Resumo em Inglês:

This work describes the preparation of the C(7)-C(20) fragment of spirotoamides A to C in a very elegant fashion, achievement very high levels of stereocontrol. The synthesis has been accomplished by a sequence involving 14 steps (0.36% overall yield, average of 81% for each step) in high diastereo and enantioselectivity, employing, as determining steps, asymmetric Mukaiyama and boron-mediated 1,5-anti promoted aldol reactions between α-methyl-β-hydroxyketones and aldehydes.

Resumo em Inglês:

Human milk (HM) lipids provide about 50% energy and facilitate the transport and absorption of fat-soluble vitamins for infants, but their composition should be studied when the milk is processed. This study evaluated the lipid quality of lyophilized and vacuum-packed colostrum (C), transitional (T), and mature (M) HM for a period of 1, 30, 60, 90, 120, 150, and 180 days of storage at –18 ºC. From the acidity (ºDornic), lipid content, and fatty acid (FA) composition results, no significant differences in the analyzed period were observed. The relative percentage of major triacylglycerols (TAG) of the HM was not altered, showing that the lyophilization process in HM is a good alternative that could be applied in human milk banks (HMB), increasing HM preservation and facilitating its transport and storage.

Resumo em Inglês:

This paper reports the droplet size distribution (DSD) measurements in 28 W/O (water/oil) crude oil emulsions prepared with two Brazilian oils (medium and heavy) under different shear conditions using both 10 g L-1 NaCl solution and water production by low field nuclear magnetic resonance (NMR, 2.2 MHz). The PFGSTE (pulsed-field gradient-stimulated echo) pulse sequence applied was able to separate the crude oil emulsion signal for both medium and heavy oil even for low dispersed phase content (1.51 wt.%) and took into account only the aqueous phase signal. All emulsions exhibited an average diameter smaller than 5.5 µm because of the severe shear conditions. Despite the difficult processing of the S24 (6.48 wt.%) emulsion signal, good agreement was achieved between low field NMR and low-angle laser light scattering (LALLS) results. Finally, the paramagnetic ions in the water production did not affect the NMR measurements, demonstrating its applicability for analyzing real emulsions.

Resumo em Inglês:

Sol-gel synthesis is commonly used to modify the surface of mesoporous silica nanoparticles (MSN) with organic groups through the co-condensation method. The template removal, and the site-controlled addition of organic groups and their partial occlusion inside the framework walls are still a challenge in the one-pot synthesis. Here, we optimize the synthesis of amino-modified MSN by the combination of efficient template removal methodology with the precise time of the amino precursor addition to achieve superb mesoporous material. The addition after the growth process produces a sample with a significantly higher amount of NH2 on the external surface when compared to the standard procedure. The template removal by reflux with isopropanol/H+ eliminated ca. 90% of cetyltrimethylammonium bromide (CTAB), and preserved the mechanical and thermal properties, even with thin walls (2.1 nm). The synthesized nanoparticles possess stability, appropriate size, and a positive surface. This makes them excellent nanocarriers, especially in the biomedical field.

Resumo em Inglês:

Agro-industrial wastes are abundant and low-cost sources of energy and chemicals. Biomass account for 14% of the world’s energy production. Industrial residues of production of soluble coffee (spent coffee grounds - SCG) have great potential due to its large-scale production and can be transformed by pyrolysis, in liquid, solid and gaseous products with applications from energy to chemicals. This work has the objective of producing bio-oil from the pyrolysis of industrial SCG, characterize it by chromatography and indicate its possible applications. As SGC contains a large amount of glycerides, they were extracted from SGC before the pyrolysis, aiming to obtain a better bio-oil from the residue. The yield in vegetable oil was 5.2% and its analyses showed that 50% are saturated acids (mainly palmitic 27.6%) and other 50% are unsaturated ones (mainly linoleic acid 35.3%). This composition qualifies this oil for biodiesel purposes. The residue (SGC after extraction) was submitted to pyrolysis, yielding 30% in liquid products, being 6% bio-oil. The bio-oil was analyzed by gas chromatography being identified free fatty acids, hydrocarbons, phenols and N-compounds. The heteroatomic compounds limit the use as biofuel but can be interesting for the pharmaceutical, agrochemical and fine chemicals industries.

