Scielo RSS <![CDATA[Journal of the Brazilian Chemical Society]]> vol. 28 num. 2 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Microwave Assisted Synthesis of Novel Six-Membered 4-C, 4-O and 4-S Lactams Derivatives: Characterization and <em>in vitro</em> Biological Evaluation of Cytotoxicity and Anticoagulant Activity]]> A series of six-membered lactam derivatives containing C, O and S atoms in position 4 were synthesized using microwave methodology through coupling reactions. The novel compounds were synthesized following two step reaction to yield fifteen derivatives. The final derivative N-(4-(3-oxotiomorpholin)phenyl) hexanamide was selectively toxic to the HCT-116 cell line over the HeLa cancerous and HEK-293 human non-malignant control cells with low inhibition Factor Xa (FXa) activity. The new products were characterized by spectral data including 1H and 13C nuclear magnetic resonance (NMR), infrared (IR) and high-resolution mass spectrometry (HRMS). Cytotoxicity of products on HCT-116, HeLa, HEK-293 cell lines and FXa activity assays are also reported. <![CDATA[Smectite Clay Modified with Quaternary Ammonium as Oil Remover]]> Clays such as smectite have high technical and economic viability due to their large adsorption capacity. These properties can be improved by treatment with acids or other modifications. This paper describes experiments to prepare and characterize organoclays and to evaluate their ability to remove oil from contaminated water in comparison with clay in its natural state. We used natural smectite clay from the municipality of Presidente Dutra, Maranhão State, modified with the quaternary ammonium salt cetyltrimethylammonium bromide. Characterization was performed by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray fluorescence, thermogravimetry and determination of surface area by the Brunauer-Emmett-Teller (BET) method. The results showed appropriate conditions of the organophilization process, indicating the intercalation of quaternary ammonium cations between the clay layers. The adsorption tests showed that the natural clay reduced the amount of oil contained in the aqueous medium by 76.16%, while the corresponding removal rates of all organoclays tested were above 92%, which makes them potentially applicable to remove oil from wastewaters. <![CDATA[Ultrasound-Promoted Synthesis of 3-(Thiophen-2-yl)-4,5-dihydro-1<em>H</em>-pyrazole-1-carboximidamides and Anticancer Activity Evaluation in Leukemia Cell Lines]]> 3-(Thiophen-2-yl)-4,5-dihydro-1H-pyrazole-1-carboximidamides were efficiently prepared through a cyclocondensation of thiophenylchalcones with aminoguanidine hydrochloride under ultrasonic conditions in the presence of KOH and ethanol as a green solvent in short reaction times (15-35 min) and good yields (62-95%). All compounds produced were evaluated against the human Jurkat and RS4;11 acute lymphoblastic leukemia cell lines of T- and B-cell origin, respectively, and the K562 myelogenous leukemia cell line. Six compounds presented half maximal inhibitory concentration (IC50) values around 15 µmol L-1 and five compounds presented IC50 values around 40 µmol L-1 for at least one of the three cell lines analyzed. One compound was not significantly cytotoxic, presenting IC50 value &gt; 100 µmol L-1. <![CDATA[Ion Exchange Chromatography and Mass Bias Correction for Accurate and Precise Zn Isotope Ratio Measurements in Environmental Reference Materials by MC-ICP-MS]]> Precise and accurate d66/64Zn data for environmental reference materials (RMs) including rocks, sediments, soils and plants are presented in order to improve the metrological traceability and analytical control of Zn isotope ratio determinations in future environmental studies. Previously developed ion exchange chromatography protocols were adjusted to enable faster sample throughput and instrumental mass bias processes were investigated. The improved chromatographic protocol yielded precise and quantitative recoveries (99 ± 7%, σ, n = 16), while the mass bias correction using Cu as external dopant provided precisions better than 