Scielo RSS <![CDATA[Química Nova]]> vol. 38 num. 6 lang. es <![CDATA[SciELO Logo]]> <![CDATA[BIS(4-FLUOROPHENYLSULFONYLDITHIOCARBIMATO)ZINCATE(II) SALTS: NEW ANTIFUNGALS FOR THE CONTROL OF <italic>Botrytis</italic> BLIGHT]]> <p>Botrytis blight or gray mold is a highly destructive disease caused by <italic>Botrytis</italic> spp., that infects flowers, trees vegetables, fruit, especially grapevines and strawberry. Three new compounds with general formula (A)<sub>2</sub>[Zn(4-FC<sub>6</sub>H<sub>4</sub>SO<sub>2</sub>N=CS<sub>2</sub>)<sub>2</sub>], where A = PPh<sub>3</sub>CH<sub>3</sub> (<bold>2a</bold>), PPh<sub>3</sub>C<sub>2</sub>H<sub>5</sub> (<bold>2b</bold>), PPh<sub>3</sub>C<sub>4</sub>H<sub>9</sub> (<bold>2c</bold>), and the previously published compounds where A = PPh<sub>4</sub> (<bold>2d</bold>) and NBu<sub>4</sub> (<bold>2e</bold>), were synthesized by the reaction of 4-fluorophenylsulfonyldithiocarbimate potassium dihydrate and zinc(II) acetate dihydrate with the appropriate counter cations (A) halides. The new compounds were characterized by infrared, <sup>1</sup>H and <sup>13</sup>C NMR spectroscopies. All these salts inhibited the growth of <italic>Botrytis cinerea</italic>, with compounds <bold>2c</bold> and <bold>2d</bold> showing greater antifungal activity than zinc dimethyldithiocarbamate, the active principle of the fungicide Ziram. The bis(dithiocarbimate)zincate(II) salts are also active against the bacteria <italic>Escherichia coli</italic> and <italic>Staphylococcus aureus</italic>.</p> <![CDATA[INFLUENCE OF AGE OF THE LEAVES OF <italic>E. uniflora</italic> L. ON CHEMICAL COMPOSITION OF ESSENTIAL OIL]]> <p>GC-FID, GC-MS and NMR spectral data were used to analyze the composition of the essential oils extracted from young and mature leaves of <italic>E. uniflora</italic> L. grown in Seropédica - RJ. Thirty and twenty-five compounds were identified, corresponding to approximately 98.19% and 93.77% of the total amount of oils, respectively. The major components of the young leaves were (3<italic>Z</italic>,7<italic>E</italic>)-3,7-dimethyl-10-(propan-2-ylidene)cyclodeca-3,7-dienone (germacrone, 34.59%), 4,5,6,7-tetrahydro-3,6-dimethyl-5-(prop-1-en-2-yl)-6-vinylbenzofuran (curzerene, 26.56%) and (1<italic>Z</italic>,5<italic>E</italic>)-1,5-dimethyl-8-(propan-2-ylidene)cyclodeca-1,5-diene (germacrene B, 12.72%), and of the mature leaves were curzerene (35.75%), germacrene B (19.22%) and β-(<italic>E</italic>,1<italic>R</italic>,9<italic>S</italic>)-4,11,11-trimethyl-8-methylenebicyclo[7.2.0]undec-4-ene (caryophyllene, 12.55%). The multivariate analysis applied to data from GC-MS allowed discrimination of the differences in the chemical composition of oils based on the age of the leaves. The components germacrone, curzerene e furanodiene (not observed during conventional chromatographic analysis) were isolated from the essential oil of young leaves. These compounds were characterized by GC-MS, and <sup>1</sup>H and <sup>13</sup>C NMR (1D and 2D).</p> <![CDATA[CHEMICAL CONSTITUENTS FROM THE STEM BARK OF <italic>Annona pickelii</italic> (Annonaceae)]]> <p>The phytochemical investigation of the stem bark of <italic>Annona pickelii</italic> yielded four steroids (β-sitostenone, β-sitosterol, stigmasterol and campesterol), three lignans (eudesmin, magnolin and yangambin), twelve alkaloids (liriodenine, lysicamine, atherospermidine, anonaine, analobine, asimilobine, discretamine, stepholidine, coclaurine, orientaline, juziphine and stepharine), and a benzenoid (2-methoxybenzoic acid). These compounds support their recent reclassification from <italic>Rollinia</italic> to <italic>Annona</italic>, and that it is a typical species of the family Annonaceae. Significant antifungal and antioxidant activities were found for the methanol crude extract as well as for the lignans eudesmin, magnolin, yangambin and the alkaloid discretamine. In addition, several items of NMR data for the alkaloids were reviewed and unequivocally described in this work.