Resumo em Inglês:

In this review, we present the potential use of the heterocyclic oxadiazole rings in the design and synthesis of new drugs to treat parasitic infections. We intend to compare herein all the four isomeric forms of oxadiazole rings as well as discuss the differences and similarities between them. In addition, we discuss aspects on their reactivity that justify the great importance of both 1,2,4- and 1,3,4-oxadiazoles isomers when compared with their other two isomers. Although some oxadiazole isomers satisfy Hückel's rule, there are differences concerning their aromaticity, which have a great impact on the possible interactions of the oxadiazole ring with biological receptors. The set of works selected from the literature and discussed herein points out the oxadiazole core as an important and versatile scaffold in the development of new chemical entities potentially useful as antiparasitic drugs.

Resumo em Inglês:

A novel nanofibrous film chemosensor was designed and fabricated for detecting Fe3+. It displayed good sensitivity and selectivity as a sensing material for Fe3+. The addition of Fe3+ would induce obvious fluorescent quenching of the nanofibrous film and the other common metal ions did not interfere in the recognition of Fe3+. The detection limit for Fe3+ of this sensing material was calculated to be 10.63 μmol L-1. Moreover, the nanofibrous film could not only be regarded as a chemosensor for detecting Fe3+, but also as an adsorbent to remove Fe3+ with high efficiency in solution. The adsorption capacity was calculated to be 13.93 mg g-1 of Fe3+/nanofibrous film from Langmuir plot.

Resumo em Inglês:

In this study, the fatty acid (FA) composition of the Japanese grape (Hovenia dulcis) seed oil (JGSO) was firstly evaluated. It was found that the seed oil is rich in alpha-linolenic acid (LNA), containing approximately 425 mg LNA g-1 of total lipids. A fish diet supplemented with JGSO was prepared and supplied to Nile tilapia to investigate the FA composition of the fillets. For this, Nile tilapia were submitted to two feeding treatments: a control diet with 4.2% of soybean oil, and a diet supplemented with 4.2% of JGSO. The LNA, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) values increased significantly (406, 153 and 126%, respectively) with JGSO in the diet and with an increase in feeding time, while the nutritional quality indexes, n-6/n-3 ratio and index of thrombogenicity, decreased 2.8 and 1.4 times, respectively. Thus, the replacement JGSO in the diet raised the nutritional lipid quality in Nile tilapia.

Resumo em Inglês:

Mass spectrometry (MS) is a powerful technique that can provide the biochemical signature of a wide range of biological materials such as cells and biofluids. However, MS data usually has a large range of variables which may lead to difficulties in discriminatory analysis and may require high computational cost. In this paper, principal component analysis with linear discriminant analysis (PCA-LDA) and quadratic discriminant analysis (PCA-QDA) were applied for discrimination between healthy control and cancer samples (ovarian and prostate cancer) based on MS data sets. In addition, an identification of prostate cancer subtypes was performed. The results obtained herein were very satisfactory, especially for PCA-QDA. Selectivity and specificity were found in a range of 90-100%, being equal or superior to support vector machines (SVM)-based algorithms. These techniques provided reliable identification of cancer samples which may lead to fast and less-invasive clinical procedures.

Resumo em Inglês:

Phenolic compounds are important environmental contaminants due to their high toxicity and persistence in the environment. The use of enzyme-based electrochemical biosensors is a simple, sensitive and low-cost alternative for the determination of these pollutants in contaminated waters. However, in most cases, it is impossible to detect specific compounds in a mixture of phenols due to signal-overlap, as the instruments operate at very close potentials, given that the system is based on a single enzyme to detect similar structures. In order to overcome this problem, in the present work we have successfully used multivariate calibration with partial least squares (PLS) for the simultaneous determination of hydroquinone and guaiacol by a tyrosinase-based biosensor that was assembled using an enzyme extract from yam. The use of PLS allowed us to work with a large number of voltammograms, leading to a single mathematical model for the simultaneous determination of phenols of similar structure in real samples with concentration values of mmol L-1.

Resumo em Inglês:

This paper compares the dichromate method with the photoelectrochemical method (PeCOD), with regards to the influence of chloride and turbidity with chemical oxygen demand (COD) determination. Whereas the upper limits of chloride concentration are well established for both techniques, the influence of turbidity and the combined interference of underdosing chlorides and turbidity together have never been reported. When only potassium hydrogen phthalate or sorbitol were analyzed, the results show no significant difference in either method when 607 mg Cl- L-1 or 230 NTU of turbidity were added to the samples within the range of 100-900 mg L-1 COD. However, a combined effect of these two interferents leads to significantly different results, mainly for low COD range, as evidenced by the Student's t-test for paired samples (p = 0.05).

