Scielo RSS <![CDATA[Journal of the Brazilian Chemical Society]]> vol. 29 num. 6 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Ultrasound-Promoted Chemoselective Oxysulfonylation of Alkenes]]> The ultrasound-assisted oxysulfonylation of different alkenes using sodium salts of organosulfinic acids under air atmosphere is described. The reaction is chemo- and regioselective and the corresponding β-keto-sulfones were obtained in good yields as major products. The use of ultrasound greatly accelerated the formation of products when compared to the conventional methods. <![CDATA[Rhodium(III)-Catalyzed Addition of Indoles with Boc-Imines via C-H Bond Activation]]> A rhodium-catalyzed alkylation reaction of indoles with N-Boc-imines has been developed via C-H activation to afford a series of substituted 2-indolyl-methanamine derivatives with good functional group tolerance and regioselectivity. A wide range of indole-based alkylation products could be obtained in up to 95% yield. <![CDATA[Impact of Cafeteria Diet on the Composition of Fatty Acids in Zebrafish (Danio rerio) Fillets]]> The cafeteria diet is widely used as a model for inducing obesity in animals, and the zebrafish (Danio rerio) has emerged as a promising model for this purpose. In this context, this study evaluated the effect of a cafeteria diet on the composition of fatty acids in zebrafish fillets. Zebrafish grown in tanks for a period of 60 days were treated with standard (ST) and cafeteria (CAF) diets. The CAF diet presented higher total lipid and energy values than ST diet, due to the addition of peanut, chocolate and biscuit in its preparation. Moreover, CAF diet showed the highest concentrations of palmitic (19.44 ± 0.55 mg g-1), oleic (102.58 ± 2.85 mg g-1) and linoleic (44.47 ± 1.32 mg g-1) acids. A significant increase in oleic and linoleic acid concentrations (39.77 ± 2.69 and 14.31 ± 0.86 mg g-1, respectively) and in the omega-6/omega-3 ratio (11.52 ± 0.81) was observed in the zebrafish fillets between 0 and 60 days for CAF diet, indicating incorporation of these fatty acids. <![CDATA[Use of Mixture Design with Minimal Restrictions to Optimize an Extraction Procedure Employing Diluted Acids Assisted by Ultrasound and Microwave for Nutrient Element Determination in Vegetal Samples]]> In this work, it was developed an alternative analytical strategy for the preparation of vegetal samples extracted with diluted acids and assisted by ultrasound and microwave radiation for the determination of nutrients elements by fast sequential flame atomic absorption spectrometer. The conditions optimized using univariate and multivariate methodologies for the procedure were as follows: 200 mg of sample; extraction solution comprising a mixture of 6.3 mL HNO3, 2.1 mL HCl, and 1.7 mL CH3COOH; extractor with a final concentration of 2.5 mol L-1; a sonication time of 30 min; and a microwave radiation time of 6 s. The accuracy of the procedure was confirmed by analyzing the certified reference material NIST 1515 (apple leaves) and by comparison with the results obtained through microwave-assisted total digestion method. The procedure was applied to determine Ca, Mg, Cu, Mn, Fe, and Zn in several cassava peel samples used in animal nutrition, and proved to be simple, reliable, fast, easy to implement, and inexpensive. <![CDATA[Photophysical and Photochemical Properties and Aggregation Behavior of Phthalocyanine and Naphthalocyanine Derivatives]]> The photophysical and photochemical properties of phthalocyanine and naphthalocyanine with similar structures were studied in solution and with density-functional theory (DFT) computational method. The extended π-conjugated system in naphthalocyanines causes a bathochromic shift in UV-Vis, emission and excitation bands, and promotes lesser generation of singlet oxygen in solution when compared to phthalocyanines. Time dependent DFT (TD-DFT) calculations point out the molecular orbitals involved in Q-band transition, corresponding to highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) transition with a concentration of charge along x-axis, while the transition to LUMO+1 is in y-axis direction. The presence of tert-butyl substituents does not affect the molecular