</p> <![CDATA[CHARACTERIZATION OF GERMANIUM NANOWIRES SYNTHESIZED USING COPPER AS CATALYST METAL]]> <p>This paper presents reliable synthesis of germanium nanowires by the vapor-liquid-solid method using copper as an alternative catalyst to gold, the most commonly used metal. The morphological study showed long range single-crystalline germanium nanowires with diamond structure and diameters ranging from 20 nm to 80 nm and lengths in tenths of a micrometer, which was much larger than the cross-section. In an investigation of electronic properties, devices built from a thin film of nanowires were studied and the semiconductor behavior of the samples confirmed, with variable range hopping identified as the main transport mechanism. Additionally, metal-nanowire contact behavior - ohmic or with Schottky barrier - was found to depend on the metal used in the device. Therefore, the possibility of controlling current-voltage behavior combined with the good crystalline quality of the nanowires renders these nanostructures an attractive option for future electronic and optoelectronic applications.</p> <![CDATA[DEVELOPMENT OF ORAL NIFEDIPINE-LOADED POLYMERIC NANOCAPSULES: PHYSICOCHEMICAL CHARACTERISATION, PHOTOSTABILITY STUDIES, <italic>IN VITRO</italic> AND <italic>IN VIVO</italic> EVALUATION]]> <p>In this study, nifedipine (NFP)-loaded polymeric nanocapsules were prepared and characterised with a view to protect the drug from degradation. Nanocapsule suspensions were prepared using two different surfactants (pluronic F68 and polyvinyl alcohol). Physicochemical stability and <italic>in vivo</italic>antihypertensive effect were evaluated. The particle size, zeta potential and entrapment efficiency remained constant during a period of 28 days of exposure under light irradiation. A smaller particle size and a higher zeta potential were obtained for the nanocapsules prepared with Pluronic F68 as surfactant. The solid drug and the nanocapsules were submitted to light exposure for 28 days. After this period of time, the percentage of drug remaining in the PF68NFP and PVANFP nanocapsules was 28.1% and 21.3%, respectively. In contrast, the solid drug was completely degraded after 4 days, suggesting that the nanocapsule suspensions promoted significant protection of the drug against light exposure. In addition, <italic>in vivo</italic> studies were carried out, which demonstrated that the formulations with polyvinyl alcohol exhibited a very rapid onset of action after oral administration in rats and led to faster drug release. The nanoparticles developed can be considered as an alternative for improving NFP stability in liquid formulations.</p> <![CDATA[ASSOCIATION OF BRANCHED POLYETHYLENE IMINE WITH SURFACTANTS IN AQUEOUS SOLUTION]]> <p>Three polymer-surfactant systems comprised of branched polyethylene imine (PEI) with an anionic surfactant (sodium dodecylsulfate; SDS), a cationic surfactant (tetradecyltrimethylammonium bromide; TTAB), and a zwitterionic surfactant (<italic>N</italic>-tetradecyl-<italic>N</italic>,<italic>N</italic>-dimethyl-3-ammonio-1-propanesulfonate; SB3-14) were studied based on the properties of surface tension, pyrene fluorescence emission, dynamic light scattering, pH, and zeta potential measurements. The critical aggregation concentration (<italic>cac</italic>) and polymer saturation point (<italic>psp</italic>) were determined for all three systems. The effect of these surfactants on the physico-chemical characteristics (diameter and surface charge) of the complexes formed was determined. Polymer-surfactant interactions occurred in all of the systems studied, with the strongest interactions, electrostatic in nature, occurring in the SDS-PEI system. After the neutralization of the polymer charges with the addition of the surfactant, the hydrophobic effect started to control the interlacing of the polymer chains. For the PEI-TTAB system, a very dense film was formed at surfactant concentrations above 2.0 mmol L<sup>-1</sup>. In this case, the bromide counter-ion interacted with both the positively-charged PEI and the head of the surfactant, which is responsible for the formation of double layer coordination complexes. For the system composed of PEI and the zwitterionic surfactant, less cooperative associations occurred in comparison with the other systems.