0.02‰, 2σ, n = 7. Investigations into spectral and non-spectral interferences identified significant formation of Cr and Ti oxides and hydroxide ionic species. Analysis of six RMs (BHVO-2 basalt (USGS), BCR-2 basalt (USGS), AGV-2 andesite (USGS), 2709 San Joaquin soil (NIST), 1646a estuarine sediment (NIST) and 1573a tomato leaves (NIST)) showed good reproducibility (&lt; 0.01‰, 2s, 5 ≤ n ≥ 1). <![CDATA[Validation of a Chromatographic Analytical Method for Quantification of Benznidazole Incorporated in Nanostructured Lipid Formulations]]> Benznidazole (BNZ) has been employed in the treatment of Chagas disease; however, its low water solubility is a drawback, which can be overcome by incorporating BZN within nanostructured systems. The aim of this work was to validate a chromatographic method for determination of BZN incorporated in nanoemulsions (NE) and nanostructured lipid carriers (NLC). The method was validated according to the International Conference on Harmonization guidelines. No interferences from the excipients of both systems on the BZN peak were observed. Linearity presented a correlation coefficient higher than 0.99 in the range of 5.0-30.0 µg mL-1. Relative standard deviation values for intra- and inter-days precision were lower than 2% and mean recovery ranged from 93.6 to 105.7%. BZN-loaded nanocarriers exhibited physico-chemical characteristics acceptable for parenteral administration and the encapsulation efficiency was almost 100% for both systems. The method shows a good potential to be employed in the determination of BZN in lipid nanostructures. <![CDATA[Structural Analysis of High-Spin States of S0-S4 at OEC Complex: A Theoretical Approach of Small Models]]> S-states at oxygen evolving complex (OEC) are widely studied due to its large importance in photo-oxidation water process. The structural aspects involving S0, S1, S2, S3 and S4 states are still not solved theoretically. Particularly, spin states have been analyzed as an important aspect in S-state models. Seeking to obtain a relevant and simple model to cover high-spin (HS) S0-S4 states we develop a 55-57 atoms model. Through quantum chemical calculations we figured out that our interatomic distance parameters are in agreement with experimental and other theoretical reference values by ca. 10.0 and 3.5%, respectively, being also in good agreement with other theoretical models containing a large number of atoms. Our HS models presented expected oxidation states according to other data on literature for small theoretical models. <![CDATA[Determination of Moxidectin in Serum by Liquid Chromatography-Tandem Mass Spectrometry and Its Application in Pharmacokinetic Study in Lambs]]> The widespread use of moxidectin (MOX), a parasiticide used in the sheep breeding, has induced the parasite resistance in Brazilian farms. As a consequence, the farmers often increase the dose and frequency of drug utilization, and disregards safety of meat or milk. In order to establish adequate therapeutic treatment it is necessary to know the pharmacokinetics of the drug in the animal's body. Thus, high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) method was developed for the determination of MOX in serum lamb. Serum samples were treated with acetonitrile to precipitate proteins. A clean up by dispersive extraction in solid phase (SPE-d), using primary/secondary amine (PSA) and C18 sorbents, followed by freezing was performed. Method validation presented precision (coefficient of variation) and accuracy (recovery%) between 1.7-6.7 and 80.0-107.3%, respectively. The limit of quantification (LOQ) of the method was 2.0 ng mL-1 and a linear response was obtained over a range of 2.0 to 100 ng mL-1. This method was successfully applied to the determination of MOX in serum from suffolk lamb to evaluate the pharmacokinetic profile. <![CDATA[Development of Molecularly Imprinted Polymers for Solid Phase Extraction of Parabens in Plasma Samples and Analysis by UHPLC-MS/MS]]> Two molecularly imprinted polymers (MIPs) were synthesized, by sol-gel and radical polymerization procedures. These MIPs