orbitals shape, but affect their energies. Aggregation studies in dimethyl sulfoxide (DMSO):water solutions showed that naphthalocyanines studied have more aggregation tendency than the phthalocyanines. DFT studies indicated that stacked-dimers are preferred to rotated-stacked conformation due the interaction between ZnII and nitrogen atom from different monomers. <![CDATA[Syntheses, Experimental and Theoretical Studies on Absorption/Emission Properties of Pyrazoline-Containing Aryl/Methoxynaphthyl Substituents]]> 5-Aryl-3-(2-methoxynaphthalen-6-yl)-1-phenylpyrazoline derivatives were synthesized starting from (E)-1-(3-aryl)-(2-methoxynaphthalen-6-yl)-prop-2-en-1-one and phenylhydrazine. The compounds were characterized by 1H and 13C nuclear magnetic resonance (NMR), elemental analyses and mass spectrometry. Some compounds showed promising luminescence properties in solution and in solid state; the absorption and emission characteristics were measured and the fluorescence quantum yield of two of the derivatives [4,5-dihydro-3-(2-methoxynaphthalen-6-yl)-5-(3,4,5-trimethoxyphenyl)-1-phenyl-1 H -pyrazoline and 5-(4-chlorophenyl)-4,5-dihydro-3-(2-methoxynaphthalen-6-yl)-1-phenyl-1 H -pyrazoline] were found to have excellent values compared to rhodamine B standard. Theoretical calculations at time-dependent density functional theory (TD-DFT) level are in agreement with the experimental measurements and are helpful to explain the electronic behavior. <![CDATA[Continuous Synthesis of a Green Fuel Additive Mixture with Highest Quantities of Solketalacetin and Solketal and Lowest Amount of Diacetin from Biodiesel-Derived Glycerol]]> This work presents a continuous, easy-to-scale-up system for glycerol conversion to a valuable fuel additive mixture such as solketalacetin ((2,2-dimethyl-1,3-dioxolan-4-yl)methyl acetate), solketal and minimum amount of diacetin with no byproducts. A two-stage reaction was conducted to synthesize the mixture. At first, glycerol was reacted with acetic acid in a continuous system to synthesize monoacetin using a small plug flow reactor and central composite design to optimize the variables related to monoacetin synthesis. Finally, an acetic acid:glycerol mole ratio of 3.7:1, a temperature of 79 °C, a flow rate of 0.9 mL min-1, and a pressure of 1 bar were determined as the optimum conditions. At the optimum condition, predicted and experimental yields of monoacetin were 63 and 62%, respectively. In the next stage, monoacetin and the residual glycerol were reacted with acetone to obtain a mixture of solketalacetin, solketal, and diacetin with the mole percentage of 62, 30, and 8%, respectively. <![CDATA[Synthesis of Chelating Agent Free-Solid Phase Extractor (CAF-SPE) Based on New SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub>/SnO<sub>2</sub> Ternary Oxide and Application for Online Preconcentration of Pb<sup>2+</sup> Coupled with FAAS]]> A new online solid phase preconcentration method using the new SiO2/Al2O3/SnO2 ternary oxide (designated as SiAlSn) as chelating agent free-solid phase extractor (CAF-SPE) coupled to flame atomic absorption spectrometry (FAAS) for Pb2+ determination at trace levels in different kind of samples is proposed. The solid adsorbent has been characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron miscroscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray fluorescence spectroscopy (XRF) and textural data. The method involves the preconcentration using time-based sampling of Pb2+ solution at pH 4.3 through 100.0 mg of packed adsorbed into a mini-column under flow rate of 4.0 mL min-1 during 5 min. The elution step was accomplished by using 1.0 mol L-1 HCl. A wide range of analytical curve (5.0-400.0 µg L-1), high enrichment factor (40.5), low consumption index (0.5 mL) and low limits of quantification and detection, 5.0 and 1.5 µg L-1, respectively, were obtained with the developed method. Practical application of method was tested on water samples, chocolate powder, Ginkgo biloba and sediment (certified reference material). On the basis of the results, the SiAlSn can be considered an effective adsorbent belonging to the class of CAF-SPE for Pb2+ determination from different matrices. <![CDATA[Enhanced