M.; Pinto, Angelo C.; Silva, Fernando C.; Ferreira, Vitor F.; Silva, Bárbara V.

    Resumo em Inglês:

    This short report describes the preparation of twelve isatin derivatives, 5'-(4-alkyl/aryl-1H-1,2,3-triazoles), using 5-azido-spiro[1,3-dioxolane-2,3'-indol]-2'(1'H)-one in the presence of various alkynes under acidic conditions and ultrasound irradiation. Compared with conventional methods, yields increased to 78-98%, and reaction times decreased to 5 min. Besides time and energy saving, there was no need for purification of the product by column chromatography on silica gel, generating less waste and spent solvent.
  • Alternative Model for RND-Type Efflux Pump Short Reports

    Torres, Pedro Henrique Monteiro; Pascutti, Pedro Geraldo; Bisch, Paulo Mascarello; Silva, Manuela Leal da

    Resumo em Inglês:

    RND (resistance-nodulation-division) transporters are found in several Gram-negative bacteria species. These proteins form a complex along with membrane fusion proteins and outer membrane factors. This complex acts as an efflux pump, transporting several different molecules directly from the cytoplasm to the extracellular medium. Although the crystallographic structure of each protein of the complex is known, the complete complex assembly is not yet fully characterized. In 2014, a model for the complete system, based upon a cryoelectron-microscopy map, was proposed. In the present work, we propose an alternative model that also satisfies the volume obtained from the cryoelectron-microscopy assay. In this model, the AcrA helical domains are interleaved to the helical domains of the TolC protein, increasing the diameter of the formed pore. We believe that this model represents a better model for RND-type efflux pump and might contribute to the characterization of this system.
  • A One-Pot Domino Synthesis of 4-(Trifluoromethyl)-2-thiazolamine Short Report

    Bao, Xue-fei; Qiao, Xue-jun; Hou, Xiao; Fang, Wu-hong; Liu, Xue-long; Chen, Guo-liang

    Resumo em Inglês:

    Triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) is commonly used as an antibacterial agent in various industrial products and is often detected in wastewater effluent. Comparison was made for triclosan degradation by photolysis and TiO2 photocatalysis (under UV irradiation (125 W)) based on analysis of transformation products, together with ecotoxicity evaluation. The morphology of the TiO2 was characterized by X-ray diffractometry (XRD) and field emission gun-scanning electron microscopy (FEG-SEM). Triclosan quantitation was performed by high performance liquid chromatography (HPLC). The optimal condition was obtained using a response surface model and desirability profile. The initial concentration of triclosan used in all the experiments was 10 mg L-1 to achieve comprehensive identification of transformation products. The optimal experimental condition was 30 mg L-1 TiO2 at pH 10. The photocatalytic system achieved > 99% triclosan degradation at 30 min of reaction. The mineralization rates by photolysis and photocatalysis were 25 and 90%, respectively. A total of 27 transformation products were identified using liquid chromatography quadrupole time of flight mass spectrometry (QTOF MS), being that 25 were new structures, not previously reported in the literature. Ecotoxicity assays demonstrated that triclosan and some of the major transformation products did not cause deleterious effects towards Lactuca sativa and Daphnia magna after 16 h of treatment.
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