Resumo em Inglês:

Civilian defense devices are physical and chemical artefacts used to incapacitate an aggressor without causing death or injury. As city violence increases, safety feelings became worst and a growing commercial demand for these materials supply faces technologically challenges not only to riot control but also to self-protection. Controversies on the use of these devices have been discussed, especially on their toxicity when synthetic chemical agents are used. Natural metabolites are a less explored alternative to meet this demand. They have the capacity to generate a temporary disabling effect due to their pungency. Those metabolites, which include capsaicinoids, gingerols and piperine, can be used as deterrent agents in civilian defense devices due to their low toxicity to humans. Although they are a viable alternative, there are few studies focused on their quality control, efficiency and toxicity. This review aimed to present relevant aspects about the development and use of natural products as deterrent agents in self-defense devices against aggressors and animals, and as non-lethal weapons for riot control in order to help the scientific development of this type of bioproduct.

Resumo em Inglês:

This study provides a fast, accurate and reproducible method for L-ascorbic acid (L-AA) determination in milk samples by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). A small volume of a low toxicity organic solvent (ethanol) was used for degreasing and deproteinization steps. Ethylenediaminetetraacetic acid disodium salt (EDTA) and formic acid were used as stabilizing agents. The method was successfully validated in terms of linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy, and inter/intra-day precision and applied in raw and processed milk samples. Good linearity (r2 > 0.9915) and low LOD and LOQ, 1.5 and 5.0 µg L-1, respectively, were obtained. The recoveries for 500 and 1000 µg L-1 spikes were higher than 90% and the precision values expressed in terms of relative standard deviation (RSD) were ≤ 6.8%. For the first time, the determination of L-AA in a 500 µg L-1 concentration range was reported for milk samples.

Resumo em Inglês:

A complete and unambiguous assignment of 1H and 13C nuclear magnetic resonance (NMR) signals of 29 naphthoquinones is reported on the basis of one- and two-dimensional NMR techniques (1H, 13C, 1H-1H correlated spectroscopy (COSY) and 1H-13C heteronuclear multiple-bond correlation (HMBC)). This is the first report distinguishing data between para-naphthoquinones, ortho- and para-furanonaphthoquinones isomers.

Resumo em Inglês:

Methasterone is a designer anabolic steroid that is prohibited for athletes and is monitored by anti-doping laboratories. In this work, our objective is to discover new human phase I metabolites, define their excretion kinetics for 30 days and analyze their phase II metabolism (sulfate, cysteine and N-acetylcysteine conjugates). Urine samples from four volunteers were analyzed by chromatographic techniques. Through gas chromatography coupled to mass spectrometry analysis it was possible to detect methasterone and its nine phase I metabolites in the urine samples after glucuronide enzymatic hydrolysis, from which one were previously unreported. These nine compounds were not excreted in free form. The new proposed metabolite is 17β-hydroxy-2α,17α-dimethyl-5β-androstan-3-one, obtained from the epimerization at C5. The 3α-hydroxy metabolite, currently monitored by anti-doping laboratories, was the most abundant and was detected for the longest time. Furthermore, four other long-term metabolites were identified. By ultra-performance liquid chromatography coupled to tandem mass spectrometry, only the drug and a known metabolite were detected after glucuronide hydrolysis, and phase II metabolites were not found. Thus, our results contribute to elucidating methasterone metabolism, including long-term metabolites besides of the 3α-hydroxy in routine doping analysis, which is very important due to variation in human metabolism.

Resumo em Inglês:

Density functional theory (DFT) (B3LYP/6-311++G(d,p)) calculations of the interacting strength 1,2-dithiolene anionic ligands with the [M(OH2)4]2+ and [M(OH2)2]2+ complexes (M = Ni and Zn) were performed. Three series of ligands were studied: compounds with an aromatic ring, with an ethylene moiety and with a heterocyclic ring. The ligands have substituents electron donors and acceptors by induction and resonance. Two substitution reactions were studied: the first is the substitution of two water molecules from the [M(OH2)6]2+ by a dithiolene anionic ligand (L2-) and the second is the substitution of two water molecules from the [M(OH2)4L] by another dithiolene anionic ligand. Geometric, electronic and energetic properties of the substituted aquacations are correlated with the metal-ligand affinity. All the substitution processes for both metal cations are spontaneous and are modulated by the electronic effect of each substituent of the ligand. Geometric parameters and chelation angle are correlated with the interaction strength. The energy decomposition analysis (EDA) results show that the electrostatic component is the main stabilizing term for the monosubstituted complexes, while for the disubstituted complexes the covalent term is the main stabilizing component. The polarization term is the main one to describe the covalent character. Natural bond orbital (NBO) shows the acid-base interaction nature of the metal-ligand bond.