Resumo em Inglês:

Myracrodruon urundeuva (Anacardiaceae) is the scientific designation of “aroeira-do-sertão”, a tree well dispersed at the northeastern Brazil. The medicinal use of this plant is widespread throughout the rural population and the inner trunk bark decoction is used to treat cutaneous affections, urinary and respiratory diseases, and gynecological problems. “Aroeira-do-sertão” has been included in the list of native species under extinction threat. In order to find a sustainable source of the plant, seedlings have been cultivated. The purpose of this work was to investigate the chemical composition of the decoction from leaves of cultivated plants (aqueous extract from Myracrodruon urundeuva (AEMU)) and its anti-inflammatory activity on human neutrophils. The addition of AEMU on cells suspension inhibited significantly its activation/degranulation induced by phorbol myristate acetate. AEMU since at 50 µg mL-1 showed better pattern of inhibitions when related to indomethacin, non-selective cyclooxygenase inhibitor used as reference anti-inflammatory. The decoction fractionation was performed by high-speed counter-current chromatography (HSCCC) and semi-preparative high-performance liquid chromatography (HPLC) using a phenyl column as the stationary phase, allowing the isolation of 24 compounds. These results showed how the AEMU is rich in bioactive metabolites, which probably contribute for the anti-inflammatory effects of this plant extract, modulating the degranulation of human neutrophils, one of the pro-inflammatory mechanism of these cells.

Resumo em Inglês:

A combined phytochemical, crystallographic and biological study of Worsleya procera roots was performed. Fifteen alkaloids were identified by gas chromatography mass spectrometry (GC-MS) and seven of them were isolated. The structures of the alkaloids were elucidated by spectroscopic methods, and a detailed crystallographic study of tazettine was carried out. The isolated alkaloids and the obtained extracts were tested in vitro against Plasmodium falciparum (3D7 and K1 strains) and human hepatocarcinoma cells (HepG2) to assess their antiplasmodial and cytotoxic effects, respectively. One of the isolated alkaloid derivatives, lycorine, exhibited antiplasmodial activity against both sensitive (3D7) and resistant (K1) parasite strains in the low micromolar range (half-maximal sample inhibitory concentration (IC50) values of 2.5 and 3.1 µM, respectively) and displayed a low cytotoxicity profile, with a selectivity index greater than 100. Our findings indicate that lycorine is a hit for antimalarial drug discovery.

Resumo em Inglês:

This work describes the preparation of Pt/C, PtxSny/C and PtxSny(CeO2 nanorods/C) nanoparticle catalysts synthesized by the chemical reduction method via sodium borohydride for the ethanol oxidation reaction. Using X-ray diffractogram analysis, it was verified that no alloy formation occurred between platinum (Pt) and tin (Sn). The distribution of the nanoparticles in the support occurs in a more agglomerated form for the materials containing Sn and CeO2 nanorods (NR). The electrocatalyst Pt3Sn1_20%NRCeO2/C was highlighted in CO-stripping experiments because it showed the lowest onset potential for CO oxidation and the highest value for the electrochemically active surface area. The other electrochemical experiments for ethanol oxidation showed similar activities for the Pt3Sn1/C and Pt3Sn1_20%NRCeO2/C electrocatalysts. The observed effect can be associated with defects in the structure of the CeO2 nanorods, the electrochemical active surface area, and the properties of the CeO2 nanorods related to enhancing the generation of oxy-hydroxy species at lower potentials compared to PtSn/C electrocatalysts, which increased the CO oxidation as measured using stripping experiments. For this reason, it is possible to both use less platinum and to obtain behavior close to that of PtSn/C electrocatalysts for ethanol oxidation reaction (EOR).

Resumo em Inglês:

In this study, a novel type of tris(2-acyl-1,3-indandione)-aluminum(III) coordination compounds of the general formula [Al(acind)3]H2O, where 2-acyl-1,3-indandione (acind), 2-acetyl-1,3-indandione (aind), 2-benzoyl-1,3-indandione (bind), and 4-methyl-2-benzoyl-1,3-indandione (mbind), were synthesized and characterized by elemental analysis (CHN), Fourier transform infrared (FTIR) and nuclear magnetic resonance (1H NMR) spectroscopies, thermal analysis (TG/DTG and DTA), and optical absorption spectroscopy in the UV-Vis region. These compounds present remarkably high green luminescence in powder and in thin-film forms. However, when these compounds are applied in glass/ITO/β-NPB/spiro-2CBP/[Al(acind)3]/Al and glass/ITO/β-NPB/[Al(acind)3]/LiF/Al electroluminescent devices, where spiro-2CBP is 2,7-bis(carbazol-9-yl)-9,9-spirobifluorene and β-NPB is N,N’-bis(naphthalen-2-yl)-N,N’-bis(phenyl)-benzidine, the emission color tuned from green to red, reflecting a change from the direct charge recombination in the emitting layer of the [Al(acind)3] complexes to an exciplex-based emission in which [Al(acind)3] complexes and spiro 2-CBP acted as acceptor and donor, respectively. These results suggest that [Al(acind)3] complexes have potential applications as molecular light converter materials for fabricating new electroluminescent devices.

