Resumo em Inglês:

Site selectivity, regioselectivity and stereoselectivity of [2 + 3] cycloaddition of 4-trifluoromethylbenzonitrile oxide to polyunsaturated medium size rings including 1,5,9-cyclododecatriene, 11-membered sesquiterpenes, 1,3-cyclooctadiene and 5-vinyl-2-norbornene were examined. Site selectivity was correlated with electron charges of alkenyl carbon atoms. Structure of the products has been established by an extensive application of 1D and 2D 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and electrospray ionization mass spectrometry. Some of the obtained products showed moderate fungicidal activities.

Resumo em Inglês:

The correct selection of a dye that has effective action as a photosensitizer is a primary concern for successful therapeutic outcomes. The effectiveness of the photodynamic agent is related to both the targeting of cell membranes and the photochemical yield of the chosen dye. The distributions of xanthene derivatives Eosin Y, Erythrosin B, and Rose Bengal B in vesicles of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in both liquid-crystalline and gel phases were investigated by fluorescence spectroscopy. Binding constants, fluorescence anisotropy, fluorescence quenching, fluorescence quantum yield, and fluorescence resonance energy transfer at physiological pH conditions were determined. To Erythrosin B and Eosin Y, the iodide quenching rate constant was shown to involve a sphere of action mechanism driven by a specific interaction between Erythrosin B and Eosin Y molecules and the choline head-group of the phospholipid; in contrast, Rose Bengal B was located deep in the membrane and this mechanism was not present. The dyes can be ordered by their penetration depth in the membrane, and this order was found to be Eosin Y < Erythrosin B < Rose Bengal B. These results demonstrate a rational approach for the screening of more active agents for photodynamic therapy based on the affinity between the xanthene derivatives and DPPC vesicles.

Resumo em Inglês:

The development of drug delivery systems for photodynamic therapy (PDT) is increasingly demanded due to the hydrophobicity presented by most of photosensitizers molecules. Bacterial cellulose (BC), a highly pure cellulose produced by bacteria, possesses the essential features for applications in drug delivery systems, such as large surface area and excellent loading capacity. BC membranes prepared containing a photosensitizer, chloroaluminum phthalocyanine (ClAlPc), were tested aiming applications as a drug delivery system for PDT skin cancer protocols. BC membranes production was optimized regarding thickness and optical transmission. Thinner membranes lead to higher relative incorporation efficiencies. Skin permeation and retention in vitro tests were performed by using pig's ears as a skin model. ClAlPc was retained at stratum corneum and epidermis/dermis, showing adequate properties for topical administration of ClAlPc. Photophysical studies showed that singlet oxygen production was not affected for ClAlPc compartmentalized in the BC array. BC-ClAlPc membranes did not present cytotoxic effects in vitro.

Resumo em Inglês:

A label-free optical immunosensor was developed based on surface plasmon resonance (SPR) method for rapid and selective detection of Brucella melitensis. This immunosensor was constructed by immobilizing capture antibody on 11-mercaptoundecanoic acid modified gold disk. This fabricated immunosensor detected B. melitensis at a concentration range from 103 to 107 cell mL-1 (R2 = 0.998) and a detection limit of 100 cell mL-1. Additionally, the kinetic equilibrium dissociation constant (KD) for assessment of the interaction affinity was calculated as 1.1 × 10-9 mol L-1 that can be considered as high affinity interaction. This SPR immunosensor provided advantages in term of fast response, label free and accurate detection of B. melitensis in analytical systems.

Resumo em Inglês:

Radiolabelled peptides have attracted a great deal of attention due to their wide applicability in the development of target-specific radiopharmaceuticals. They can easily be used in diagnostic imaging as carriers for the delivery of radionuclides to tumors as well as for therapy. Previous investigations revealed that technetium(V) could form stable complexes with peptide-based ligands of N3S type such as Cys-Gly-Gly-Gly. Herein, a targeting HER-2 receptor peptide was labeled with technetium-99m (99mTc) with two different types of tetrapeptide-based ligands, Cys-Gly-Gly-Gly and Cys-Ser-Ser-Ser. The effect of experimental parameters in the labeling procedure such as type of buffer solutions, pH of media, and type of exchange ligands were optimized toward obtaining maximum labeling yield. The optimum labeling conditions were different for two peptides. Shelf life of both labeled peptides was determined by analytical reversed-phase high-performance liquid chromatography (RP-HPLC) and thin layer chromatography (TLC) that showed radiochemical yield up to 95% even after 4 h.