Resumo em Inglês:

Ferulic acid (FERH) is known to exert leishmanicidal action against Leishmania (Leishmania) amazonensis. In this study, the ferulate anion (FER–) was intercalated into a layered double hydroxide (LDH) for FER– delivery during an antileishmania in vitro test. The LDH-FER– intercalation compound was prepared by coprecipitation and was characterized by X-ray powder diffraction, thermogravimetry, UV-Vis, infrared, and Raman spectroscopy analyses. Leishmania (L.) amazonensisin vitro assays were conducted to assess the LDH-FER– potential. LDH-FER– was found to promote a dose-dependent reduction of L. (L.) amazonensis amastigotes (intracellular form, half maximal inhibitory concentration (IC50) = 1.78 µg mL-1) without exerting a deleterious effect on the host macrophages (medium cytotoxic concentration (CC50) = 212.61 µg mL-1 and selectivity index = 119.4). LDH-FER– was found to be an effective inhibitor of the amastigote form of L. (L.) amazonensis, suggesting that LDH-FER– was able to deliver FER– inside the parasitophorous vacuoles where the pH is more acidic.

Resumo em Inglês:

An efficient sequential three-step reaction methodology for the synthesis of three new series-1-(prop-2-yn-1-yl)-1H-pyrroles, methyl 4-acetyl-1-((1H-1,2,3-triazol-4-yl)methyl)-1H-pyrrole-3-carboxylates and 6-((1H-1,2,3-triazol-4-yl)methyl)-2,6-dihydro-1H-pyrrolo[3,4-d]pyridazin-1-ones-is reported. The methodology comprises: (i) N-alkylation reactions of polyfunctionalized 1H-pyrroles-which were previously obtained from (E)-methyl 2-azido-3-arylacrylates-with propargyl bromide in order to obtain 1H-pyrroles; (ii) standard copper-catalyzed azide-alkyne cycloaddition (CuAAC) involving organic azides (benzyl-, 4-methoxybenzyl- and 4-chlorobenzyl, as well as n-octyl azide) and N-propargylated 1H-pyrroles to give triazolyl derivatives, as methyl 1H-pyrrole-3-carboxylates (click chemistry); and (iii) [4 + 2] cyclocondensation reactions of the ketoesters in the presence of hydrazine hydrochloride in order to furnish the desired series of pyrrolo[3,4-d]pyridazin-1-ones at total yields up to 54%.

Resumo em Inglês:

In this study, an in situ deep eutectic solvent-liquid-liquid microextraction method together with high performance liquid chromatography was developed for the determination of parabens in aqueous sample. The hydrophobic deep eutectic solvent, formed in situ by the DL-menthol and decanoic acid was used as the extraction solvent. Various parameters affecting the extraction efficiency including the composition of deep eutectic solvent, temperature of sample solution, extraction time, solution pH and salt concentration were investigated and optimized. Under the optimum conditions, the linear range of calibration curves was in the range of 3-1000 ng mL-1. The limits of detection and limits of quantification were in the range of 0.6-0.8 and 2.0-2.5 ng mL-1, respectively. The relative standard deviations were less than 7.2% for both intra-day and inter-days analysis. Finally, the proposed method was successfully applied to determine four parabens in environmental water samples with acceptable recoveries.

Resumo em Inglês:

In this study, a disposable pipette extraction (DPX)-based procedure was fully optimized for the multiclass determination of 12 pesticides, with significant differences in their physicochemical properties, using high-performance liquid chromatography coupled with diode array detection (HPLC-DAD). The variables optimized were type of extraction phase, sample pH, sample volume, number of extraction and desorption cycles, time of each cycle, type and volume of desorption solvent, and NaCl concentration of the samples. The analytical parameters of merit were determined under optimized conditions and satisfactory results were achieved, with limits of detection (LOQs) varying from 0.06 µg L-1 for carbofuran to 2.30 µg L-1 for carbendazim and correlation coefficients of 0.9923 to 0.9999. Relative recoveries ranged from 75 to 117%. Good results were achieved for intraday (n = 3) precision (1 to 20%) and interday (n = 9) precision (1 to 24%). The method was applied to the monitoring of 20 drinking water samples collected from water treatment plants.

