Determination of resveratrol and piceid in beer matrices by solid-phase extraction and liquid chromatography-tandem mass spectrometry

Beer is one of the most commonly consumed undistilled alcoholic beverages in many countries. In recent studies, the stilbenes resveratrol and piceid have been found in some hop varieties which are used in the production of beer. Therefore, they could be transferred to beer. The aim of the present work was to validate a method to study the potential content of trans- and cis-resveratrol and piceid in 110 commercial beers from around the world. The resveratrol and piceid contents of 110 beers were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) after a solid-phase extraction (SPE) using optimized and validated procedures for the beer matrix. The beer matrix effect was also studied. Stilbenes were found in quantifiable amounts in 92 beers, while concentrations below the limit of quantification (LOQ) were found in 18 beers. Resveratrol was found in the range of 1.34-77.0μg/L in 79% of the beers analyzed, and piceid was found in the range of 1.80-27.3μg/L in only 33% of them. The mean of total resveratrol in all the beers was 14.7±20.5μg/L. The content of resveratrol has been compared with other resveratrol containing foods. A serving of beer contains similar amounts of stilbenes as berries, less than chocolate and grape products but more than pistachios, peanuts or tomatoes. Overall, beer is one of the products with the lowest levels of total resveratrol (μg/L), and despite its high consumption it should not be considered as a representative source of resveratrol.     

High-pressure high-temperature synthesis and crystal structure of the isotypic rare earth (RE)-thioborate-sulfides RE9[BS3]2[BS4]3S3, (RE=Dy-Lu)

Application of high-pressure high-temperature conditions (3.5 GPa at 1673 K for 5 h) to mixtures of the elements (RE:B:S=1:3:6) yielded crystalline samples of the isotypic rare earth-thioborate-sulfides RE₉[BS₃]₂[BS₄]₃S₃, (RE=Dy-Lu), which crystallize in space group P6₃ (Z=2/3) and adopt the Ce₆Al_3.33S₁₄ structure type. The crystal structures were refined from X-ray powder diffraction data by applying the Rietveld method. Dy: a=9.4044(2) Å, c=5.8855(3) Å; Ho: a=9.3703(1) Å, c=5.8826(1) Å; Er: a=9.3279(12) Å, c=5.8793(8) Å; Tm: a=9.2869(3) Å, c=5.8781(3) Å; Yb: a=9.2514(5) Å, c=5.8805(6) Å; Lu: a=9.2162(3) Å, c=5.8911(3) Å. The crystal structure is characterized by the presence of two isolated complex ions [BS₃]^3- and [BS₄]^5- as well as [□(S^2-)₃] units.     

An straightforward entry to new pyrazolo-fused dibenzo[1,4]diazepines

A series of novel pyrazolodibenzo[1,4]diazepines has been synthesized with good overall yields. The diarylpyrazole intermediates, with structure similarity to biologically relevant compounds such as currently marketed drugs like rimonabant or celecoxib, were prepared by a tandem sequence amine-exchange/heterocyclization starting from readily available enaminones and arylhydrazines. The key step of this efficient methodology was C(aryl)-N bond construction, accomplished by a palladium-catalyzed intramolecular N-arylation reaction, which was conducted in both homogeneous and polymer-supported versions. Reaction scope of such protocols and recycling of the heterogeneous catalyst were also examined.     

Structure analysis and photocatalytic properties of spinel zinc gallium oxonitrides

This report describes a detailed structural, electronic, and catalytic characterization of zinc gallium oxonitride photocatalysts with a spinel crystal structure. The bandgap decreases to less than 3 eV with increasing nitrogen content (<3 wt%) and these photocatalysts are active in visible light (λ>420 nm) for the degradation of cresol and rhodamine B. Density functional theory calculations show that this bandgap reduction is in part associated with hybridization between the dopant N 2p states and Zn 3d orbitals at the top of the valence band. X-ray photoelectron measurements indicate that nitrogen is indeed interacting with the oxide precursor through the formation of both nitride- and oxonitride-type species. The incorporation of nitrogen reduces the uniformity of the local structure of the spinel Zn-Ga-O-N (ZGON) species, as reflected in X-ray absorption spectra and Raman measurements relative to zinc gallate, which suggests the presence of defects. The oxonitrides exhibit faster photocatalytic rates of reaction than the oxide precursor. The degradation mechanisms were determined to be via the attack by hydroxyl radicals and holes for rhodamine B and cresol, respectively. Addition of Pt as a co-catalyst increased the rate of photodegradation, a result attributed to better charge separation.     

Survey Of Long d(10)-d(10) Metallophilic Contacts in Four-Membered Rings of Ag(I) and Au(I) Supported by Carbene-Pyrazole Mixed Ligands

The interesting case of long intramolecular d(10)-d(10) contacts has been studied through [Ag(4)L(2)](2+) and [Au(4)L(2)](2+) (L = 3,5-bis((N-methylimidazolyl)methyl)pyrazole) systems, showing interesting features gained by analysis of the electronic structure and the overall shielding tensor in the molecular domain, in terms of its components. The long intramolecular closed-shell separations are attributed to the population of the bonding, nonbonding, and antibonding combinations of the ns atomic shells in the [M(4)](4+) core, contrasting with that observed in systems with shorter d(10)-d(10) distances. This point allows to concludeb that separations shorter then the sum of the van der Waals radii (3.4 ? for Ag-Ag, and 3.2 ? for Au-Au) of the nucleus involved requires a net bonding population between ns and np atomic shells of the d(10) closed-shell centers. Moreover, [Au(4)L(2)](2+) exhibits an increased covalency observed for the enhanced charge-donation due to the stabilization of the ns and destabilization of the (n - 1)d driven by the relativistic effects. The magnetic response denotes a slight interaction between the closed-shell centers at distances in the range of their sum of van der Waals radii because the observed remote effect (or anisotropic effect) caused by each d(10) nucleus does not influence considerably the neighbor center. The analysis of δ in terms of its components allows to conclude that the [Au(4)L(2)](2+) system exhibits an increased magnetic response due to the increase in the number of the inner-electrons in comparison to [Ag(4)L(2)](2+).     

Surface Modification of Banana Fibers by DBD Plasma Treatment

Banana fibers, an environmentally friendly raw material freely available, were physically modified by atmospheric dielectric barrier discharge (DBD) plasma treatment of different dosages. The influence of the plasma treatment applied on the banana fibers was performed considering the mechanical properties, wettability, chemical composition and surface morphology. These properties were evaluated by tensile tests, static and dynamic contact angle, Fourier transform infrared spectroscopy, energy dispersive spectroscopy, X-ray diffractometry, conductivity and pH of aqueous extract, differential scanning calorimetry and scanning electron microscopy images. We compare untreated and treated fibers with three different DBD plasma dosages. The results of this study showed considerable modifications in banana fibers when these are submitted to plasma treatment.