Resumo em Inglês:

Near infrared spectroscopy in-line monitoring and modelling of soybean oil methanolysis has been done using multivariate curve resolution alternating least squares (MCR-ALS) with correlation constraint. This constraint allows for quantitation of the methyl ester formed with little calibration effort and the MCR model provides additionally a general description (qualitative and quantitative) of the rest of components in the process. Due to the complexity of this process, which shows components with severe kinetic and spectral overlap, suitably designed multiset analysis strategies were adopted to improve the recovery of concentration profiles of the methyl ester. To assess the temperature and catalyst concentration effects on the kinetic reaction, five batches with different temperatures (20, 44 and 55 °C) and catalyst concentrations (0.75 and 1 m/m%) were produced. The concentration profiles of methyl ester obtained by MCR-ALS for each batch was the starting information used to develop a simplified kinetic model and calculate the activation energy.

Resumo em Inglês:

Through dereplication strategies using gas chromatography-mass spectrometry (GC-MS) and ultra fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS), the ethanol extract from Psycotria nemorosa leaves (Rubiaceae) showed to be composed of: cinnamic acid, dihydroactinidiolide, 4-hydroxy-β-ionone, phytol, isophytol, 4,8,12,16-tetramethylheptadecan-4-olide, lupeol, a mixture of α/β-amyrin, the keto and acetylated derivatives, besides stigmast-4-en-3-one, campesterol, stigmasterol and γ-sitosterol by GC-MS. Likewise, by UFLC-MS/MS, the main compounds identified were: butin, resveratrol, rutin, kaempferol 7-O-β-D-glucopyranoside, deacetylasperuloside, epiloganin, hordenine, strictosidine, N-methyl-1,2,3,4-tetrahydro-β-carboline and N-formyl-tryptamine. The antinociceptive activity of the crude extract ant its fractions was reported.

Resumo em Inglês:

A method using micellar precipitation process using cationic surfactant cetyltrimethyl ammonium bromide at ambient temperature was investigated for simultaneous determination of benzimidazoles coupled with high-performance liquid chromatography (HPLC) analysis. The studied benzimidazoles was selected as model compounds including thiabendazole, albendazole, mebendazole, and fenbendazole. The experimental parameters affected the extraction efficiency, including the kind and concentration of salt, pH, concentration of CTAB, volume of 1-octanol, and the centrifugation extraction time, was optimized. The optimum extraction condition: 0.030 mol L-1 CTAB, 10% (m/v) NaCl, pH 4.0, 300 µL 1-octanol and centrifugation time 10 min. Under optimum conditions, enrichment factors of between 60 and 90 fold were obtained, leading to lower limit of detection in the range of 0.5-0.7 µg L-1, depending on the analytes. The calibration range of the method was linear over the wide range of 0.5-1000 µg L-1, with correlation coefficients more than 0.999. Finally, the proposed method was successfully applied in the analysis of benzimidazoles in milk samples.

Resumo em Inglês:

This work has focused on the synthesis of three nanosystems composed of superparamagnetic iron oxide nanoparticles (SPIONs) coated either with a carboxylate platinum(IV) complex (PD = cis,cis,trans-[Pt(NH3)2Cl2(HOOCCH2CH2COO)(OH)]) or with platinum(II) complex functionalized dextrans (DexPt1 = [Pt(Dex-NH2)Cl3] and DexPt2 = [Pt(Dex-NH2)(NH3)2(H2O)]). All nanosystems have shown superparamagnetic behavior. Powder X-ray diffraction (XRD) has confirmed that the SPIONs were iron oxide phase and transmission electron microscopy (TEM) has shown average size of 6 nm (M6). Characterization of the nanosystems by inductively coupled plasma atomic emission spectroscopy (ICP AES) has revealed the presence of platinum on their surface (M6@PD, 0.54 mmol g-1 of Fe and M6@CA@DexPt1-2, 0.32-1.20 mmol g-1 of Fe); infrared spectroscopy (IR) and thermogravimetric and differential thermal analyses (TG-DTA) have confirmed the presence of dextran. Furthermore, the colloidal properties of these nanosystems (M6@PD and M6@CA@DexPt1-2) have been evaluated in water and in PBS buffer. Although M6@PD has shown good colloidal dispersion in water in the pH range of 2.0-8.0, the system underwent rapid agglomeration in PBS buffer. The M6@CA@DexPt1-2 nanosystems have exhibited improved colloidal behavior both in water and in PBS, where hydrodynamic sizes were kept below 100 nm over a large pH range (2.0-12.0). Furthermore, the latter systems have displayed isoelectric points below pH 5.0 and low surface charges at pH 7.0 (ζ-potential = -10 mV) and therefore PBS did not affect their colloidal stability.