</p> <![CDATA[IDENTIFICATION OF ORGANIC COMPOUNDS IN A MUNICIPAL LANDFILL LEACHATE BY GAS CHROMATOGRAPHY COUPLED WITH MASS SPECTROMETRY]]> <p>The organic compounds present in leachate can contaminate soil, superficial and underground water, and the majority is considered harmful to the environment and human health. The objective of this study was to identify organic compounds present in landfill leachate located in Maringá-PR by gas chromatography coupled to mass spectrometry (GC-MS). The raw leachate was characterized by measurements of pH, Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOQ), Dissolved Organic Carbon (DOC), apparent and true colors, turbidity and absorbance at 254 nm. The extraction of organic compounds in leachate was carried out by liquid-liquid extraction (LLE) with ethyl acetate and dichloromethane solvents, while varying the pH and ionic strength. The analysis of the leachate by GC-MS showed the presence of compounds considered to have toxic effects on the environment and human health, such as pesticides and phenolic compounds. Several compounds containing oxygenated groups such as carboxylic acids and alcohols were also identified, indicating that it was highly probable that the decomposition of waste in the landfill was in the acidogenic phase.</p> <![CDATA[SIMULTANEOUS VOLTAMMETRIC DETERMINATION OF AMLODIPINE BESYLATE AND HYDROCHLOROTHIAZIDE IN SYNTHETIC URINE SAMPLES USING A BORON-DOPED DIAMOND ELECTRODE]]> <p>A novel method for simultaneous voltammetric determination of the antihypertensive drugs, amlodipine besylate (AML) and hydrochlorothiazide (HTZ) in synthetic urine samples was developed. Determination was carried out with a cathodically pretreated boron-doped diamond electrode (CPT-BDD) using square-wave voltammetry (SWV) and Britton-Robinson buffer solution at pH 2 as the supporting electrolyte. AML and HTZ exhibited oxidation peaks at 0.88 V and 1.30 V, respectively. The difference in potentials of 0.42 V allowed the simultaneous determination of these two analytes. The analytical curve showed linear response in the concentration range from 0.200 to 9.09 µmol L<sup>-1</sup> for AML and from 4.00 to 100 µmol L<sup>-1</sup> for HTZ, with a limit of detection (LOD) of 60.0 nmol L<sup>-1</sup> and of 2.00 µmol L<sup>-1</sup> for AML and HTZ, respectively. Recoveries of these analytes ranged from 91.0 to 107%. The proposed method using SWV and a CPT-BDD electrode is simple, fast and low cost, representing a good alternative for simultaneous determination of AML and HTZ in urine samples.</p> <![CDATA[DEVELOPMENT OF A SAMPLE PREPARATION METHOD FOR RAW MATERIAL EVALUATION OF SCHOOL SUPPLIES]]> <p>The aim of this study was to evaluate the extraction of elements Ba, Cd, Cr, Hg and Pb in solid samples, using a microwave oven with closed flasks and to understand the physicochemical parameters involved in this process. The conducting of this study was based on directive 2009/48/CE, which specifies the levels of elements in the materials used by children. A total of eight samples were used to evaluate the extraction process. A full factorial design 2<sup>3</sup> was performed and principal component analysis (PCA) was used to select only critical samples (simultaneously high residual solid content and metal concentrations) for the proposed process, reducing the number of samples tested. A second full factorial design 2<sup>3</sup> was performed with selected samples (masterbatch, polymer and kaolin) and the following variables investigated: addition of H<sub>2</sub>O<sub>2</sub>, addition of analytes, and HNO<sub>3</sub> volume. The responses observed for this factorial design were recoveries of the analytes (Ba, Cd, Cr, Hg, and Pb) and a desirability function was used in order to combine all responses. The conclusions were that it is not possible to digest some samples with different physicochemical characteristics (masterbatch and polymer, for example) in the same batch and that the proposed system can be used to perform sample screening.