Resumo em Inglês:

The choice of an appropriate background electrolyte (BGE) and its components for capillary electrophoresis analysis is the main step in capillary electrophoresis method development. The use of an inadequate co-ion component could lead to asymmetrical peaks and selecting an inappropriate counter-ion could affect the buffer capacity and the pH of the BGE, leading to unreliable analysis. In this paper, we describe a systematic procedure for the development of a capillary electrophoresis method, based on the effect of varying pH on the ion effective mobility, to optimize the BGE composition. The method was applied to the separation of L-ascorbic acid in different samples. The optimized background electrolyte composition was 40 mmol L-1 tris(hydroxymethyl)aminomethane and 20 mmol L-1 2-morpholinoethanesulfonic acid, at pH 8.1. Sorbic acid was used as the internal standard and separation was carried out in a fused-silica capillary (32 cm total length and 8.5 cm effective length, 50 µm inner diameter), with a short-end-injection configuration and direct ultraviolet (UV) detection at 266 nm. The separation was performed in 26 s. The method shows good linearity (R2 > 0.999), excellent values for inter-day and intra-day precision and good recovery (in the range of 94-107%). The values obtained for limit of detection (LOD) and limit of quantification (LOQ) were 0.14 and 41 mg L-1, respectively. The systematic procedure applied shows to be a very useful tool for the first step method development for capillary electrophoresis.

Resumo em Inglês:

Researchers have developed new catalysts for fuel cells (FC), whose performances are compared after applying different normalization procedures. However, there is not a standard procedure. The current produced from CO electrooxidation was compared for Pt4Ru5Sn1/C and homemade Pt/C nanoparticles (NPs) normalized by different methods and the use of different methods renders different interpretations. Since the whole field aims to maximize the cost-effectiveness, a complementary method to normalize currents and power in terms of the total cost of the nanocatalyst, the Catalyst-based Cost method (CbC), was proposed. CbC considers the cost of all metals employed to build the catalyst, not only those ones with available surfaces. By applying a simple smoothing method on the prices in a time series, we were able to forecast the prices and consequently the power density of a FC. CbC provides tools for industrials forecast the designing of nanomaterials with improved efficiency and low cost.

Resumo em Inglês:

Three new unsymmetrical pyridine-containing diarylethenes with a variable peripheral heteroaryl unit were synthesized and their structures were determined by single-crystal X-ray diffraction analysis. The substituent effects of variable heteroaryl groups on the photochromic and fluorescence properties were systematically discussed. Thienyl and thiazyl could effectively enhance the cyclization quantum yields and photoconversion ratios in the photostationary state, as compared to the phenyl group. However, they had no obvious effect on the fluorescence behaviors. Moreover, X-ray structural analysis revealed that the N···S heteroatom-contact interactions resulted in a higher cyclization quantum yield, which may be ascribed to the effective stabilizing ability on the photoreactive formations in diarylethenes with a thienyl/thiazyl unit.

Resumo em Inglês:

The manuscript describes design and synthesis of novel oxadiazolyl-2-oxoindolinylidene propane hydrazides as amide tethered hybrids of indole and oxadiazole and their evaluation for anti-inflammatory and analgesic activity. The compounds were synthesized following five step reaction to yield fifteen derivatives as 3-(5-substituted-1,3,4-oxadiazol-2-yl)-N'-[2-oxo-1,2-dihydro-3H-indol-3-ylidene]propane hydrazides. The final derivatives 3-[5-(4-hydroxyphenyl)-1,3,4-oxadiazol-2-yl]-N'-[2-oxo-1,2-dihydro-3H-indol-3-ylidene]propane hydrazide and 3-[5-(4-methylphenyl)-1,3,4-oxadiazol-2-yl]-N'-[2-oxo-1,2-dihydro-3H-indol-3-ylidene]propane hydrazide were found to be highly promising molecules with severity index of 0.35 and 0.56, respectively, which is promising for an analgesic compound. The hydroxy and methyl substitution on phenyl ring system provided with active anti-inflammatory compounds having increase in reaction time of 84.11 and 83.17%, respectively compared to standard drug at 85.84%. Molecular docking studies exhibit comparable interaction with synthesized derivatives and standard drug having a dock score of -4.44 by the K-nearest neighbour genetic algorithm method.