Resumo em Inglês:

Comprehensive two-dimensional gas chromatography (GC×GC) was used in this work in order to reveal and identify minor compounds of several raw materials in biodiesel samples, which are not detected by conventional GC analysis. Multiway principal component analysis (MPCA) of the chromatographic profile allowed to identify compounds as C15:1n-3, C18:2n-6, C20:1n-6, C20:3n-3, C20:3n-6, C20:4n-6 C20:5n-3, C21:1n-6, C22:1n-9, C23:1n-9, C24:1n-9 multi-unsaturated which were useful tracers to discriminate between biodiesel samples. In this way, the separation power of GC×GC combined with the MPCA algorithm proved to be a valuable strategy for biodiesel samples classification, allowing identification and providing additional compounds of the commonly known as chemical profile of biodiesel samples.

Resumo em Inglês:

The influence of cashew nutshell liquid (CNSL) in the oxidative stability of biodiesels prepared from oils of soy, corn, canola and sunflower was studied using the Rancimat method. The induction periods at 110 ºC, without and with the addition of CNSL at concentrations of 0.1, 0.5 and 1.0% m/m, were determined and clearly show an important increase in the oxidative stability proportional to the concentration of the additive. For example, with the addition of 0.1% m/m CNSL, the induction period, in hours, increased from 5.7 to 8.5 (soy biodiesel), from 1.7 to 4.0 (sunflower), from 4.3 to 9.3 (corn) and from 6.9 to 12.8 (canola). The rate constants of the oxidation reactions in presence of CNSL were also determined and their respective values are (in h-1): 0.77 ± 0.08, 2.48 ± 0.46, 0.94 ± 0.08, 0.51 ± 0.11. The activation parameters (enthalpy, ∆H*, entropy, ∆S*, and free energy of activation, ∆G*) for the oxidation reactions were determined.

Resumo em Inglês:

Melonal is a relatively unexplored ingredient in the field of chemistry with excellent sensory properties. The synthesis and characterization of novel transition 3d metal complexes of copper(II), nickel(II), cobalt(II) and chromium(III) involving the Schiff base of melonal were explored to examine their biological activity. Characterization of the complexes was carried out using matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF), gas chromatography-mass spectrometry (GC-MS), thermogravimetric analysis (TGA), UV-Visible and infrared (IR) spectrophotometry. The antimicrobial studies were conducted against six bacterial strains and six fungi. The minimum inhibition concentration observed was compared against the standard antibiotic gentamycin and the anti-fungal drug amphotericin. The activity studies indicated that cobalt(II) complex exhibited activity better than standard drug amphotericin against Penicillium chrysogenum. Molecular docking study confirms the protein binding and supports the experimental finding. Binuclear cobalt(II) and chromium(III) bridging complexes of Schiff base ligand were obtained.

Resumo em Inglês:

New unsymmetric thioether Schiff base amine, 2-(2-aminoethylthio)-N-(thiophene-2-ylmethylene)aniline was prepared by reaction of 2-aminothiophenol with N-(2-bromoethyl)phthalimide and then by thiophene-2-carbaldehyde. Then, the phthalimide group converted to the amine by hydrazine hydrate. The new potentially pentadentate N3S2 donor unsymmetrical Schiff base ligand, 2-(2-(pyridine-2-ylmethyleneamino)ethylthio)-N-(thiophene-2-ylmethylene)aniline (L) was prepared via [1 + 1] condensation of pyridine-2-carbaldehyde with this amine. Manganese(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes of this ligand were prepared by adding metal salts to an ethanolic solution in this ligand. The thioether amine, ligand (L) and unsymmetric Schiff base complexes are characterized by the appropriate spectroscopic methods such as infrared (IR), UV-Vis, 1H nuclear magnetic resonance (NMR), 13C NMR studies, X-ray, microanalysis and mass spectrometry.