</p> <![CDATA[PHYTOCHEMICAL AND PHYLOGENETIC ANALYSIS OF <italic>Spondias</italic>(Anacardiaceae)]]> <p>This paper describes the correlation between the phenolic composition and the molecular phylogenetic reconstruction of five <italic>Spondias</italic> species (Anacardiaceae). Two of these species (<italic>S. venulosa</italic> and <italic>Spondias</italic> sp.) occur in rainforest areas and the other three are widely distributed in Brazil (<italic>S. dulcis</italic>, <italic>S.mombin</italic>, and <italic>S. purpurea</italic>). The flavonoid enriched fraction of the <italic>S. venulosa</italic> leaf extract also underwent a chemical study. The results indicate that the presence of flavonol 3-<italic>O</italic>-glycosides are a synapomorphic character of the studied American <italic>Spondias</italic> and the production of rhamnetin 3-<italic>O</italic>-rutinoside is a synapomorphy of the Atlantic forest species. This is the first report of flavonoids in <italic>S. venulosa</italic>, an endemic species from the Brazilian Atlantic rainforest.</p> <![CDATA[STOCHASTIC BIOSENSING BY A SINGLE PROTEIN NANOPORE IN THE DEVELOPMENT OF ANALYTICAL TOOLS]]> <p>Studies employing a single protein nanopore as a molecular recognition element in the development of analytical devices - biosensors, spectrometers, DNA sequencing - have increased considerably in the last decade. Several studies show the potential of these bionanostructures for future stochastic biosensing technology. Stochastic biosensing is an approach that relies on the observation of individual binding events between analyte molecules and a single receptor. This approach is inherent to the organisms that use a single protein nanopore as a key element to start, manage and maintain the chemical and biophysical processes of living cells. Here, we discuss alpha-toxin as a bacterial exotoxin and prototype of a protein nanopore in real-time detection and characterization of molecules in aqueous systems.</p> <![CDATA[BIOMETHANOL PRODUCTION VIA GASIFICATION OF LIGNOCELLULOSIC BIOMASS]]> <p>With rising global energy demands and the perception of an imminent lack of petroleum, a main source of energy, comes a big rush for renewable and sustainable energetic sources. In Brazil, a reasonable fraction of energy comes from biomass, a renewable source with increasing energetic potential, not only for the direct production of energy in combustion but also as feedstock in the chemical industry. In this context, Bio-Methanol arises as one of the possible substitutes for petroleum fuels, since it can come from renewable sources, has excellent fuel properties and low CO<sub>2</sub> emissions. Bio-Methanol produced from biomass via gasification is well known, and its advantages are increasing, with new studies and technologies appearing around the process. This literature review summarizes recent technology for bio-methanol production and the economics of large-scale applications, presenting the advantages of the process along with the future prospects of bio-methanol in Brazil.</p> <![CDATA[MULTIVARIATE IMAGE ANALYSIS IN CHEMISTRY: pH MEASUREMENTS OF DRINKING WATER]]> <p>A Multivariate Image Analysis (MIA) laboratory activity was proposed estimating pH of drinking water samples from its digital images after adding bromothymol blue as a pH indicator, and using the PLS multivariate calibration method. All computational work was done using GNU Octave free software. The MIA-PLS based approach exemplified with drinking water pH estimates is tailored to meet the needs of both students and researchers. MIA-PLS method was statically equivalent to the reference method using a conventional glass pH electrode. This lab activity combines analytical methodology, computing, and chemometrics.