were evaluated as selective stationary phases for miniaturized solid phase extraction (MISPE) to determine parabens in plasma samples by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Selective cavities of the MIPs, based on molecular recognition (hydrogen bonds), were revealed after removal of the template (benzylparaben). Both MIPs were characterized by scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FTIR). MIP prepared by radical process presented higher selective binding capacity for the target parabens than MIP prepared by sol-gel. Several variables that influence MISPE performance, including sample pH, sorbent washing, elution solvent, and elution solvent volume were also evaluated. According to the analytical validation parameters, the MISPE/UHPLC-MS/MS method is suitable for the analysis of parabens in plasma samples. The effectiveness of this method was demonstrated through the analyses of the umbilical plasma samples from postpartum women. <![CDATA[Speciation of Chromium in Water Samples after Dispersive Liquid-Liquid Microextraction, and Detection by Means of High-Resolution Continuum Source Atomic Absorption Spectrometry]]> A newly analytical method has been developed to determine total chromium and speciation of this element in water samples through dispersive liquid-liquid microextraction combined with a high-resolution continuum source flame atomic absorption spectrometry. The most significant variables affecting complexation and extraction were optimized by using response surface methodology and univariate optimization. The best conditions for both the complexation and extraction elements in this study were: complexing agent ammonium pyrrolidine dithiocarbamate (APDC 6.0 mmol L-1); pH at 2.0 (CrVI) and at 7.0 (Cr total); NaCl (5% m/v); 1-undecanol (50 µL) and ethanol 300 (CrIV) and 275 µL (total Cr). Under optimal conditions, this method resulted in a 20-100 µg L-1 linear range for CrVI and total chromium, detection limits of 0.35 (CrVI) and 6.7 µg L-1 (total Cr), as well as enriching factor of 26 (CrVI) and 19 for total Cr. The method accuracy was carried out by using certified water reference material (NIST CRM 1643e), and the results achieved were in agreement with the certified value (t-test at a confidence interval of 95%). The method developed was applied in samples of mineral water, tap water (the recovery values ranged from 88 to 115%) and seawater. <![CDATA[Electrochemiluminescence Sensor for the Detection of Tiapride Hydrochloride with Chitosan-Ru(bpy)<sub>3</sub><sup>2+</sup>-SiO<sub>2</sub>NPs/MCNT/Nafion Modified Electrode]]> Chitosan-Ru2(bpy)32+-SiO2 composite nanoparticles (CRuS NPs) were prepared by reverse microemulsion method for the electronic attraction between negative charge of hydroxyl groups in chitosan and positive charge in Ru2(bpy)3 2+. Based on the multi-walled carbon nanotubes (MCNT)/Nafion composite membrane technology, CRuS NPs was effectively and steadily immobilized on the surface of a glassy carbon electrode. The CRuS NPs synthesized were characterized by transmission electron microscope (TEM), UV-Vis spectroscopy and fluorescence spectroscopy, while the modification was confirmed by cyclic voltammetry and electrogenerated chemiluminescence (ECL). The ECL studies revealed that the sensor had a good response to different concentrations of tiapride hydrochloride and the increased ECL intensity was directly related to the logarithm of tiapride hydrochloride concentrations in the range from 0.01 to 3.0 µmol L-1 with a detection limit of 6.0 nmol L-1. The sensor was successfully applied to the determination of tiapride hydrochloride in pharmaceutical. <![CDATA[New Multicomponent Reaction for the Direct Synthesis of β-Aryl-γ-nitroesters Promoted by Hydrotalcite-Derived Mixed Oxides as Heterogeneous Catalyst]]> A new approach based on multicomponent/domino combined reactions for the synthesis of γ-nitroesters promoted by a mixed aluminium-magnesium oxides derived from hydrotalcite-like material was developed. Different γ-nitroesters were synthesized in 15-95% yield using Meldrum's acid, aromatic