Resumo em Inglês:

The Mn2+ and Mg2+ (or Zn2+) co-doped Li2Fe0.8-xMn0.2MxSiO4 (x = 0.05 and 0.1) are synthesized by a solid-state reaction route. Compared with the single doped Li2Fe0.8Mn0.2SiO4, the co-doped samples show improved cycling performance. The capacity retention can stay above 50% after 50 cycles, which is significantly higher than 30.4% for Li2Fe0.8Mn0.2SiO4. This phenomenon could be attributed to the increased structural stability caused by the incorporation of the electrochemically inactive M2+ ions. However, except for Li2Fe0.75Mn0.2Mg0.05SiO4, the other samples show decreased capacities, especially in the case of the Mn/Zn co-doping. Further tests indicate that the promotion of Li+ diffusivity may be a key reason for the improved rate and cycling performances. By contrast, the incorporation of Zn2+ impaired the cell performances such as increased internal polarization, hindered charge transfer, decreased Li+ diffusivity. In this work, the Mg2+ with smaller radius seems to be a better choice as the co-doping element at Fe sites than Zn2+.

Resumo em Inglês:

This study deals with B, S, and P determination in mineral fertilizer and S in commercial sulfur-formulation using inductively coupled plasma optical emission spectrometry. According to multivariate optimization using a Doehlert matrix, the analytes extraction in fertlizer can be conducted in open flask and heating on hot plate or in closed flask in microwave oven. However, when S is present in its elemental form in the fertilizer, the sample must be decomposed in closed flask in microwave oven for accurate S quantification. The uncertainties of the method were estimated according to the bottom-up approach, which were 7.1, 4.3, and 7.8% for B, S and P, respectively. The main sources of uncertainty identified were the intermediate precision, accuracy, regression of the calibration curve and errors originated from volumetric flasks and pipettes. Satisfactory results were obtained in the analysis of certified reference materials and sample from inter-laboratory programs as well as S recovery in a commercial elemental sulfur sample.

Resumo em Inglês:

Coal fly ash has been proposed as an alternative raw material for zeolite synthesis, however, the mobilization of toxic elements of this material into zeolite products, washing water and effluent is rarely addressed. In this study, Brazilian coal fly ash was used in the integrated synthesis (two steps) of zeolites Na-P1 and 4A and the distribution of approximately 40 major, minor and trace elements was investigated in all the input and output flows involved in the process. The mobilization of several elements was observed in the zeolite products, a number of which are highly toxic, such as As, Cd, Cr, Ni and Pb. With regard to the amount present in the ash, both zeolites were enriched in several elements, such as Ni in zeolite Na-P1 and As in zeolite 4A. The latter exhibited high purity, with most of the elements investigated having concentrations close to those measured in commercial zeolite 4A. Important information was gathered regarding zeolite synthesis using fly ash, which will ensure safer application of these materials and, if necessary, propose a contaminant-free synthesis route.

Resumo em Inglês:

We present here our results on the temperature controlled, selective hydrochalcogenation of 1,4-diorganyl-1,3-butadiynes with nucleophilic species of selenium, tellurium and sulfur generated in situ from the respective diaryl dichalcogenide and NaBH4. Using polyethylene glycol (PEG)-400 at 30 ºC the (Z)-chalcogenoenynes are obtained and at 90 ºC the (Z,Z)-bis-chalcogen-1,3-butadienes are produced in good to excellent yields. Alternatively to conventional oil bath heating, the use of microwave irradiation is also presented as an alternative energy source that provides the expected products in few minutes.