Resumo em Inglês:

During the period from June 2012 to June 2013, the concentrations and chemical composition of PM2.5 and PM2.5-10 (particulate matter with a diameter of 2.5 μm or less and between 2.5 and 10 μm, respectively) were monitored at four sampling points in the Rio de Janeiro metropolitan area, and two of the points were in close proximity to the 2016 Olympic Games facilities with a total of 122 samples at each sampling point. At all four sampling stations, the annual mean value of PM10 was above the World Health Organization (WHO) air quality guideline, although frequent violations of the 24 h guideline were observed at only two of the points, Duque de Caxias and Taquara. On the other hand, PM2.5 concentrations at the four sampling points met both the annual and 24 h WHO PM2.5 air quality guidelines. The vehicular contribution to PM2.5 ranged from 48 to 70%, with a mean value of 59 ± 9%. Considering that the Brazilian market already has fuel quality that is comparable to international standards (gasoline S50 and diesel S10), further air quality improvements are expected with investments in a public transport network, urban mobility programs and fleet renewal, which are considered a legacy of the 2016 Olympic Games.

Resumo em Inglês:

Termites are insects with a complex social organization on castes among which soldiers are the only responsible for the colony defense. The soldiers of the Nasutitermes genus use chemical defense, which comprises a mixture of mono, sesqui and mainly diterpenes. The new diterpene 2b,3a-dihydroxy-trinervita-1(15),11-diene, found in Nasutitermes macrocephalus, was isolated using preparative high performance liquid chromatography (HPLC) and identified by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) techniques. The absolute stereochemistry determined was supported by ab initio calculations and by comparison of the experimental circular dichroism data with the theoretical results. The isolated diterpene was evaluated against the bacteria Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), and the fungi Candida albicans and Aspergillus brasiliensis. The isolated diterpene presented minimal inhibitory concentrations of 62.5 and 62.5 µg mL-1 against S. aureus and C. albicans, respectively.

Resumo em Inglês:

This study investigates the mechanisms of interaction between benzophenone derivatives and cruzain and Llacys1 (the protein expressed by cysteine protease gene isoform 1 of L. amazonensis) by homology modelling, docking and molecular dynamics simulation. The results predict that the same binding site in cruzain and Llacys1 is involved in complexes with benzophenone derivatives that cause non-competitive inhibition of the enzymes. The Gln residue is conserved among the enzymes, and is shown to be a key residue in the allosteric site of these cysteine proteases and in the interaction with benzophenone derivatives. The binding free energies highlight that the main energetic term contributing to the cruzain- and Llacys1-benzophenone compound interactions is the van der Waals term. Experimental results showed that benzophenone derivatives are promising potential inhibitors of cysteine proteases. Moreover, we found that two benzophenone derivatives are the most effective inhibitors of cruzain and L. amazonensis cysteine protease.

Resumo em Inglês:

An optical sensing film was fabricated for sensitive determination of zinc ion in aqueous solutions. The optical sensor was prepared by synthesized ionophore, 5-Br salophen, dioctyl sebacate (DOS) as a plasticizer, sodium tetraphenyl borate (NaTPB) as a lipophilic anionic additive in a poly(vinyl chloride) membrane. The optode response is based on the cation-exchange membrane and indicated a significant absorbance signal change on the exposure to Britton-Robinson buffer solution of pH 5.7 containing Zn2+ ion. The proposed sensor showed a linear range of 4.9 × 10-5-4.5 × 10-12 mol L-1 with a limit of detection of 3.9 × 10-12 mol L-1. Furthermore, satisfactory analytical sensing characteristics including selectivity, stability, and reproducibility for the determination of zinc ion were obtained. The response time of the sensing film was less than 5 min, depending on the concentration of Zn2+ ions. The proposed sensor was successfully applied for determination of zinc in tap water, river water, and sea water.