Detection of Ponceau 4R Food Dye by Glassy Carbon Electrode Modified with Reduced Graphene Oxide]]> This paper reports the development of a glassy carbon electrode modified with a reduced graphene oxide (r-GO/GCE) for the determination of the food dye named Ponceau 4R (PNC). The modified sensor presented excellent signal gain in relation to the GCE and GCE modified with graphene oxide besides exhibiting well defined oxidation peaks for PNC at potential of 0.61 V. Through the application of square wave voltammetry using the medium of 0.1 mol L-1 Britton-Robinson (BR) buffer (pH 5.0), analytical curves were constructed under optimized conditions, where linear regions were found within the range of 0.200 to 20.0 μmol L-1. The limits of detection and quantification were 2.84 × 10-8 and 9.46 × 10-8mol L-1, respectively. The sensor was successfully applied towards the determination of PNC in instant juice sample. A comparison made between the result obtained through the application of this sensor and via the high-performance liquid chromatography (HPLC) technique showed no significant difference between the two methods. <![CDATA[Influence of Environmental Factors and Cultural Methods on the Content of N,N-Dimethyltryptamine in Psychotriaviridis (Rubiaceae)]]> Psychotria viridis is one of the species that produces N,N-dimethyltryptamine. Its decoction together with other species, such as Banisteriopsis caapi, produces ayahuasca, a beverage used for ritualistic and medicinal purposes. The goal of this study was to understand how environmental factors and cultivation methods influenced the content of N,N-dimethyltryptamine in P. viridis. Over all four seasons, leaf samples were collected from 25 different locations in 14 Brazilian states, and Federal District. Environmental parameters, micro and macronutrients, plant characteristics, information on farming methods were correlated with N,N-dimethyltryptamine content, determined by gas chromatography coupled to mass spectrometry (GC-MS). Greatest effects on the N,N-dimethyltryptamine amount were associated with seasonality, altitude, latitude and biome type. A positive correlation between N and Mg content and N,N-dimethyltryptamine levels was statistically established. By regression analysis, the adequate foliar nutrient levels that would result in the concentration of N,N-dimethyltryptamine in cultivated plants similar to that of Amazonian P. viridis were equated. <![CDATA[Structure/Activity of Pt<sup>II</sup>/N,N-Disubstituted-N'-acylthiourea Complexes: Anti-Tumor and Anti-Mycobacterium tuberculosis Activities]]> The syntheses, characterization, cytotoxicity against tumor cells and anti-Mycobacterium tuberculosis activity assays of PtII/PPh3/N,N-disubstituted-N'-acylthioureas complexes with general formulae [Pt(PPh3)2(L)]PF6, PPh3 = triphenylphosphine; L = N,N-disubstituted-N'-acylthiourea, are here reported. The complexes were characterized by elemental analysis, molar conductivity, infrared (IR), nuclear magnetic resonance (NMR) (1H, 13C{1H} and 31P{1H}) spectroscopy. The 31P{1H} NMR data are consistent with the presence of two PPh3 ligands cis to each other position, and one N,N-disubstituted-N'-acylthiourea coordinated to the metal through O and S, in a chelate form. The structures of the complexes were determined by X-ray crystallography, forming distorted square-planar structures. The complexes were tested in human cell lines carcinomas and also screened with respect to their anti-Mycobacterium tuberculosis activity (H37RvATCC 27294). It was found that complexes with N,N-disubstituted-N'-acylthiourea containing open and small chains as R2 groups show higher cytotoxic and higher anti-Mycobacterium tuberculosis activity than those containing rings in this position. <![CDATA[In vitro Evaluation of Oxidative Stress Caused by Fine Particles (PM<sub>2.5</sub>) Exhausted from Heavy-Duty Vehicles Using Diesel/Biodiesel Blends under Real World Conditions]]> In this work, the redox activity of fine diesel/biodiesel particulate matter (PM2.5) was studied in order to approach its toxicity from reactive oxygen species, due to adverse effects it may cause to human health. The oxidative potential was measured by the