Resumo em Inglês:

The rises of toxic effects caused by pesticides are of concern. However, Brazilian legislation still needs scientific subsides to improve the water quality requirements. This can be attributed in part to the few existing studies showing the occurrence and levels of multi-residue pesticides. Therefore, the objective of this study was to investigate the presence and the residue-levels of pesticides in surface, ground and drinking water of Tibagi River micro-basin in Paraná State, Brazil. Data obtained over a year for the physical-chemical parameters, screening and quantification, made by liquid chromatography-tandem mass spectrometry (LC-MS/MS), confirmed the contamination by several pesticides. Alarming concentrations of diuron and imazethapyr in a permanent preservation area and in groundwater were observed. The absence of legislation for most pesticides under study makes difficult the prohibition of their use and the control of their residue-levels on the environment. The results draw attention to further discussion and engagement around the pesticide regulations.

Resumo em Inglês:

Herein, the synthesis, characterization and catalytic application of an organic-inorganic, palladium (Pd)-containing hybrid material, poly(amidoamine)-cyclodextrin (Pd@PAAs-CD), is reported as an efficient catalyst for Suzuki-Miyaura coupling reactions. The structure of Pd@PAAs-CD was confirmed by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), inductively-coupled plasma atomic emission spectroscopy (ICP-AES), and 1H nuclear magnetic resonance (NMR) spectroscopy. Furthermore, an efficient protocol has been developed using Pd@PAAs-CD as the catalyst in a Suzuki-Miyaura cross-coupling reaction in an aqueous medium in high yields. By using cyclodextrin (CD) as the mediator grafted onto PAAs, the Pd nanoparticles (NPs) were dispersed and enhanced the catalytic reaction by promoting host-guest interactions with the CD. In addition, the reusability of the Pd@PAAs-CD hybrid material is demonstrated for use in multiple sequential cross-coupling reactions.

Resumo em Inglês:

The effect of noble metal catalysts supported on an ionic exchange resin for the enantioselective hydrogenation of ethyl pyruvate to ethyl lactate was studied. High activity and moderate enantioselectivity levels were obtained. Pt was the best enantioselective metallic phase, followed by Pd and Au; Rh was the less enantioselective metallic phase. The effect of the active site was evaluated for the most enantioselective catalyst: 2Pt-WA30 (prefix indicates the metal loading). A novel method for sintering the Pt metal particles by nitriles reduction was used, and a controlled migration of the metal particles to the surface layers was observed. There existed an optimal particle size with maximization of the enantiomeric excess, corresponding to 24 h sintering. The hydrogenation of ethyl pyruvate to ethyl lactate was found to be structure-sensitive and the importance of the metal particle size for the adsorption of the chiral modifier was proved. Two different chirality induction methods were tried for the 2Pt-WA30 catalyst: (i) the addition of the chiral modifier (CM) to the reaction media, or (ii) the modification of the catalyst in a swelling medium prior to the reaction in order to encapsulate CM. Lower activity but higher enantioselectivity levels were obtained with method (ii). Finally, the reuse of the catalysts was also assessed by means of consecutive reaction tests.

Resumo em Inglês:

For Q235 carbon steels in 0.01 mol L-1 NaNO2-HCl solutions with different pH values, the effects of pH values on the functional mechanisms of nitrite anions (NO2-) were studied. In the pH 1 and pH 2 solutions, the Q235 steels showed the electrochemical behavior of activation, and uniform corrosion (UC) was the main corrosion type on the Q235 surface. The presence of NO2- did not affect the electrochemical behavior and the corrosion type but only accelerated the anodic reaction of Fe oxidation. In the pH 3 and pH 4 solutions, the Q235 steels presented the electrochemical behavior of activation-passivation transition, and intergranular corrosion (IGC) occurred on the Q235 surface. The cathodic reaction of NO2- reduction resulted in the transition of electrochemical behavior from activation to passivation and the change of corrosion type from UC to IGC. In the pH 5 and pH 6 solutions, the Q235 steels exhibited the electrochemical behavior of self passivation-pitting, and pitting corrosion (PC) was present on the Q235 surface. The strong oxidability of NO2- played a critical role in the formation of γ-Fe2O3 passive film on the Q235 surface under the combined action of Fe2+ and NO2-.