Resumo em Inglês:

In the past seven years, the SMD (Solvent Model Density) method has been widely used by computational chemists. Thus, assessment on the reliability of this model for modeling chemical process in solution is worthwhile. In this report, it was investigated six anion-molecule nucleophilic substitution reactions in methanol and dipolar aprotic solvents. Geometry optimizations have been done at SMD/X3LYP level and single point energy calculations at CCSD(T)/TZVPP + diff level. Our results have indicated that the SMD model is not adequate for dipolar aprotic solvents, with a root of mean squared (RMS) error of 5.6 kcal mol-1, while the Polarizable Continuum Model (PCM) method with the Pliego and Riveros atomic cavities has led to RMS error of only 3.2 kcal mol-1. For methanol solvent, the SMD method has a RMS error of 3.0 kcal mol-1. The classical protic to dipolar aprotic solvent rate acceleration effect was not predicted by the SMD model for the tested systems.

Resumo em Inglês:

The effect of γ-Al2O3 support on the NO adsorption on Pd4 clusters was investigated by means of density functional theory (DFT) calculations. Pd4 adsorbed on γ-Al2O3 (represented by a Al14O24H6 cluster) changes its preferential geometry from tetrahedral to a distorted planar structure. The alumina support promotes a higher dispersion in the palladium catalyst and reduces the NO adsorption energy to -25.6 kcal mol-1 (computed at B3LYP/LANL2DZ/6-311+G(d)), in close agreement with the experimental value of -27.2 kcal mol-1. On the bare planar Pd4 cluster the NO molecule adsorbs in a bridge arrangement, with adsorption energy of -41.2 kcal mol-1. Adsorption on the tetrahedral Pd4 cluster occur preferentially in an atop mode, with adsorption energy of -30.6 kcal mol-1. Charge density analysis show that the electron flux between the NO molecule and Pd4 depends on the adsorption form, with back-donation being stronger in the bridge adsorption mode.

Resumo em Inglês:

A Monte Carlo method is used in addition to functional and individual weighting to overcome multicollinearity problems in multiple linear regression equations applied as quantitative-structure-property-relationships, allowing the estimation of correct coefficient confidence intervals. The method was applied to rate constants for the Menschutkin reaction between Et3N and EtI in mono- and di-alcohols, at 25.00 ºC. Results show that the use of our methodology produces a significant improvement upon confidence interval estimates regardless of the level of collinearity present. Addition of weighting shows additional advantages, increasing the overall consistency of the regression process.

Resumo em Inglês:

In the present work, an inductively coupled plasma-tandem mass spectrometer (ICP-MS/MS) operating in single quadrupole and mass shift modes were evaluated for As determination in mineral fertilizers and agricultural gypsum with high contents of rare earth elements. For MS/MS mode, oxygen was the gas introduced into the octopole reaction system (ORS3). Samples were prepared by microwave-assisted digestion with diluted nitric acid solution. The accuracy was checked by analysis of a fertilizer certified reference material (NIST SRM 695) and by addition and recovery experiments. When operating in single quadrupole mode, recoveries ranged from 59 to 151%; while values obtained by MS/MS mode varied from 81 to 105% when 0.30 mL min-1 O2 was introduced into the ORS3. Limits of detection for As+ in single quadrupole and AsO+ in MS/MS mass shift mode were 6 and 9 ng L-1, respectively.

Resumo em Inglês:

A new titanium catalyst easily synthesized from ethylmaltol bidentate chelator ligand was studied in homogeneous and heterogeneous ethylene polymerization. The dichlorobis(3-hydroxy-2-ethyl-4-pyrone)titanium(IV) complex was characterized by 1H and 13C NMR (nuclear magnetic resonance), UV-Vis and elemental analysis. Theoretical study by density functional theory (DFT) showed that the complex chlorines exhibit cis configuration, which is important for the activity in olefin polymerization. The complex was supported by two methods, direct impregnation or methylaluminoxane (MAO) pre-treatment, in five mesoporous supports: MCM-41 (micro and nano), SBA-15 and also the corresponding modified Al species. All the catalytic systems were active in ethylene polymerization and the catalytic activity was strongly influenced by the method of immobilization of the catalyst and the type of support.