dithiothreitol (DTT) assay in order to study the relative contribution of water-soluble transition metals, polycyclic aromatic compounds (PAH), nitro-PAH, and quinones. It was analyzed a total of 24 samples collected from primarily diesel/biodiesel-exhausted particles from buses. The rate concentrations of PM2.5 redox activity ranged 0.020-0.069 nmol min-1 μg-1, with median at 0.040 nmol min-1 μg-1 (on average, 0.042 ± 0.005 nmol min-1 μg-1 for morning, 0.033 ± 0.007 nmol min-1 μg-1 for afternoon and 0.045 ± 0.009 nmol min-1 μg-1 for night). The transition metals appear to dominate the DTT response, since they were responsible up to 89% of redox activity measured in the samples. Apparently, the metal fraction contained in PM2.5 demonstrated a greater ability to catalyze reactions that promote the formation of reactive oxygen species when compared to organic compounds. It was observed that the oxidative potential of PM2.5 particles emitted from diesel/biodiesel (B7) is similar to diesel-emitted particles. <![CDATA[A Practical Fluorescence-Based Screening Protocol for Polyethylene Terephthalate Degrading Microorganisms]]> We propose a practical, low-cost and selective fluorescence-based protocol adapted to identify polyethylene terephthalate (PET) degrading microorganisms. The microbial hydrolysis of PET nanoparticles was monitored by 2-hydroxyterephthalate, a fluorophore produced in situ after radical hydroxylation of terephthalic acid (TPA), the final hydrolysis product, by the Fenton reaction. Seven fungi presenting promising PET hydrolytic potential using the proposed microscale screening assay were identified. The strains evaluated presented a substantial increase of up to 18-fold in PET nanoparticles conversion, such as obtained by the fungus Trichoderma sp. C70, after their cultivation in a PET-enriched medium. The formation of other hydrolysis products, along with TPA, was observed using matrix assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). <![CDATA[Kavalactones and Benzoic Acid Derivatives from Leaves of Piper fuligineum Kunth (Piperaceae)]]> The known kavalactones (E)-4-methoxy-6-styryl-2H-pyran-2-one, 4-methoxy-6-(3-phenyloxiran-2-yl)-2H-pyran-2-one, 6-(1,2-dihydroxy-2-phenylethyl)-4-methoxy-2H-pyran-2-one, the three benzoic acid derivatives methyl-4-methoxy-3-(3'-methyl-2'-butenyl)benzoate and methyl 2,2-dimethyl-4-oxochroman-6-carboxylate, and a new methyl 4-methoxy-3-(3-methylbut-2-enoyl)benzoate were isolated from the ethanolic extract of Piper fuligineum. The structures of these compounds were determined by using a combination of spectroscopic methods, including 1D- and 2D-nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. This is the first report of the chemical study of P. fuligineum, and the methyl 4-methoxy-3-(3-methylbut-2-enoyl)benzoate is described as a new natural product. <![CDATA[Air Quality Indexes in the City of Rio de Janeiro During the 2016 Olympic and Paralympic Games]]> In this work, the air quality indexes (AQIs) determined in Rio de Janeiro from July to September 2016, before and during the Summer Olympic and Paralympic Games, in the monitoring stations operated by the Municipal Secretariat of the Environment, were compiled and analyzed. Only four automatic monitoring stations determined all the Brazilian criteria pollutants (smog, total particulate matter, PM10 (particulate matter &lt; 10 mm), NO2, ozone and SO2). NO2 and PM10 levels were generally lower during the Olympic period because of restrictions on vehicular flux. However, ozone concentrations remained high, due to unfavorable meteorological conditions. The worst conditions were observed in Bangu and Irajá Districts, where ozone concentrations frequently exceeded 160 mg m-3. According to the World Health Organization (WHO), as ozone concentrations increase above this value, health effects became increasingly numerous and more severe. Brazilian air quality allowable standards are clearly higher than WHO guidelines, which, in addition to the combined results of the adopted air quality indexes and the use of a restricted number of criteria pollutants to report the air quality, led to AQIs in the intervals good and moderate, despite concentrations frequently