</p> <![CDATA[EVALUATION OF DIFFERENT COLORIMETRIC REAGENTS FOR THE DETERMINATION OF FORMALDEHYDE IN INDOOR ENVIRONMENTS]]> <p>Different colorimetric reagents, the Nash reagent (acetylacetone/ammonia solution), Purpald (4-amino- 3-hydrazino-5-mercapto-1,2,4-triazole/sodium hydroxide solution) and 3-methyl-2-benzothiazolinone hydrazone (MBTH), were evaluated for the determination of formaldehyde in indoor air samples. Analytical parameters such as color stability of the product formed, sampling efficiency and reaction conditions were compared for the methodologies. Several method validation parameters were determined for the three colorimetric methods. The MBTH method showed better results and was used for the determination of formaldehydes in indoor environments.</p> <![CDATA[PESTICIDE RESIDUES IN CONVENTIONALLY AND ORGANICALLY GROWN TOMATOES IN ESPÍRITO SANTO (BRAZIL)]]> <p>The aim of this study was to investigate the presence of acephate, carbaryl, carbendazim, chlorpyrifos, dichlorvos, fenpropathrin, methamidophos and permethrin in conventionally and organically grown tomatoes from Espírito Santo, Brazil, between May 2012 and April 2013. QuEChERS sample preparation was used and analysis was performed by LC-MS/MS and GC-MS. The method validation showed good linearity (R &gt; 0.99), precision (RSD &lt; 13%) and accuracy (89 - 123%), and the limits of quantification were below 0.01 mg kg<sup>-1</sup> for all pesticides. The pesticides acephate, carbaryl (0.23 mg kg<sup>-1</sup>; exceeding maximum residue levels), carbendazim, chlorpyriphos, dichlorvos, fenpropathrin (0.41 mg kg<sup>-1</sup>; exceeding maximum residue levels), methamidophos and permethrin (0.51 mg kg<sup>-1</sup>, exceeding maximum residue levels) were found in conventional tomatoes. In organic tomatoes, only one sample exhibited the presence of permethrin (0.21 mg kg<sup>-1</sup>). Considering that the pesticides found are toxic and carcinogenic, and given the high incidence of irregularities, it is important to implement government actions to ensure consumer safety.</p> <![CDATA[METROLOGICAL EVALUATION OF THE ANALYTICAL CURVE FOR DETERMINATION OF VERY LOW CONCENTRATIONS OF SULPHUR CONTENT IN DIESEL OIL S-10]]> <p>The increasing search for a reduction in air emissions has provided a challenging analytical scenario. This paper discusses metrologically, the best practices relating to analytical curves for the determination of very low concentrations of sulfur content in diesel S-10 by monochromatic wavelength dispersive X-ray fluorescence spectrometry (MWDXRF). For weighted linear regression, a new strategy to correlate the weights with the output variable is proposed, which is lacking in the literature. The analytical curve 0-500 mg kg<sup>-1</sup>, built in compliance with international standards, featured heteroscedastic behavior. The results showed that weighted linear regression is the most suitable choice for assessing concentrations at the beginning of an analytical curve, such as 10 mg kg<sup>-1</sup> (product specification limit) rather than simple linear regression which holds that the measured results must be closest to the centroid of the regression line. Finally, it was observed that, when a shorter analytical curve is built, it loses both in accuracy and in precision for very low concentrations, as compared to t simple and weighted linear regression.