aldehydes, nitromethane and different alcohols as reagents and solvents. The γ-aminobutyric acid derivatives, Phenibut and Baclofen, were prepared in 63 and 61% overall yield, respectively, through a two steps synthetic strategy. A mechanistic pathway was proposed based on the gas chromatography mass spectrometry (GC-MS) and electrospray ionization mass spectrometry (ESI-MS) experiments. <![CDATA[Graphene Oxide/Zinc Oxide (GO/ZnO) Nanocomposite as a Superior Photocatalyst for Degradation of Methylene Blue (MB)-Process Modeling by Response Surface Methodology (RSM)]]> The photocatalytic performance of graphene oxide/zinc oxide (GO/ZnO) nanocomposite was investigated for degradation of methylene blue (MB) from wastewater and was compared with that of zinc oxide (ZnO), graphene oxide (GO) and carbon nanotube/zinc oxide (CNT/ZnO). The properties of the GO/ZnO nanocomposite were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM and TEM results revealed the nanostructure of the composite. The photocatalytic process was modeled by response surface methodology (RSM), considering four independent factors. The significance of the model was approved by analysis of variance (ANOVA) (determination coefficient R2 = 0.95, R2adj = 0.91). The optimum conditions of the process were found to be at photocatalyst dosage, initial pH, H2O2 concentration and irradiation time of 2.1 g L-1, 4.5, 3.5 × 10-4 mol L-1 and 140 min, respectively. The removal of MB over GO/ZnO was 99% under the optimum conditions and was superior than that over GO and CNT/ZnO. According to Pareto analysis of the modeling, the irradiation time and photocatalyst dosage were the most effective factors on the decolorization efficiency of methylene blue, respectively. <![CDATA[Proximate Composition, Mineral Contents and Fatty Acid Composition of the Different Parts and Dried Peels of Tropical Fruits Cultivated in Brazil]]> The proximate composition, mineral contents and fatty acid composition of different parts (peel, pulp and seeds) of seven tropical fruits were evaluated. Beyond that, this study aims to evaluate the effect of drying processing on peels. Pulp and peel showed highest moisture values (65.7-93.3%), while the seed ranged from 5.8 to 67.2%. The drying processing of peels decreased moisture values (2.3-18.7%). Furthermore, drying processing did not affect ash contents, total crude protein, lipids and fiber values and fatty acid composition for avocado, pineapple, banana, papaya, passion fruit, watermelon and melon. A wide range of mineral contents was noted in different parts of fruit and calcium and potassium were found in larger quantities (25.4 to 4808 mg per 100 g). The fruits exhibited essential fatty acids as omega-6 and omega-3 with the largest contents observed in the peels and seeds (31.4 to 1970 mg per 100 g). <![CDATA[Strontium and Nickel Heterogeneous Catalysts for Biodiesel Production from Macaw Oil]]> It is presented herein heterogeneous catalysts comprised of strontium and nickel oxides synthesized using a coprecipitation method. They were applied for the preparation of biodiesel from macaw palm oil. The catalysts were characterized by X-ray diffraction (XRD), adsorption and desorption of nitrogen by Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and differential thermogravimetric analysis (TG-DTA). The conversion was determined by gas chromatography with flame detector (GC-FID). The best activity was obtained when the catalyst was calcined at 1100 °C for 3 hours. The highest conversion was reached (97%) when the following conditions were used: 5 hours, 2% of metal loading, 65 °C and oil/alcohol molar ratio of 1:9. <![CDATA[PhotoMetrix: An Application for Univariate Calibration and Principal Components Analysis Using Colorimetry on Mobile Devices]]> This article describes the development of a mobile colorimetric analysis tool. The application, called PhotoMetrix, employs the techniques of simple linear correlation for univariate analysis and principal components analysis (PCA) for multivariate exploratory analysis. The image data are captured by the main