Resumo em Inglês:

A novel electrochemiluminescence (ECL) biosensor for highly sensitive and selective detection of Ag+ is developed based on the sensitive “turn-on” structure-switching trigeminal structure of deoxyribonucleic acid (DNA-TS). DNA-TS consists of three oligonucleotides hybridized to form three double-stranded DNA like Y-shaped DNA structure. The formation of DNA-TS makes the ECL sign Ru(bpy)2(mcbpy-O-Su-ester)(PF6)2 of reporter probe approach to the electrode surface and thus increase the ECL signal intensity. The “signal-on” ECL biosensor could detect Ag+ concentration in the range from 1.0 × 10-11 to 3.2 × 10-9 mol L-1, and the limit of detection is 3.0 × 10-12 mol L-1. The strategy is sensitive and rapid. This approach could be extended to the design of sensors for other desired heavy metal ions as well. Such ECL sensors are promising for sensitive detection of other heavy metal ions.

Resumo em Inglês:

In the present work, a fast, easy and efficient analytical method was developed and validated for the determination of phenolic compounds (4-hydroxybenzoic, vanillic, caffeic, p-coumaric, sinapic, ferulic and ellagic acids, and naringenin) in red sweet pepper. Extraction of phenolic compounds was carried out using the quick, easy, cheap, effective, rugged and safe (QuEChERS) method, followed by separation and detection using ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). When the acetate version of the QuEChERS method was used, higher amounts of the phenolic compounds were extracted. In the dispersive solid phase extraction (d-SPE) clean-up step, combination of 50 mg of octadecylsilane (C18) and 7.5 mg of graphitized carbon black (GCB), resulted in the greatest removal of interferents, especially carotenoids, without significant retention of phenolic compounds. The recoveries for the proposed method were 82-103%, the limits of quantification were 2-150 µg kg-1, and the precision values expressed in terms of relative standard deviation (RSD) were ≤ 15%. The method developed was successfully applied to the analysis of different red sweet pepper cultivars.

Resumo em Inglês:

Predicting the compatibility of crude oils from different streams can be done by applying models that use the solubility parameter of the oils. The approximate solubility parameter value of a given crude oil can be calculated by observing the asphaltene precipitation onset caused by titration with n-heptane. For oils whose precipitation onset is not well defined, a small quantity of another petroleum with easily detected onset can be added. It would be ideal to always use the same petroleum for this addition, but this is obviously not possible. The purpose of this study was to replace this petroleum by a synthetic molecule. Therefore, molecules were selected and synthesized to obtain structures containing aromatic ring, aliphatic chain and heteroatom. The molecules were characterized by infrared spectrometry, gas chromatography-mass spectrometry, elemental analysis and gel permeation chromatography. Nitrated cardanol, polycardanol obtained by addition polymerization (PCA) and nitrated PCA presented the desired behavior. However, the concentration of the molecule in toluene needs to be adjusted in function of the characteristics of the petroleum. For a particular crude oil, when model molecule present solubility in a wider solubility parameter range, lower concentration will require to identify the precipitation onset of that oil.

Resumo em Inglês:

Reduction of silver cations followed by nanoparticle (Ag-NPs) synthesis is a model process to understand the reduction mechanism induced by a discharge over an aqueous surface, termed electrochemical plasma. This work aims at studying the silver reduction reaction steered by electrochemical plasma in the presence of other chemically active plasma-related interfaces, namely the plasma-gas and the liquid-gas interfaces. As no other plasma-induced species are able to reduce silver cations, the reduction of silver cations is employed as strategy to selectively detect the presence of hydrated electrons (e-h). The results demonstrate that the global rise of pH (increase in the content of OH-), observed for discharge in the helium gas phase, occurs in connection with the silver reduction, which is interpreted as a vivid experimental evidence of the second-order recombination reaction of theeh−2eaq−+2H2O→H2+2OH−. On the other hand, the global decrease of pH (increase in the content of H+) observed for discharge in mixed oxygen and nitrogen gas phase, is an event primarily driven by the Birkeland-Eyde process, and it is concomitant but spatially distinct from the electron injection. The acidification interferes in the NP formation, as NPs promptly dissolve in presence of HNO3. Only in complete suppression of the acidification, an experimental evidence of the reaction pathways for hydrated electron could be captured: e-h is competitively consumed through a scavenger-like reaction (reduction of silver cations in this work) and through the second-order recombination reactions of the e-h. The kinetic model proposed in this work further corroborates this interpretation.