</p> <![CDATA[PROTOTYPING OF PHOTOCATALYTIC MICROREACTOR AND TESTING OF PHOTODEGRADATION OF ORGANIC DYE]]> <p>A photocatalytic microreactor is defined as a microfluidic device, which is integrated with a photocatalytic coating of TiO<sub>2</sub> deposited on the inner surface of microchannels. This device is capable of degradation of organic dye solution in water in a continuous flow under the action of ultraviolet light. The objectives of this work were to present a rapid and economically viable approach for the prototyping photocatalytic microfluidic devices and to evaluate their photodegradation capability for organic dyes by ultraviolet-visible spectrophotometry. Prototyping of polydimethylsiloxane PDMS/TiO<sub>2</sub>/glass microreactors includes several procedures such as mold preparation, microchannel confection on PDMS surface, deposition of TiO<sub>2</sub> on these microchannels, O<sub>2</sub> plasma treatment of PDMS/TiO<sub>2</sub> and glass surface for sealing these two parts. The efficiency of the photocatalytic microreactors was evaluated by fluxing two organic dye solutions, rhodamine B and methylene blue, with different flow rates of between 2 and 4 mL h<sup>-1</sup>. When the flow rate at 2 mL h<sup>-1</sup>was applied, discoloration of ~ 65% was achieved for both dye solutions, while PDMS/glass microchannels, without TiO<sub>2</sub> film, demonstrated much lower discoloration of between 24 and 42% for rhodamine B and methylene blue, respectively. This confirmed that TiO<sub>2</sub> was successfully deposited onto PDMS microchannels.</p> <![CDATA[THERMAL DEGRADATION OF TOCOPHEROL AND OXIDATION PRODUCTS IN DIFFERENT OLIVE OIL CLASSES USING UV-VIS SPECTROSCOPY AND MCR-ALS]]> <p>Extra virgin olive oil, virgin olive oil and mixed oil were analyzed by UV-Vis spectroscopy and Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS). When the oils were heated at high temperatures (frying), oxidation products were formed which were harmful to human health and antioxidants present were degraded. The aim of this study was to evaluate tocopherol (an antioxidant present in oils) and the behaviour of oxidation products in different olive oil classes. MCR-ALS results showed that degradation started at 70 ºC for extra virgin olive oil, while tocopherol concentration decreased and oxidation products increased starting at 40 ºC in virgin olive oil. In mixed oil, commercialized as a mixture of 85% soybean oil and 15% olive oil, tocopherol concentration started to decrease and oxidation products increase at 30 ºC. The results suggested that extra virgin olive oil offered more resistance to increasing temperatures, while virgin olive oil and mixed oil were less resistant.</p> <![CDATA[DRUG DEVELOPMENT BY MOLECULAR HYBRIDIZATION: A MEDICINAL CHEMISTRY PRACTICE CLASS USING PARACETAMOL AND SULFADIAZINE TABLETS AND THE VIRTUAL TOOL <italic>SciFinder</italic><sup>®</sup>]]> <p>Medicinal Chemistry is a multidisciplinary discipline and the discovery of new bioactive molecules is one of its objectives. Molecular Hybridization (MH) is a strategy of rational design of new prototypes, where the lead compound is produced through an adequate fusion of pharmacophoric sub-unities. Undergraduate laboratory experiments for Medicinal Chemistry education with a focus on MH are scarce. Therefore, the present paper describes a practice class for some undergraduate courses (Pharmacy, Chemistry and/or Chemical Engineering) involving drug development and MH that can be performed at low cost. In this work, alternative materials such as paracetamol and sulfadiazine tablets were used to engage student's attention and to contextualize important concepts of MH. The experiment describes the synthesis of a new compound involving the azo coupling between an aromatic amine (sulfadiazine) and a phenol (paracetamol) to show undergraduate students a practical example of MH. In this case, SciFinder<sup>®</sup> - a search website of the American Chemical Society - was also demonstrated and utilized as a search tool in the proposed experimental class.</p> <![CDATA[ACETANILIDE: SOLVENT-FREE GREEN SYNTHESIS]]> <p>We described herein a solvent-free synthesis of acetanilide developed in the context of green chemistry. The synthetic approach consisted of the reaction of aniline with acetic anhydride without additives, while using smaller amounts of reagents and water than previously described for this undergraduate experiment. The E Factor was 0.6 by experienced chemists and 0.9 by students.</p>