Resumo em Inglês:

This work describes a green approach to the synthesis of iron nanoparticles supported in silica using tea extract of the South American plant yerba mate (Ilex paraguariensis). Catalysts with different iron contents were obtained according to the reaction conditions employed. Characterization by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) revealed the amorphous nature of the nanoparticles, tentatively ascribed to iron(II)/iron(III) oxide composites, as Fourier transform infrared (FTIR) and thermogravimetric analyses confirmed their functionalization by the tea polyphenolic compounds. For the sake of comparison, crystalline zero-valent iron nanoparticles were prepared by the classical method using NaBH4. Both materials were tested in the degradation of methyl orange and led to complete decolourization; the green nanoparticles were very active as heterogeneous Fenton-like catalysts in presence of hydrogen peroxide, while the nanoparticles prepared with NaBH4 were efficient in the reductive degradation of the dye.

Resumo em Inglês:

In this work, the synthesized Fe3O4 nanoparticles was coated by sodium dodecyl sulfate and then it was used as a sorbent in mixed-hemimicelle solid phase extraction of some amphetamines, as psychoactive drugs, from biological samples. This extraction method was combined with dispersive liquid-liquid microextraction to enhance enrichment factors of targeted analytes. Effect of different parameters influencing the hybrid extraction performance, such as sodium dodecyl sulfate amount and sample pH, were investigated. The method showed linearity in the range of 1.0-250 and 2.0-250 µg L-1 for the most of analytes in urine and plasma samples, respectively. The limits of detection, based on signal to noise of 3, were found 0.1-0.2 and 0.3-0.5 µg L-1 in urine and plasma samples, respectively. The results of the intra-day and inter-day precision were less than 13.5% for all amphetamines. The amounts of relative recoveries in spiked urine and plasma samples were found in the range of 90-96 and 87-93%, respectively.

Resumo em Inglês:

In the present work, a novel, simple, and efficient method for the determination of silver in natural water samples was developed. The method is based on the extraction of silver with coacervate made up of decanoic acid reverse micelles and the subsequent determination by flame atomic absorption spectrometry (FAAS). Dithizone was used as a chelating agent. To obtain the best extraction results, some experimental parameters (such as coacervate composition, pH, concentration of chelating agent, and ionic strength) affecting the extraction efficiency were investigated and optimized. Under optimum conditions, the calibration curve was linear in the concentration range of 5-200 µg L-1, with the correlation coefficient (r) equal to 0.995. The limit of detection and the enrichment factor were 1.6 µg L-1 and 15, respectively. The method was successfully applied to the analysis of silver in natural water samples.

Resumo em Inglês:

Radix et Rhizoma Rhei has been recognized for centuries in traditional medicine for its multiple pharmacological actions. The free anthraquinones including physcion, chrysophanol, emodin, rhein, and aloe-emodin are the main bioactive components in Radix et Rhizoma Rhei. In the present study, a fast quantitative 1H nuclear magnetic resonance (q-HNMR) method for the determination and quantitation of five free anthraquinones in Radix et Rhizoma Rhei was developed. Validation of the quantitative method was performed in terms of specificity, accuracy, precision, and stability. The results showed that the solvent acetone-d6 enabled satisfactory separation of the signals to be integrated. Five anthraquinones in Radix et Rhizoma Rhei could be quantified accurately using featured signals from 1H NMR. This work implied that q-HNMR represents a feasible alternative to high-performance liquid chromatography (HPLC)-based methods for quantitation of anthraquinones in Radix et Rhizoma Rhei and is suitable for the quality control of Radix et Rhizoma Rhei.