Resumo em Inglês:

The purpose of this study was to compare the performance of gas chromatographic with electron capture detector, pulsed flame photometric detector and mass spectrometry (GC-ECD, GC-PFPD and GC-MS) and UV-Vis spectrophotometric methods, based on acidic hydrolysis with tin(II) chloride of dithiocarbamate and analysis of the evolved CS2. For the validation studies were assessed linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy and precision. Recovery experiments were performed at 0.05 and 0.4 (chromatographic method) and 0.4, 0.8 and 2.0 mg CS2 kg-1 (UV-Vis spectrophotometric method). The analytical curves were linear from 0.08 to 2.0 µg CS2 mL-1 (chromatographic method) and from 0.4 to 2.2 µg mL-1 and from 2.2 to 8.9 µg CS2 mL-1 (both with r2 > 0.995) (UV-Vis spectrophotometric method). Method LODs were 0.01 and 0.28 mg CS2 kg-1 and LOQs were 0.02 and 0.4 mg CS2 kg-1 for the chromatographic and spectrophotometric methods, respectively. Acceptable accuracy was obtained for both methods (RSDs < 15.9% and recoveries from 87.7-107.4%). There was no significant difference between the techniques and detectors employees.

Resumo em Inglês:

Three new steroidal glycoalkaloids (SGA) were isolated from green berries of Solanum pseudoquina A. St.-Hil. The extract obtained after treatment with 5% acetic acid aqueous solution was subjected to several chromatographic procedures, leading to an enriched alkaloidal fraction. The enriched alkaloidal fraction was subjected to a semi preparative high performance liquid chromatography (HPLC) leading to the isolation of three new SGA from S. pseudoquina: 3-O-(β-D-glucopyranosyl) (20S,25S)-22,26-epimino-16α-acetyl-cholesta-22(N)-ene, 3-O-(β-D-glucopyranosyl) (20R,25ξ)-23,26-epimino-16α-acetyl-cholesta-5,23(N)-dien-22-one and 3-O-(β-D-glucopyranosyl) (20S,25ξ)-23,26-epimino-16α-acetyl-cholesta-5,23(N)-dien-22-one. The structures of the new compounds were elucidated with the help of 1D and 2D nuclear magnetic resonance (NMR) and infrared spectroscopy together with high resolution electrospray ionization and atmospheric pressure chemical ionization mass spectrometry.

Resumo em Inglês:

In this study, changes on the chemical composition and on the humic acids yield of coal matrices promoted by 25% HNO3 treatment were investigated, by means of elemental, thermogravimetric analyses, and Fourier transform infrared spectroscopy (FTIR). The "run of mine" (ROM) matrix C-MTR (ROM coal) showed the highest C content (41%), highest C/N ratio (76) and lowest ash content (54%) of the studied samples. In contrast, coal tailings presented a higher degree of aromaticity. Treatment with HNO3 solution increased N content, but not that of C. Therefore, the C/N ratio of all samples decreased to values between 11 and 20. The insertion of N occurred in the aromatic structures, while the oxidation occurred in both the aromatic and aliphatic chains. HNO3 treatment increased the humic substances content and the largest increase being observed in the coal tailings (16 to 31% increment in comparison to the untreated sample). The generated humic acids showed in general a chemical composition similar to that of soil humic acids, but a greater aromaticity degree.

Resumo em Inglês:

In this study the coagulation-flocculation process was evaluated as an alternative for treatment of biodiesel wastewater. The role of two coagulants, Al3+ and Fe3+, as well as its dosage, pH, treatment time, stirring and aeration were evaluated. It was observed that in the treatment using Al3+ the pH of the effluent (9.7) does not need to be adjusted, while for Fe3+ a previous adjustment to pH 5.0 was necessary. On the other hand, a high concentration of Al3+ (243 mg L-1) and a relatively long treatment time (70 min) were required to reach more than 96% of turbidity removal, when compared to the processing using Fe3+ (56 mg L-1 and 53 min), attributed to the formation of different mole fractions of hydrolyzed cationic species. Under the optimized conditions, more than 96% of turbidity, apparent color and suspended solids, and 82% of oil and fats were removed.