Resumo em Inglês:

A selective, rapid and sensitive method using ultra-high performance liquid chromatography was developed and used for the simultaneous determination of kaempferide, kaempferol, and isorhamnetin in rat plasma after oral administration of Sedumsarmentosum Bunge extract. A 6430 triple-quadrupole tandem mass spectrometer in multiple reaction monitoring mode, with a negative electrospray ionization source, was used for the detection. A Waters Symmetry C18 column with isocratic elution (methanol:5 mM ammonium acetate at 75:25, v/v) was used for separation at a flow rate of 0.3 mL min-1. The method was linear for all analytes over the investigated concentration range (r > 0.9900). The intra- and inter-day precisions ranged between 3.88 and 7.74% and the accuracies ranged between 88.63 and 98.74%. The mean recoveries and matrix effect were higher than 85.66 and 92.36%, respectively. All the three compounds tested were stable during storage and analyses. The method was successfully applied to a pharmacokinetic study.

Resumo em Inglês:

In this work, we examined how photoluminescence in poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is affected by morphology, dictated by the mode of preparation. For that, MEH-PPV dilute solutions in good and non-solvents, thick cast films with poly[methylmethacrylate] (PMMA) as inert matrix and spin-coated thin films were prepared. These systems were studied by steady-state and time-dependent fluorescence spectroscopy and electronic microscopy. Unexpected photoluminescent behavior was detected in solutions and films and it was related to different excitons modulated by MEH-PPV conformation. By semi empirical calculations we obtained the singlet and triplet state energies of an MEH-PPV model system and, from time-resolved fluorescence spectroscopy, the existence of short-lived excited states was revealed, enabling us to infer on possible singlet fission in MEH-PPV-based systems.

Resumo em Inglês:

In this study, a novel electrospun nanofibrous composite was synthesized from polyacrylonitrile (PAN) and well-dispersed oxide nanoparticles containing Ti and Ag (PAN-TA). The nanoparticles incorporated into the nanofibers can endow the composite with photocatalytic and antimicrobial ability. The morphologies and structure of the nanofibers were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Controlled experiments were carried out with the effects of chemical modification, solution pH, temperature, dosage, contact time, and initial concentration of the dye. The methylene blue (MB) dye was completely removed within 20 min at room temperature 25 ºC with high maximum retention capacity of 155.4 mg g-1. Moreover, equilibrium data and kinetics data indicated that the dye adsorption agreed well with the Langmuir isotherm model and pseudo-second order model, respectively. In addition, the nanofibers could be easily separated from dye solution and showed high reusability for numerous repeat cycles, thus indicating good application prospects for the wastewater treatment.

Resumo em Inglês:

A method for chlorine determination in crude oil samples, through the formation of MgCl molecule, by high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) was developed and is described in this paper. The use of this molecule for chlorine determination in crude oil has not been reported up to now. Measures were carried out at the wavelength 377.010 nm and the samples were submitted to a simple treatment as emulsion, whose composition was optimized applying a simplex-centroid experimental design. Magnesium was used as molecule forming agent at the concentration of 10 g L-1, at least 500 times higher than the concentration of chlorine. This excess is required to ensure the molecule formation of all content of Cl present in the sample. Chemical modifier Pd was used and improved greatly the signal intensities. Optimized pyrolysis and vaporization temperatures, applied for determination, were 800 and 2300 °C, respectively. Accuracy was evaluated through analysis of certified reference materials, NIST 1848 and NIST 1634c, and addition and recovery tests with recoveries between 92 and 117%. Limits of detection and quantification were 3.0 and 9.0 µg g-1, respectively. The method was applied to eight crude oil samples.

Resumo em Inglês:

An ultrasound-assisted saponification (UAS) method for the determination of phytosterols (campesterol, β-sitosterol and stigmasterol) in passion fruit seed oil, followed by gas chromatography with flame ionization detection, was developed and validated. Under the optimum conditions, good linearity with correlation coefficients higher than 0.99 was obtained for all analytes. The recoveries for the proposed approach were between 103 and 107%, the limits of quantification were between 70 and 180 μg kg-1 and the precision values expressed in terms of relative standard deviations (RSD) were lower than 19%. The developed method was successfully applied to the analysis of passion fruit seed oil samples from different species, including yellow passion fruit, sweet granadilla and sweet passion fruit. In all species of analyzed passion fruit seed oils, β-sitosterol was found with the highest abundance, ranging from 0.90 ± 0.02 to 1.60 ± 0.01 mg g-1 of oil, followed by stigmasterol (0.70 ± 0.01 to 1.40 ± 0.12 mg g-1 of oil) and campesterol (0.10 ± 0.01 to 0.30 ± 0.06 mg g-1 of oil). Furthermore, the developed method proved to be a time-saving and efficient analytical procedure for the determination of phytosterols in oil samples.