Resumo em Inglês:

Hydroxynaphthoquinones such as lawsone (2-hydroxy-1,4-naphthoquinone) have proven to be effective antifungal agents. These compounds were tested for antifungal activity against yeast standard and clinical strains by the broth microdilution method. Among the synthetic lawsone derivatives, 2-hydroxy-3-((2-hydroxyphenyl)(pyrrolidin-1-yl)methyl)naphthalene-1,4-dione, 2-hydroxy-3-(((4-nitrophenyl)amino)(phenyl)methyl)naphthalene-1,4-dione and 2-hydroxy-3-((2-hydroxyphenyl)((4-nitrophenyl)amino)methyl)naphthalene-1,4-dione showed high activity against Candida albicans ATCC 10231, with minimal inhibitory concentrations (MICs) and minimal fungicidal concentrations (MFCs) ranging from 20 to 330 and from 80 to 330 µg mL-1, respectively. Moreover, they also showed a mechanism of action on exogenous ergosterol. Therapeutic concentrations (CC50) of 2-hydroxy-3-((2-hydroxyphenyl)(pyrrolidin-1-yl)methyl)naphthalene-1,4-dione, 2-hydroxy-3-(((4-nitrophenyl)amino)(phenyl)methyl)naphthalene-1,4-dione and 2-hydroxy-3-((2-hydroxyphenyl)((4-nitrophenyl)amino)methyl)naphthalene-1,4-dione were 52.81, 52.58 and 85.94 µg mL-1, respectively, which can be considered moderate or low. In addition, docking studies showed that these compounds had similar binding energy to standard ketoconazole, which are recognized as the molecular target by van der Waals interactions. Furthermore, they are under Lipinski's rule of 5 with a druglikeness score better than ketoconazole and nystatin. These findings suggest that 2-hydroxy-3-((2-hydroxyphenyl)(pyrrolidin-1-yl)methyl)naphthalene-1,4-dione, 2-hydroxy-3-(((4-nitrophenyl)amino)(phenyl)methyl)naphthalene-1,4-dione and 2-hydroxy-3-((2-hydroxyphenyl)((4-nitrophenyl)amino)methyl)naphthalene-1,4-dione have potential as leading compounds against human fungal infections.

Resumo em Inglês:

Illicit substances found in blotter papers and tablets seized by police are traditionally identified and characterized from extracts of these materials. However, the procedures involved in extraction stages can result in artifacts and even contamination of the samples to be analyzed. On the other hand, high-resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR) is a technique that requires no pretreatment steps, enabling direct analysis of the material, including the analysis of new illegal synthetic psychoactive substances. This study presents and discusses applications of the HR-MAS NMR in the analysis of tablets and blotter papers seized. Additional analysis in solution of the extracts of these materials was performed to compare the obtained spectral resolution signals. The results demonstrated that the HR-MAS NMR allowed the rapid identification of 3,4-methylenedioxy-N-methylcathinone (methylone), 4-methylmethcathinone (mephedrone), 2,5-dimethoxy-4-bromoamphetamine (DOB) and 2-(4-bromo-2,5-dimethoxyphenyl)-N-[(2-methoxyphenyl)methyl]ethanamine (25B-NBOMe) in samples of tablets and blotter papers seized in Goiás State, Brazil.

Resumo em Inglês:

Bark of acuri and endocarp of baru are residues generated during the processing of these fruits. One alternative to consider is the pyrolysis of these materials to generate bio-oils, opening the perspective for the production of environment-friendly, added value products. Samples of acuri and baru were subjected to laboratorial scale pyrolysis. At the optimized pyrolysis conditions, the bio-oils yields (m/m) were 30% for bark of acuri and 29% for endocarp of baru. Next, the obtained bio-oil was submitted to proximate analysis and GC×GC-TOF/MS (two-dimensional gas chromatography with time-of-flight mass spectrometric detection). The bio-oil generated from the bark of acuri proved to be of the highest complexity with 113 identified compounds, while the bio-oil generated from the endocarp of baru sample led to 71 identified compounds. A total of 29 compounds were confirmed using standards in the acuri bark bio-oil, while 23 compounds were confirmed for endocarp of baru bio-oil. There was a predominance of phenols and ketones for the bio-oil generated from acuri bark, and hydrocarbons and phenols for the bio-oil from baru endocarp.