Resumo em Inglês:

Zika virus (ZIKV) is a mosquito-borne pathogen which is a current global public health concern. There are currently no approved vaccines or antivirals against ZIKV infection. Taking into account that naphthoquinones have shown promising antiviral activity, the aim of this study was to describe the screening of two bis-naphthoquinones series against ZIKV. Twenty seven compounds were evaluated against ZIKV using Vero cells. The findings showed that among the compounds analyzed four were promising. Compound 3,3’-((2-nitrophenyl)methylene)bis(2-hydroxynaphthalene-1,4-dione) containing the nitro group at the ortho position showed the best selectivity index, followed by compound 3,3’-(4-chlorophenylmethylene)bis(naphthalene-1,2,4-triyl triacetate) with the chlorophenylmethylene radical. These results demonstrate that these bis-naphthoquinones are largely effective in inhibiting the replication of ZIKV.

Resumo em Inglês:

A series of tetrakis-β-diketonate Q+[Ln(β-dik)4]–, where Ln = GdIII or EuIII, Q = ammonium cations and β-dik = tta (2-thenoyltrifluoracetone) or bmdm (1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)-1,3-propanedione) have been synthesized and characterized. The environment surrounding the EuIII ion depends on the lateral groups of the ligand and on the alkyl chains of the counter ion Q. The shortest lifetime (τ) = 0.29 ms, and lowest quantum efficiencies (η) = 24%, were obtained for (N(C12H25)2(CH3)2)+[Eu(bmdm)4]–, while (N(C4H9)4)+[Eu(bmdm)4]– has the longest τ = 1.04 ms and η = 90%. The Judd-Ofelt intensity parameters (Ω2 and Ω4) strongly changes for tta series pointing to stronger ion-dipole interactions between the –CF3 group with the ammonium cations. The agreement between the experimental results of photoluminescence and theoretical data suggests that the geometries optimized by the Sparkle model are correct. These results point to potential candidates for building up Langmuir-Blodgett (LB) luminescent films, since it is possible to maximize the intermolecular interactions and the photoluminescent properties of tetrakis LnIII complexes.

Resumo em Inglês:

Density functional theory calculations (ωB97X-D/6-311++G(d,p)) are employed to investigate an alternative pathway for Prins-like cyclization. Although strong acids usually catalyze this reaction, 4-amino-1,3-dioxanes are rapidly obtained in high yields without catalyst when benzenamines and acetaldehyde react at low temperatures, in aqueous medium. Considering these conditions, we applied a supermolecule model with explicit water molecules to compute the mechanism for 4-amino-1,3-dioxanes formation from the reactants. The structure of the primary solvation shell was determined by Metropolis Monte Carlo method. In the Prins-cyclization step, we found an unpredicted pathway with non-ionic transition structures or intermediates. Explicit water molecules establish a net of hydrogen bonds allowing prototropism, maintaining the electrical neutrality in the system while two protons transfer occurs. To provide data to further experimental confirmation of this hypothesis, we estimated the kinetic isotope effect for the reaction. We also investigated the use of aliphatic amines, which indicates that the reaction may be of a broader application than first observed experimentally.

Resumo em Inglês:

Sesquiterpene lactones are an important class of secondary metabolites frequently isolated from Vernonanthura genus that present a variety of biological properties, including antiproliferative activity. Due to the limitation of pharmacological studies on Vernonanthura nudiflora, the aim of this work was to investigate their antioxidant potential and antiproliferative activity against human tumor cells, as well as to isolate and identify the chemical constituents present in their aerial parts. The phytochemical investigation resulted in the isolation of the sesquiterpene lactones piptocarphins A, B, D, and a new hirsutinolide derivative, 8α-tigloyloxy-10α-hydroxy-hirsutinolide, besides triterpenes, glycosylated steroids, flavonoids, and one chlorogenic acid derivative. Also, other sesquiterpene lactones were identified by ultra-high performance liquid chromatography-high resolution tandem mass spectrometry (UHPLC-HRMS/MS) from dichloromethane fraction. This fraction showed activity against the tumor cells tested, mainly against leukemia, glioma, ovarian and kidney, with growth inhibitory activity (GI50) less than 0.80 µg mL-1. Piptocarphins A and B, in mixture, showed strong activity against all human cancer cell lines tested, with GI50 values ≤ 0.15 µg mL-1. Piptocarphin D was selective for glioma and resistant ovarian cell lines. The new hirsutinolide derivative showed potent activity against breast (GI50= 0.96 µg mL-1) and resistant ovarian (GI50 = 3.60 µg mL-1) cell lines.