Resumo em Inglês:

Lotus leaf is gaining growing popularity due to its various benefits and widely usage. In this paper, ten flavonoids in lotus leaf extract were analyzed by high performance liquid chromatography (HPLC). Centrifugal ultrafiltration combined liquid chromatography was used to screen alpha-amylase inhibitors from ten flavonoids mixture and the binding degrees ranged from 2.34 to 94.1%. The alpha-amylase inhibition and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) antioxidant activity of ten flavonoids were verified as well. Apigenin, kaempferol and isorhamnetin with relatively higher binding degrees showed higher inhibition on alpha-amylase as well. The interactions between these flavonoids and alpha-amylase were investigated by spectroscopic method. As a result, the fluorescence quenching could be considered as static quenching because the quenching rate constant (Kq) values were higher than 2.0 × 1010 L mol -1 s-1. The binding constants (log10 Ka) of ten flavonoids were in the range of 5.971 to 7.417 L mol-1. The hydrogenation of C2=C3 double bond of apigenin and quercetin decreased the affinity for alpha-amylase (1.92- and 2.82-fold). The hydroxylation on 3 and 3' position decreased the affinity for alpha-amylase. Moreover, the glycosylation with different sugar moiety improved in varying degrees of affinity. The hydrogen bond force might be important in the binding between alpha-amylase and flavonoids.

Resumo em Inglês:

In this study, Dy3+-doped LaNbO4 phosphors with a blue to white emission that can be tuned by varying the activator concentration were prepared by one-step spray pyrolysis process. According to the powder X-ray diffraction results, increasing Dy3+ concentration favored the tetragonal phase. Slight changes were observed in the recorded Raman spectra as a function of Dy3+ concentrations while SEM (scanning electron microscopy) micrographs presented similar profiles regardless the Dy3+ amount. Investigation of Dy3+ emission data in the visible range showed that rising the Dy3+ concentration progressively shifted the emission towards the white color. All samples presented a wide excitation range from 254 to 475 nm.

Resumo em Inglês:

A simple, fast and efficient method was developed for determination of six synthetic dyes (Tartrazine, Sunset Yellow, Amaranth, Ponceau 4R, Indigo Carmine and Brilliant Blue) in sports drinks using dispersive solid-phase extraction (d-SPE) with the polymeric sorbent Oasis® HLB. Sample preparation using d-SPE permitted to simplify the procedure and use less sorbent in comparison with SPE. The use of a syringe for the elution step make this easier and avoid the use of a manifold. High performance liquid chromatography with UV-Vis detection was employed for quantification. Recovery results, evaluated at 0.5; 1.0 and 1.5 mg L-1, were between 76 and 108% with relative standard deviation < 18%. The method limit of quantification was 0.5 mg L-1. The developed method was applied to the analysis of commercial sports drinks and the results indicated that all studied samples presented dye levels in conformity with the Brazilian legislation.

Resumo em Inglês:

In this study, the chemistry stability of hydroquinone (HQ) was evaluated according to its effects in redox properties and compared to kojic acid (KA). The HQ oxidation was more inhibited by N-acetylcysteine (NAC) than ascorbic acid (AA). These results were elucidated using theoretical methods at the DFT/B3LYP level of theory. All electronic parameters were related between antioxidant performance and highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), HOMO-LUMO value gap (GAP), ionization potential (IP), and phenol or enol bond dissociation energy (BDEOH) values. However, the interactions between HQ and NAC cannot be related by changing of these electronic parameters. Therefore the high calculated values for electron transfer can be associated to NAC due to polarizability or chelation properties of sulfur moiety.

Resumo em Inglês:

Acute lymphoblastic leukemia (ALL) is a fatal disorder in most cases and is the most common cancer in young patients. ALL features an uncontrolled proliferation and maturation arrest of lymphoid progenitor cells (lymphoblast) in the bone marrow. An increase of reactive species production occurs in ALL with an involvement of oxidative stress (OS) and cellular damage. However, there is a lack of information about variations in young patients. The biomarker widely used to measure the OS is the main product of lipid peroxidation, the malondialdehyde (MDA). This biomarker, when evaluated by a chromatographic method and the data analyzed by multivariate analysis with other biochemical parameters of ALL patient charts, shows the distinction of healthy and ALL patients, and a great correlation with the risk of disease.