Resumo em Inglês:

An electrochemical sensor for H2O2 determination was prepared by electrodepositing copper oxide nanoparticles on the activated pencil graphite electrodes. At first, a study has been made of the optimum conditions for chemical activation of the pencil graphite electrodes (APGE) and then the activated pencil graphite electrode was modified with copper oxide nanoparticles (CuO/APGE) and used as a non-enzymatic hydrogen peroxide sensor. The morphology of the modified electrode surface was investigated by scanning electron microscopy (SEM). Upon the addition of H2O2, the modified electrode (CuO/APGE) exhibits significant oxidation of H2O2 with starting potential around +0.05 V (vs. Ag/AgCl) which dramatically decreases the overpotential of H2O2 oxidation. Under the optimal experiment conditions, the electrocatalytic response current of this sensor was proportional to the H2O2 concentration in the range of 5.0 × 10-6 to 1.6 × 10-3 mol L-1 with a detection limit down to 0.21 µmol L-1 (signal/noise = 3). The sensitivity was calculated to be 4.75 µAL mmol-1. The electrochemical active surface area and the catalytic rate constant of hydrogen peroxide electro-oxidation were calculated. The H2O2 sensor exhibited a low detection limit, a good signal reproducibility (relative standard deviation (RSD), n = 4) 2.36% and the accurate measurements in milk as the real sample.

Resumo em Inglês:

Amaryllidaceae alkaloids are well-known isoquinolines which have demonstrated a wide range of biological activities such as antiviral, anticancer, acetylcholinesterase inhibition, antimalarial, among others. Mass spectrometry (MS) studies based on capillary gas chromatography (CGC), paper spray (PS), and leaf spray (LS) ionization were carried out for alkaloid investigation of the native Brazilian species Hippeastrum aulicum, along with nuclear magnetic resonance (NMR) techniques. Thirty-one alkaloids were identified including the new compound haemanthamine N-oxide. The results from PS- and LS-MS techniques were consistent with those observed in CGC-MS analysis. To the best of our knowledge, it is the first study combining NMR, CGC-MS and the ambient ionization-mass spectrometry (PS- and LS-MS) on Amaryllidaceae plants.

Resumo em Inglês:

An easy and efficient sample preparation method was developed for the determination of natamycin residues in wine samples by solvent extraction and ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) analysis. After choosing acetonitrile as extraction solvent, an experimental design was carried out with different amounts of C18 and primary secondary amine (PSA) sorbents in order to optimize the clean-up step. Validation results were satisfactory, with recoveries from 77 to 95% and relative standard deviation (RSD) lower than 10% for the spike levels 5, 10 and 20 µg L-1. Method limit of detection (LOD) and quantification (LOQ) were 1.5 and 5.0 µg L-1, respectively. The validated method proved to be an excellent analytical tool, with a total analysis time of 3 min. The method was applied in 10 Brazilian wine samples and no residues of natamycin were detected.

Resumo em Inglês:

Essential and toxic metals were determined in eighteen samples of medicinal herbs from Poland, Lithuania and Serbia by means of laser-induced breakdown spectroscopy (LIBS) and inductively coupled plasma optical emission spectrometry (ICP OES). Calcium, K and Mg concentrations were obtained in % (m/m) and other metals (Na, Co, Cu, Fe, Mn, Ni, Zn, Cd, Cr and Pb) in mg kg-1. The fact that the herb samples analyzed belonged to specific plant species and represented different morphological plant parts explained the characteristic distribution in two-dimensional scores plots obtained by principal component analysis (PCA). A strong correlation of LIBS results was achieved in comparison to those obtained by ICP OES for Ca, K and Mg. Differences in the types of infusions were observed, in that leaves are related to Zn and Ni concentrations, leaves and flowers to Co, Ca and Mn concentrations and flowers to K, Na, Mg and Fe content.