Resumo em Inglês:

In this work, CdTe quantum dots (QDs) were controllably grown onto the surface of layered double hydroxide (LDH) aiming to develop a sensitive and selective method for the electrochemical detection of ciprofloxacin (CPX). Emission and absorption spectroscopy results as well as high-resolution transmission electron microscopy (HRTEM) images evidenced the formation of LDH/QD hybrid material. Unmodified carbon paste electrodes (CPE) as well as CPE chemically modified (MCPE) with native LDH and with the LDH/QD hybrid were prepared for CPX detection, revealing that MCPE-LDH/QD had the highest sensitivity for the detection of ciprofloxacin. Optimum detection conditions included a modifier dosage of 20% in MCPE, Britton-Robinson (BR) buffer (pH 6.0) as analytical medium, 300 s accumulation time and a scanning rate of 20 mV s-1. Linear current versus concentration curve was observed from 2.5 × 10-8-1.2 × 10-5 mol L-1 (coefficient of determination (R2) = 0.995), with sensitivity (limit of detection (LOD) = 4.2 × 10-8 mol L-1; limit of quantification (LOQ) = 1.3 × 10-7 mol L-1), precision (relative standard deviation (RSD) = 3.0%), accuracy (94.0%) and satisfactory selectivity in the presence of Zn2+, Fe2+, Cu2+, citric acid and ascorbic acid. Tests of CPX determination in commercial 500 mg ciprofloxacin tablets evidenced the applicability of the method.

Resumo em Inglês:

The resistance of Annona muricata roots to the nematode Meloidogyne javanica was investigated by nuclear magnetic resonance (NMR)-based metabolomics in combination with principal component analysis (PCA). Metabolic changes in roots exposed and not exposed to the nematode were evaluated and compared. In addition, the presence of nematicidal compounds in the root extracts was investigated through in vitro assay against Meloidogyne javanica second-stage juveniles. Plants exposed to nematodes showed significant changes in their metabolism after 24 h. Several resistance-related metabolites, including dopamine, xanthine and aromatic compounds, could be identified in the roots with the joint analysis of 1D/2D NMR and the loadings of PC3 (17.8%). A.muricata root chloroform extract, containing mainly acetogenins, has shown nematostatic activity against M. javanica, suggesting that a pre-formed defense mechanism can support the reported resistance. For the first time, metabolomic studies allowed to identify induced and pre-formed defense mechanisms and their related metabolites in Annona muricata.

Resumo em Inglês:

Polychlorinated dibenzo-p-dioxins and dibenzofurans are persistent organic pollutants which can mainly be found in the environment in water. These compounds are highly toxic and therefore developing new extraction methodologies that are simpler and cost less is highly desirable. This study aimed to optimize and validate the liquid-liquid extraction with low-temperature partition methodology of 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,7,8-tetrachlorodibenzofuran in water samples. The optimum extraction conditions were 8.0 mL of the acetonitrile and 4.0 mL of the water, homogenized in a vortex for 1 min and then maintained at -20 ºC for 1 h. The analytes recovery percentage was close to 100% and relative standard deviation was less than 7%. The methodology was precise, accurate, linear at 2.4-5.4 µg L-1, and selective, with a quantification limit of 2.4 µg L-1. The optimized methodology was applied in ten real samples and the results showed that these analytes were not detected.

Resumo em Inglês:

An alternative spectrophotometric ferric reducing activity power (FRAP) method for quantification of total reducing capacity (TRC) was developed. The method is based on the reduction of FeIII to FeII by antioxidant compounds containing 2,2’-bipyridine (bipy) in aqueous solution. Absorbance values recorded at 521 nm, characteristic of the Fe(bipy)32+ complex formed, were used to determine the TRC of some plants-derived beverages. For the teas samples, the TRC values obtained with the proposed method and cupric reducing antioxidant capacity (CUPRAC) reagent had an excellent agreement (adjusted correlation coefficient (r2) = 0.951). Concerning herbs samples, the TRC values obtained with the proposed FRAP method correlated very well with values obtained using the 2,2’-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS•+) method (adjusted r2 = 0.975). It can be inferred from these results that other beverages derived from plants (e.g., beers, wines, and fruits juices) could also be analyzed with this new FRAP assay. In addition, the reducing capacity of 21 phenolic derivatives was determined with the proposed method in order to elucidate their structure-reactivity relationship. As expected, the phenolic derivative structure changes greatly the TRC values obtained with this proposed FRAP assay.

Resumo em Inglês:

A new nanocomposite based on ZnCdTe semiconductor nanocrystals (NCs) synthesized in situ on reduced graphene oxide (rGO) was obtained. The heterostructure was characterized using UV-Vis emission and absorption spectroscopies, which provided evidences of the growth of the nanocrystals onto the rGO matrix. To evaluate the electrochemical performance, carbon paste electrodes modified with the nanocomposite (QD-rGO/CPE) were prepared, showing high sensitivity in the electroanalytical detection of the pesticide carbendazim. Under optimal operational conditions a calibration curve was constructed with a linear behavior in the range of 9.98 × 10-8 to 1.18 × 10-5 mol L-1, with a correlation coefficient of 0.997. The limit of detection (LOD) and the limit of quantification (LOQ) for carbendazim were 9.16 × 10-8 and 2.78 × 10-7 mol L-1, respectively. The electrode is successfully applied for the determination of carbendazim in orange juice samples.