camera of the device and converted into red, green and blue (RGB) histograms. As regards the application, the iron determinations were performed in vitamin supplements (univariate module) and differentiation of banknotes was performed by PCA (multivariate module). For the iron determinations, three samples of vitamins at concentrations of 14, 40 and 50 mg of iron per tablet were tested and the results were not statistically significant (p &gt; 0.05) compared to the reference method. The differentiation of banknotes was performed on Brazilian and Argentinean banknotes. The results showed clustering of the same types of banknotes, and through the loadings graph it was possible to observe the variables through the formation of clusters. <![CDATA[Acidity and Characterization of 12-Tungstophosphoric Acid Supported on Silica-Alumina]]> This work deals with preparation and characterization of H3PW12O40 (H3PW) supported on silica-alumina. Impregnation of H3PW (15, 20, 30 and 40 wt.%) on commercial silica-alumina support in acidic aqueous solution is effective for preparing this catalyst keeping its Keggin structure, according to different methods of characterization. The catalysts were tested in a model reaction of acetic acid with ethanol and 30 wt.% H3PW/SiO2-Al2O3 had the highest activity under the conditions: catalyst calcination at 300 ºC, temperature of 100 ºC, acetic acid:ethanol molar ratio of 2:1 and catalyst:acetic acid mass ratio of 10 wt.%. The reaction yield was 79 and 100% selectivity for ethyl acetate over three reutilizations, for reaction time of 2 h. The calculated total acid site distribution was 0.299 mmol g-1 (97% of the theoretical probed by pyridine), and most of these (0.236 mmol g-1) were Brønsted weak-medium strength (pyridine desorption between 300 and 500 ºC). <![CDATA[Physicochemical Properties and Field Evaluation of Monolithic Wax Formulations for the Controlled Release of a Forest Pest Pheromone]]> This work shows the way to develop a monolithic device for the release of an active agent. Different waxes to prepare monolithic dispensers were used. Studies to characterize the release rate of the pheromone dispensers, and to determine many physicochemical properties of the active components and waxes utilized as matrices, were conducted. The advantages of using monolithic devices as an insect pheromone dispenser in order to control an insect that attacks commercial poplar plantations were demonstrated. Also, the practical application employing monolithic dispensers manufactured in this paper with the sex pheromone of the ambrosia beetle Megaplatypus mutatus (Coleoptera: Platypodidae) was verified. This forest pest is known to attack tree plantations in South America. The release rates were mainly dependent of matrix hardness and viscosity, as well as the particle size of fillers. A good performance of the formulated monolithic dispensers was observed during the field trials, with a reduction of damage levels of 40%. <![CDATA[Analysis of Xanthine Oxidase Inhibitors from <em>Puerariae flos</em> Using Centrifugal Ultrafiltration Coupled with HPLC-MS]]> In this study, centrifugal ultrafiltration coupled with high performance liquid chromatography-mass spectrometry was utilized to screen and identify xanthine oxidase inhibitors from Puerariae flos extract. The experimental conditions of centrifugal ultrafiltration including xanthine oxidase concentration, incubation time, pH and temperature were optimized. At the optimum condition (xanthine oxidase concentration: 30.0 μg mL-1, incubation time: 20 min, pH 7.0 and temperature: 25 ºC), four compounds were successfully screened from P. flos extract and identified as tectoridin, daidzin, ononin and biochanin A. The yields of tectoridin, daidzin, ononin and biochanin A were 0.231, 0.117, 0.303 and 0.089 g from 50.0 g crude P. flos samples. The inhibitory activities of these compounds were verified by xanthine oxidase inhibition assays. The experimental half maximal inhibitory concentration (IC50) values of tectoridin, daidzin, ononin and biochanin A were 88.5, 85.1, 88.8 and 87.0 