Resumo em Inglês:

A set of eight tar sand samples with identical source, from sedimentary facies of the Pirambóia Formation, Paraná Basin, provides an interesting opportunity to assess the biodegradation extent of bitumens using high-resolution mass spectrometry with Orbitrap mass analyzer. The results suggest that acidic compounds have been degraded by microorganisms, since the O2 and O3 classes were lower to bitumens from dry interdune facies, the most biodegraded. It was also proposed a new parameter to evaluate biodegradation, DBE ratio (ratio between acidic species with the same number of double bond equivalent), that was used together with the already proposed A/C ratio (acyclic to cyclic naphthenic acids), both obtained from O2 class distribution. The bitumens from dry interdune facies presented the highest DBE ratios and lowest A/C ratios, which suggested that these parameters can be used to assess the extent of bitumen biodegradation in which the DBE ratios increase and the A/C ratios decrease with increasing biodegradation.

Resumo em Inglês:

Dioxins (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs)) are substances that represent a global concern due to their ubiquitous presence and toxicity. Industrial processes and other human activities as well as uncontrollable accidents are the main sources that release these pollutants into the environment. The presence of these compounds has been reported in soils from Europe, Asia and Africa, but currently, there is not much information of dioxin levels in soils from Brazil. This paper presents the levels of PCDD/Fs, dioxin-like PCBs (dl-PCBs) and non-dioxin-like PCBs (ndl-PCBs) in soils collected from urban areas of Belo Horizonte city, Minas Gerais State, Brazil. Total toxic equivalents (TEQ) observed ranged from 0.43 to 4.54 ng TEQ kg-1 d.m. The highest concentration TEQ found was 2.68 (± 1.63) ng TEQ kg-1 d.m. The low total TEQ achieved suggests that the locations evaluated are not being affected by possible sources of dioxin emissions, although Belo Horizonte is surrounded by a number of them.

Resumo em Inglês:

A feasible, rapid, sensitive and reliable dispersive liquid-liquid microextraction (DLLME) and ultrasonic assisted liquid-liquid microextraction (USAEME) combined with high-performance liquid chromatography (HPLC) method with UV detection was developed and validated for analysis of bosentan in human plasma and urine samples. All validation tests were reported according to FDA guidelines. Since chromatographic methods are precise, accurate and provide excellent separation are increasingly being used in determination of trace amount of drugs in biological goals. So the optimized experimental extraction factors from our previous work were used to evaluate HPLC-UV method for decreasing the limit of quantifications (LOQs) to cover the therapeutic range. Simple centrifugation of urine samples was sufficient prior to microextraction procedure, while acetonitrile protein precipitation provides sample clean up for plasma samples. The suggested method was linear (correlation coefficient R2 > 0.998) over a range of 0.1-10 µg mL-1 which covers the therapeutic range. Proposed methods are practical for quantitative analysis of bosentan in real samples, and could be used in routine clinical analyses.

Resumo em Inglês:

A fast and sensitive method using high performance liquid chromatography-fluorescence detection (HPLC-FD) and ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) was developed and validated for the determination of avermectins residues in ovine muscle samples. QuEChERS (quick, easy, cheap, effective, rugged and safe) sample preparation based on acetonitrile extraction followed by partitioning with NaCl and Na2SO4 and dispersive solid-phase extraction (d-SPE) clean-up with C18 was applied. Na2SO4 was used instead of MgSO4 due to lower amounts of co-extractives in the final extract. The procedure was validated according to the Commission Decision 2002/657/EC. The method showed determination coefficients (r2) higher than 0.99, recoveries between 93.2 and 124.3% for spike levels between 0.5 and 2.0 times the maximum residues limit (MRL) values. The repeatability and intermediate precision RSD values ranged from 1 to 19%. Decision limits (CCα) and detection capabilities (CCβ) ranged from 10.7 to 59.4 µg kg-1 and 11.4 to 68.8 µg kg-1, respectively. Method performance was successfully evaluated by analyzing real samples and proficiency test with a z-score in the range of ±1.