being high in terms of WHO guidelines. <![CDATA[Synthesis and Antimicrobial Activity of Glycosylated 2-Aryl-5-amidinobenzimidazoles]]> A series of new glycosylated 2-aryl-5-amidinobenzimidazoles derived from four different carbohydrates (D-glucose, D-galactose, N-acetyl-D-glucosamine and lactose) were synthesized by the condensation of the appropriate 4-formyl-3-methoxyphenyl glycoside with 4-amidino- or 4-N-isopropylamidino-ortho-phenylenediamine hydrochloride. All the compounds were properly characterized by high resolution mass spectrometry, uni- and bidimensional 1H and 13C nuclear magnetic resonance and then were evaluated for their antibacterial and antifungal potential. Considering the antifungal potential of them, two derivatives were active against Candida parapsilosis at 96.4 µmol L-1 and another was active against this same strain at 83.5 µmol L-1. In addition, one benzamidine showed activity against Candida glabrata at 97 µmol L-1. Considering the antibacterial potential of these compounds, six of them showed better activity against three different stains: three of them with IC50 of 96.4, 97 and 83.5 μmol L-1 against Gram-positive Micrococcus luteus, the other two with IC50 96.5 and 96.4 μmol L-1 against Gram-positive Enterococcus faecalis and one against Gram-negative Escherichia coli at 90.5 µmol L-1. These findings suggest this structural pattern can be employed for design of more potent agents for discovery of new antimicrobial drug candidates. <![CDATA[Leaves from the Tree Poincianella pluviosa as a Renewable Source of Antiplasmodial Compounds against Chloroquine-Resistant Plasmodium falciparum]]> Poincianella pluviosa is a tree whose stem bark is reputed to have antidiarrheal, wound healing, antitumoral and antimalarial properties. Considering that the leaves of the tree are a more abundant and renewable source than the stem bark, we chose to study the antimalarial potential of this organ part. The aqueous leaf extract exhibited a rich phenolic profile. It was active (IC50= 6.88 ± 1.64 µg mL-1) against chloroquine resistant Plasmodium falciparum (W2) without toxicity to HepG2 A16 cells. The organic fraction was more active (IC50= 1.83 µg mL-1) than the aqueous leaf extract itself. Ten phenolic compounds were obtained from the latter. This is the first report on the phenolic composition of P. pluviosa leaves. Ellagic acid (IC50= 0.215 ± 0.007 µg mL-1) proved to be 32 fold more active than the aqueous leaf extract itself. Considering their renewable aspect, leaves of P. pluviosa appear to be a more interesting source of antimalarial compounds than stem bark. <![CDATA[Identification of Ethyl and t-Butyl Glyceryl Ethers Using Gas Chromatography Coupled with Mass Spectrometry]]> The ethers produced through the etherification reaction of glycerol with ethanol or t-butanol are used as oxygenated fuel additives, intermediates in the pharmaceutical industry, and non-ionic surfactants. However, the identification of these ethers has not been accurately done, because only some mass spectra of these compounds are available in the libraries. Moreover, there is a lack of discussion on their identification in the literature. In this work, a detailed identification of all ethers produced in the etherification of glycerol with ethanol or t-butanol was performed considering the mass spectra of isolated products and the comparison of the retention times. The elution order of the products was: tri-alkyl, 1,3-dialkyl, 2,3-dialkyl, 3-monoalkyl and 2-monoalkyl. In all mass spectra of the ethyl ethers, the base peak was m/z 61, while in the case of t-butyl ethers it was m/z 57. <![CDATA[Determination of Alkyl Esters Content by Gas Chromatography: Validation of Method Based on Short Column and Response Factor]]> In this study an analytical method, based on gas chromatography with flame ionization detection, using a short column and response factor (GCSCRF), was validated for the quantification of fatty acid alkyl esters (methylic or ethylic). During the validation process, the proposed method was employed to analyze twenty samples of fatty acid methyl esters and fatty acid ethyl esters. Biodiesel samples were produced from soybean oil and the validated method was