Resumo em Inglês:

Poly(ε-caprolactone), an aliphatic polyester with biodegradability and cytocompatibility, has been used to create scaffolds for tissue engineering purposes. However, the hydrophobicity and low water absorptivity of poly(ε-caprolactone) reduce cell anchorage on their membranes. Here, poly(ε-caprolactone)-based scaffolds were prepared by electrospinning of poly(ε-caprolactone)-chitosan blend, and poly(ε-caprolactone)-dexamethasone solution. Chitosan and dexamethasone play an essential role to increase the scaffolding performance of poly(ε-caprolactone)-based electrospun membranes. A poly(ε-caprolactone) membrane without chitosan and dexamethasone did not provide satisfactory results to promote cell culture of adipose mesenchymal stem cells (AMSCs). Compared to the poly(ε-caprolactone)-dexamethasone surface, poly(ε-caprolactone)-chitosan membrane imparts better cytoskeletal reorganization, and cell spreading, increasing the strength of cell attachment. Also, poly(ε-caprolactone)-chitosan composite provides strong antimicrobial activity against Pseudomonas aeruginosa (ca. 90% inhibition). Therefore, the poly(ε-caprolactone)-chitosan composite is a better alternative to treat skin diseases and promote skin regeneration than conventional approaches based on dexamethasone.

Resumo em Inglês:

Oxidative stability parameters (OSP), acid value (AV), water content (W), and the metallic copper corrosion rate in biodiesels obtained from eight different vegetable oils were determined. Simple and multiple linear regression models were constructed to explain the influence of the OSP, AV and W variables on the corrosion rate. The corrosion rate was lower in biodiesel with less oxidative stability because, instead of reacting with copper, O2 reacted preferentially with the unsaturated fatty acid methyl esters (FAME) that could act as “sacrificial molecules” to protect the copper against corrosion. Therefore, the corrosion rate was strongly related to the FAME composition. The AV was an important parameter in the corrosion process because free acids react with passivating agents, increasing the corrosion rate. The predictive capacity of W for corrosion rate was statistically insignificant, although water condensed on a copper surface causes corrosion.

Resumo em Inglês:

A simple and sensitive electrochemical impedance spectroscopy (EIS) biosensor was designed for the determination of lipopolysaccharide (LPS). The gold nanoparticles (GNPs) were electrochemically deposited on the glassy carbon electrode as a base electrode and the biosensor was fabricated by self-assembling a special peptide (GIGKLHSAGKF) used as molecular recognition onto the GNPs surface according to the Au–S bond. Polyethylene glycol and 6-mercapto-1-hexanol were used to block the remaining sites of the modified electrode surface. When binding of LPS, the biosensor had a good response to different concentrations of LPS and the charge transfer resistance of the biosensor was directly related to the logarithm of LPS concentrations in the range of 0.01 pg mL-1-1.0 ng mL-1 with a limit of detection of 2.0 fg mL-1. The characteristics of the electrochemically deposited GNPs and the optimization concentration and the self-assembly time of peptide, as well as the performance of the EIS biosensors for LPS were investigated. The biosensor was used for real serum sample determination with satisfactory results.

Resumo em Inglês:

Two types of manganese oxide were investigated for the removal/degradation of Orange G (OG) dye in aqueous solution. One manganese oxide (pyrolusite) was obtained commercially and the other (birnessite) was prepared according to the polyol method by means of the oxidation of MnII hydroxide by H2O2. Both materials were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), and nitrogen adsorption/desorption at 77 K. The effects of agitation time, pH, and MnO2 dose on the degradation of OG by the birnessite and pyrolusite were evaluated. Approximately 90 and 99% decoloration of OG (10 mg L-1) was obtained after 30 min of stirring with 0.20 g L-1 of birnessite or pyrolusite, respectively. The decoloration and increased intensity of absorbance bands in the UV-visible spectrum were indicative of a degradation process that followed pseudo-first order kinetics. The findings demonstrated the high efficiency of different types of manganese oxides for removal of this organic pollutant from waters.

Resumo em Inglês:

An environmentally benign method is described for the α-hydroxylation of malonates and cyclic analogues in aqueous medium at room temperature under mild conditions, based on the in situ generation of dimethyldioxirane through the combination of acetone and Oxone®. This procedure was found to be substrate-dependent and was successfully performed to provide α-hydroxylated γ-lactones. To demonstrate the synthetic potential of this mild α-hydroxylation, two different concise routes were developed to synthesize harzialactone A in the racemic form with a moderate (3:1) diastereomeric ratio.