Resumo em Inglês:

A procedure has been developed for simultaneous separation/preconcentration of copper, nickel, and zinc based on in situ ionic liquid-based dispersive liquid-liquid microextraction method as a prior step to their determination by flame atomic absorption spectrometry. The analytes reacted with sodium diethyl dithiocarbamate at pH 7 to form hydrophobic chelates, which were separated and preconcentrated in the ionic liquid phase. The method is fast, simple, accurate, and environmentally friendly. The parameters affecting the extraction efficiency of the proposed method such as the pH of sample solution, centrifugation time, type and volume of the dispersive solvent, and the salt effect were studied. Enrichment factors of 61.8, 61.2, and 40.0 and detection limits of 0.79, 0.93, and 0.71 µg L-1 were obtained for copper, nickel, and zinc, respectively. The relative standard deviations based on six replicate measurements were between 1.0 and 2.7%. The method was successfully applied to the extraction and determination of these metals in wastewater and alloy samples.

Resumo em Inglês:

Dengue virus (DENV) has been characterized as having great clinical importance in the world, as there is no specific treatment against this virus. The NS2B-NS3pro complex is essential for the replication and maturation of DENV and is a potential pharmacological target. The present study aims to evaluate and understand the interactions and affinities (via molecular docking/AutoDock Vina) of 16 peptidomimetic derivatives applied to a NS2B-NS3pro DENV-2 complex constructed by homology modeling (via SWISS-MODEL). Two compounds were selected as potential inhibitors of this protein complex. In addition, these compounds possess important interactions involving Ser135, Gly169 and Tyr161, which have been described previously to be fundamental to the recognition of inhibitors directed to this receptor. Thus, the involvement of these residues is significant pharmacologically because they may contribute to the inhibitory action of this molecular target against DENV.

Resumo em Inglês:

Myracrodruon urundeuva Fr. Allem. (Anacardiaceae) is the scientific designation of "aroeira-do-sertão", a tree well dispersed through the "Caatinga", the characteristic northeastern Brazil flora. Its trunk bark decoction is used to treat cutaneous affections, urinary and respiratory diseases and as a postpartum aseptic bath. This work reports the analyses of the essential oils from leaves of 62 specimens of "aroeira-do-sertão". Analyses by 1H nuclear magnetic resonance (NMR) and gas chromatography coupled to mass spectrometry (GC-MS) of all oil samples permitted the characterization of all major components and, in consequence, the characterization of six different chemotypes of M. urundeuva, represented by the chemomarkers: myrcene, α-pinene, limonene, Δ3-carene, (Z) and (E)-β-ocimene.

Resumo em Inglês:

Synthetic fungicides are a common treatment for post-harvest diseases in fruits, although demand is increasing for alternatives such as biopesticides. The aim of this work was to investigate the presence of naturally occurring antifungal compounds in Brazilian specimens of the weed Conyza canadensis. Two compounds [(4Z)-lachnophyllum lactone and (4Z,8Z)-matricaria lactone] were isolated and their antifungal activities were evaluated against eight postharvest disease fungi. Aspergillus niger, Cladosporium sp., and Penicillium digitatum proved susceptible to the treatment (minimum inhibitory concentrations varying from 32 to 64 µg mL-1). These fungi are common postharvest pathogens of fruits and vegetables, causing rots and secreting mycotoxins. A green and sustainable extraction method employing pressurized hot water was developed and optimized (100 °C, 4 × 1 min cycles). Yields of 1.46 and 0.24 mg g-1 were obtained for (4Z)-lachnophyllum lactone and (4Z,8Z)-matricaria lactone, respectively. The extract could be applied directly to fruits and vegetables in postharvest treatments.

Resumo em Inglês:

The aim of this study was to quantitatively determine the olanzapine in a pharmaceutical formulation for assessing the potentiality of near infrared spectroscopy (NIR) combined with partial least squares (PLS) regression. The method was developed with samples based on a commercial formulation containing olanzapine and seven excipients. Laboratory and commercial samples (n = 27 and 18, respectively) were used by defining the calibration and prediction sets. The method was validated in the range from 1.0 to 12.5 of olanzapine per 100 mg of powder (average mass 210 mg), by accuracy, precision, linearity, analytical sensitivity, limit of detection and quantification. The multivariate model developed for olanzapine was based on PLS and the determination coefficient (rc and rp), with the root mean square error of calibration and prediction being 0.95, 0.93, 3.2 × 10-3 and 4.0 × 10-3% m/m, respectively. The proposed NIR method is an effective alternative for quantification of olanzapine in the pharmaceutical industry.