Resumo em Inglês:

An automated method based on open-source hardware was created for the separation of porphyrins fractions from crude oil, an essential step for the quantification of V and Ni as metalloporphyrins. Preparative liquid chromatography was implemented with a reverse phase gradient from MeOH to toluene. The system allows three solvents and fractions changes by using quaternary valves connected to an Arduino microcontroller, programmed on the basis of the absorbance signal measured and its first derivative. Additionally, the method was applied to crude oils (Venezuelan National Institute of Standards and Technology (NIST) 8505 and from a marine reservoir). V and Ni were determined by inductively coupled plasma mass spectrometry (ICP-MS) and the V-porphyrin profile was determined by high performance liquid chromatography (HPLC)-ICP-MS. The concentrations of the metals grow in the last eluting toluene fractions, associated with asphaltenes. On the other hand, V-porphyrins in the first eluting MeOH fractions showed profiles of labile compounds, with a higher percentage in the Brazilian crude oil (4.9 mg L-1, corresponding to 18% of total V), in comparison to the one from the biodegraded NIST 8505 (59 mg L-1, corresponding to 7% of total V). The overall methodology has a good reproducibility and provides information on elements concentrations associated with porphyrin class compounds.

Resumo em Inglês:

The synthesis of efficient and reusable gold-based catalysts for the selective oxidation of alcohols is a strategy for the development of green processes. Pre-formed nanoparticles syntheses are an easy way to produce controlled-nanosized gold materials; however, the selection of a support is not trivial. Herein, we proposed a CoFe2O4 support enriched with Sr(OH)2, which holds remarkable properties and is suitable for the synthesis of a stable gold-based catalyst for the oxidation of benzyl alcohol. We suggested that the interaction between the CoFe2O4 and the Sr(OH)2 is highly important for the performance of the catalyst. Under the base-free condition of 2.5 h, 100 ºC and 2 bar of O2, the catalyst reached 58% of conversion with 76% of selectivity to benzaldehyde. With K2CO3 addition, the conversion and selectivity to benzaldehyde increased to 87% and 88%, respectively. Any gold leaching was detected in 5 successive runs, attesting the noticeable stability that the catalyst presents. This work provides great potential for the selective oxidation of alcohols with high activity since the magnetic properties of the catalyst provide an easy route and allows the separation of the medium reaction. In addition, we are here proposing an important interaction between the Sr(OH)2 and the magnetic nanoparticles.

Resumo em Inglês:

Short-chain fatty acids (SCFA) are compounds produced during fermentation of gut microbiota. Acetic, propionic and butyric acids are the most important SCFA produced from non-digestible foods. We developed and validated a rapid and low-cost capillary electrophoretic (CE) method for determination of acetic, propionic and butyric acids in mice feces (100 mg of sample). Electrophoretic separation was performed for SCFA determination in feces samples during 10 min. The method showed good linearity for all analytes (determination coefficient, r2 > 0.98); recovery from 74.1 to 109.8%, while the intra- and interday precision essays were suitable (relative standard deviation (RSD) < 10%); and limits of detection and quantification of 0.13-0.43 mM for acetic acid, 0.09-0.29 mM for propionic acid and 0.03-0.09 mM for butyric acid. Real samples of mice dextran sulfate sodium-induced colitis feces treated with jabuticaba (Plinia cauliflora) aqueous extract were performed successfully.

Resumo em Inglês:

We describe the microwave-assisted synthesis of thirteen functionalized peptoids and evaluate their in vitro antileishmanial activity against forms of Leishmania (Leishmania) amazonensis promastigotes. Synthesis via the Ugi four-component reaction (Ugi 4CR) reaction furnished the compounds of interest in 55-80% yield; reactions were conducted in a microwave reactor and lasted only 10 min. We then screened the antileishmanial activity of the synthesized compounds in vitro. To determine the IC50 (inhibitory concentration necessary to inhibit the growth of 50% of parasites) values, we selected the compounds that inhibited L. (L.) amazonensis growth by more than 50%. The seven selected compounds displayed IC50 values ranging from 2.6 to 72 µM after incubation for 48 h. Three peptoids gave IC50 values between 2.6 and 7.9 µM and can be considered as bioreactive molecules (hit criteria).