found to be selective, being able to separate and identify every ester species present in the samples according to its carbon number. When the method was submitted to some variations in the sample preparation procedure, it remained robust. Limits of detection and quantification were 6.76 and 20.4 mg mL-1, respectively. The suggested method also showed great precision when successive analyses were carried out for different analysts, with standard deviation (SD) 0.6 for repeatibility and relative standard deviation (RSD) percentage 7.3% for intermediate precision, excellent accuracy when compared to other reference methods (EN 14103 and high-performance liquid chromatography with ultraviolet dection (HPLC-UV)) and recovery studies. <![CDATA[Chain Elongation Influence in Copolymerization with Different Diesters of Norbornene 2,3-Dicarboxylic Acid Monomers via ROMP under Air Atmosphere]]> Diesters of norbornene 2,3-dicarboxylic acid (NBE-(COOR)2), in which R is an alkyl group, were synthesized from one-pot synthesis method with 5-norbornene-2,3-dicarboxylic acid and methanol and ethanol. The new monomers were, respectively, the dimethyl ester NBE-(COOCH3)2 and diethyl ester NBE-(COOCH2CH3)2. Norbornene was mixed with these monomers at different proportions and copolymerized via ring-opening metathesis polymerization (ROMP) with 1st generation Grubbs' catalyst. All experiments were conducted under air atmosphere to obtain the isolated polymer. Yield results show that elongation of the R group influenced the copolymerization process. At the same co-monomer proportion, the yield decreases as a function of the R group elongation. Thermogravimetric analysis (TGA) was performed and, in all cases, more than one thermal degradation process was observed. The first process was assigned to pendent group degradation, whereas the second process was assigned to main chain degradation. These thermal processes were also influenced by different elongation of the aliphatic group of the pendent chain. <![CDATA[Multi-Residue Method for Determination of Thirty-Five Pesticides, Pharmaceuticals and Personal Care Products in Water Using Ionic Liquid-Dispersive Liquid-Liquid Microextraction Combined with Liquid Chromatography-Tandem Mass Spectrometry]]> Ionic liquid-dispersive liquid-liquid microextraction (IL-DLLME) was used for the determination of different chemical classes of analytes for the first time. Limits of quantification (LOQs) ranged from 0.5 to 2.5 µg L-1, and the linearity ranged from the LOQ of each compound to 50 µg L-1. Recoveries ranged from 70 to 120% for the compounds, with relative standard deviations less than 18%. The proposed method demonstrates for the first time that sample preparation by IL-DLLME and determination by liquid chromatography-tandem mass spectrometry (LC-MS/MS) can be used successfully for the simultaneous extraction of 19 kinds of pesticides and 16 PPCPs from water samples. In addition, to eliminate the environmental risk of waste solvent disposal, this technique uses a low-toxicity extraction solvent. Finally, the analytical method proposed was applied successfully in analysis in surface water samples. <![CDATA[Colorimetric Analysis of Cotton Textile Bleaching through H<sub>2</sub>O<sub>2</sub> Activated by UV Light]]> The bleaching process is one of the steps of cotton fabric manufacture. Traditionally, the most common bleaching procedure is based on the use of a hydrogen peroxide (H2O2) solution in alkali pH associated with high temperature. In this study, we investigated the possibility of applying a photolysis technique, combining ultraviolet (UV) light and H2O2 in acidic pH to promote raw cotton fabric bleaching, without adding heat and stabilizers to the process. A colorimetric analysis was performed to assess the bleaching procedure in the samples. The experiment consisted in moistening cotton fabric samples with H2O2 and then illuminating them with UV light with different doses, ranging from 0.6 to 36 J cm-2. Our findings have shown that it is important to balance the hydrogen peroxide and the amount of delivered UV light to the cotton fabric in order to achieve a satisfactory whiteness without compromising the fabric mechanical properties.