μmol L-1, and the binding degree of them were 5.70, 8.28, 6.31 and 37.83% at the optimum condition, respectively. The proposed method provided a rapid and effective way to screen and analyze active compounds from natural products. <![CDATA[A New Furanoheliangolide Sesquiterpene Lactone from <em>Calea pinnatifida</em> (R. Br.) Less. (Asteraceae) and Evaluation of Its Trypanocidal and Leishmanicidal Activities]]> Calea pinnatifida (R. Br.) Less. is commonly known in Brazil as "cipó-cruz", "quebra-tudo" or "aruca". This species is employed in folk medicine as giardicidal, amoebicidal and to treat digestive disorders. The present paper describes the isolation and structure determination of a new furanoheliangolide sesquiterpene lactone named 11,13-dihydroxy-calaxin, in addition to seven known compounds: ethyl caffeate, vanillin, 12-hydroxy-encecalin, phytol, 3,4-di-O-caffeoylquinic acid, 3,5-di-O-caffeoylquinic acid and 4,5-di-O-caffeoylquinic acid from the ethanol extract of C. pinnatifida leaves. Additionally, 11,13-dihydroxy-calaxin, vanillin, 12-hydroxy-encecalin, phytol, 3,4-di-O-caffeoylquinic acid, 4,5-di-O-caffeoylquinic acid and the mixture of 3,4-di-O-caffeoylquinic, 3,5-di-O-caffeoylquinic and 4,5-di-O-caffeoylquinic acids were assayed against the amastigote forms of Leishmania amazonensis and Trypanosoma cruzi, and the sesquiterpene lactone 11,13-dihydroxy-calaxin exhibited a promising trypanocidal and leishmanicidal activity, displaying IC50 values of 5.27 and 8.30 µM, respectively. <![CDATA[Multielement Determination of Macro and Micro Contents in Medicinal Plants and Phytomedicines from Brazil by ICP OES]]> In this study, the elemental composition of nine medicinal plants and phytomedicines was evaluated by using axial view inductively coupled plasma optical emission spectrometry (ICP OES) after three digestion procedures: dry ashing (DA) and two wet digestions with a mineral acid (HNO3/H2O2) mixture on a conventional hot plate (CD), besides microwave digestion (MW). Accuracy was assessed from spinach leaves (CRM 1570a) and recovery values were in the range of 82 to 113.8%. Precisions, such as relative standard deviation (RSD), below 10% were reached. The MW procedure was preferred for its accuracy (recovery values of 94 to 102%), reduced contamination, increase in the efficiency of the decomposition process, lower residual acidity and reduced time required for digestion. The concentrations of analytes in the samples (minimum-maximum in μg g-1) were: Ca (100.71-462.20), Co (0.54-0.85), Cu (0.32-7.82), Fe (2.74-18.03), Mg (18.40-521.28), Mn (0.17-55.14), Ni (0.56-1.25) and Zn (2.96-20.92). The levels of Al, Ba, Cd, Cr, Mo, Pb, Se and V in all investigated samples were found to be below the limit of detection of ICP OES. The multielement analysis by ICP OES showed that the method is simple, fast and reliable for the multielement determination in medicinal plants and phytomedicines. <![CDATA[Non-Invasive Detection of Adulterated Olive Oil in Full Bottles Using Time-Domain NMR Relaxometry]]> A fast procedure using time-domain nuclear magnetic resonance (TD-NMR) to detect olive oil adulteration with polyunsaturated vegetable oils in filled bottles is proposed. The 1H transverse relaxation times (T2) of 37 commercial samples were measured using low-field nuclear magnetic resonance (LF-NMR) spectrometer and a unilateral nuclear magnetic resonance (UNMR) sensor. Results obtained with LF-NMR revealed better feasibility when compared with the UNMR sensor, with higher signal-to-noise (S/N) ratio and larger difference in the T2 decays. Principal component analysis (PCA) exhibited tight and well-separated clusters of pure olive oil (OO), pure soybean oil (SO), and blends of OO/SO (adulterated samples). Soft independent modeling of class analogies analysis (SIMCA) classification model indicated that five brands of olive oil commercialized in Brazil were adulterated with polyunsaturated fatty acids, further confirmed by high-resolution NMR. Overall, LF-NMR provided a fast procedure for screening olive oil authenticity directly in the sealed bottles.