Resumo em Inglês:

The continuous search for biologically active compound candidates pushes the pursuit of new substances produced by diverse organisms. Endophytic fungi are known as a promising source of metabolites with several biological activities. Based on the rich Amazonian biodiversity and the chemical potential of microbial sources, three Talaromyces strains, all major endophytes from their respective host plants, were studied aiming at the isolation of biologically active secondary metabolites. Through classical chromatographic approaches, 13 compounds were isolated from the antimicrobial extracts of the studied strains. From these, polyketides, steroids, anhydrides, and phenolic compounds were identified. Among them, two previously undescribed compounds were elucidated based on spectroscopic and spectrometric methods, a homodimer chromanone and a maleic anhydride methyl ester. The antimicrobial activity against a panel of pathogenic microorganisms from extracts, fractions, and isolated compounds was evaluated.

Resumo em Inglês:

Omega-3 fish oil supplements are widely consumed as source of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, presenting beneficial effects on human health. This study aimed to evaluate fifteen brands of omega-3 fish oil supplements available in Brazilian market in order to estimate the Brazilian reality regarding those supplements. Twelve fatty acids were quantified by gas chromatography with a flame ionization detector (GC-FID), and lipid profile were obtained via mass spectrometry fingerprinting using direct electrospray ionization mass spectrometry (ESI-MS) to assess the form in which fatty acids are present as well as the possible fraud existence. Among all analyzed samples, thirteen brands were revealed as EPA and DHA sources (90.2-440.3 and 77.8-302.3 mg g-1lipid, respectively) in triacylglycerols (TAG) or ethyl esters (EE) form. However, two brands were discovered with addition of large amounts of soybean oil, leading the final consumer to ingest this low-cost oil believing that they are consuming adequate doses of EPA and DHA.

Resumo em Inglês:

The synthesis of novel amino alcohol derivatives based on cardanol and glycerol were achieved in good yields and characterized by 1H and 13C NMR (nuclear magnetic resonance) and MS (mass spectrometry). In addition, we evaluated the in vitro antimicrobial activity against Gram-positive (Staphylococcus aureus, standard and clinical strains), Gram-negative (Escherichia coli) and M. tuberculosis bacterial strains. The bioassay results indicated that four compounds showed activity against S. aureus, including the clinical resistant strain, with MIC (minimum inhibitory concentration) ranging from 3.90 to 15.60 µg mL-1 and M. tuberculosis, with MIC90 (minimum inhibitory concentration required to inhibit the growth of 90% of organisms) ranging from 3.18 to 7.36 µg mL-1.

Resumo em Inglês:

This work reports results of a study carried out to optimize the preparation conditions of Cu2ZnSnS4 (CZTS) thin films grown by sequential deposition of Cu2SnS3 (CTS) and ZnS layers, where the Cu2SnS3 compound was grown using a novel procedure consisting of simultaneous precipitation of Cu2S and SnS2 performed by diffusion membrane assisted chemical bath deposition (CBD) technique. The precipitation across the diffusion membranes allows achieving moderate control of release of metal ions into the work solution favoring the heterogeneous growth mainly through an ion-ion mechanism. Through a parameters study, conditions were found to grow Cu2SnS3 thin films which were used as precursors for the formation of Cu2ZnSnS4 films. The formation of CZTS thin films grown in the Cu2ZnSnS4 phase was verified through measurements of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Solar cells with efficiencies of 4.9% were obtained using CZTS films prepared by membrane assisted CBD technique as absorber layer.

Resumo em Inglês:

For the detection of tetraciclines in feathers, muscle and liver, an internal protocol was designed for in-house validation of two methods, through high performance liquid chromatography with tandem mass spectrometric (HPLC-MS/MS) techniques. This protocol was based on the recommendation of the decision 2002/657/EC from the European Community as well as the food and drug administration (FDA) VICHGL49. Limit of detection (LOD) was set at 20 μg kg-1 and the limit of quantification (LOQ) ranged from 21.5 to 24.2, 21.2 to 21.6, and 25.0 to 27.7 μg kg-1 in feahers, muscle and liver samples, respectively, for all analytes. The calibrations curves show a coefficient of determination (R2) above 0.98, 0.99 and 0.96 for feathers, muscle and liver samples, respectively. Analyte recovery ranged from 92 to 108%. In conclusion, these methods can be deemed accurate and reliable, and their validation is a fundamental step to be performed in depletion studies on these matrices.