Antioxidant activity of aryltetralone lignans and derivatives from Virola sebifera (Aubl.)

Aryltetralone lignans bearing methylenedioxy groups (1a-b; 2a-b) were isolated from seeds of Virola sebifera. Their antioxidant activities were evaluated by inhibition of lipid peroxidation as indicated by TBARS and chemiluminescence emission (CL) assays. The lignan 1c, 'having a 2'-hydroxy-4',5'-methylenedioxyphenyl group, was the most active compound with TBARS/CL Q 1/2 values of 0.89 and 0.10 microg/mL, respectively. The catechol derivatives 3 and 4, obtained by demethylenation of lignans 1a and 2a, were of similar activity to 1c, and all were much more effective as antioxidants than alpha-tocopherol.     

Determination of aniline by adsorptive stripping voltammetry using an improved diazotization and coupling procedure application to the evaluation of the light degradation of D&C red no. 33 in the presence of ascorbic acid

A method for the determination of aniline was developed, based on the diazotization and coupling of the aromatic amine to form an azo compound capable of being determined by adsorptive stripping voltammetry. A fast derivatization procedure was developed using 1-naftol as the coupling agent. A detection limit of 0.8 mug/l was obtained for aniline, using an accumulation time of 2 min. The method was applied in the determination of the amount of aniline in the colouring matter D&C Red No. 33, after a liquid-liquid extraction with chloroform, before and after submitting the colouring matter to a process of degradation, using accelerated light conditions in the presence of ascorbic acid.     

New designs for inhibitors of the NF-κB: DNA binding

We present a series of new inhibitors of the association between nuclear factor kappa B (NF-B) and the corresponding B site in DNA. They were designed using the lead compound 15-deoxy-^12,14 -prostaglandin J₂ (PGJ2), which is a natural product with demonstrated inhibitory efficiency for this system. First, the binding mode of PGJ2 to NF-B was unraveled by GOLD docking calculation. Subsequently, substitutions were made to PGJ2 to optimize its association with NF-B. Care was taken not to strongly increase the reactivity of the new compounds, and to keep the overall shape, size and hydrophilicity of the lead compound, which should render them a similar bioavailability. Molecular mechanics calculations were performed to decide on the suitability of the substitutions, and to evaluate the energies of association with NF-B. Density functional theory calculations were performed also to study the overall reactivity of the substituted drugs towards NF-B. Important general conclusions were obtained, concerning the improvement of these natural inhibitors; namely, a set of rational methodologies were deduced to improve the association between the PGJ2 derivatives and NF-B, and their efficiency demonstrated by generating a set of substituted complexes, some of them with a very much increased affinity for NF-B, opening new doors to enlarge the therapeutic capabilities of this class of drugs.     

Study of cork (from Quercus suber L.)-wine model interactions based on voltammetric multivariate analysis

The cork from Quercus suber L. is the premium raw material used to produce wine-bottling stoppers; however, being a natural product, cork can be contaminated and attacked in different ways that could promote differences in its proprieties. A specific contamination is the defect known in the industry as “Mancha Amarela—Yellow spot” (MA). This cork shows modifications in its mechanical, structural and optical properties and is potentially able to cause off-flavours in wine. In this study, a new analytical approach is proposed for the rapid screening of cork-wine model interactions in order to determine if the cork were able to contaminate a wine. Cork samples classified as standard (S) and cork MA were put in contact with a wine model matrix. The model matrix was analysed by cyclic voltammetry and square wave voltammetry in function of different contact times. Considering that matrices in contact with cork S and MA exhibited different pH, the influence of this parameter on the distinction power was also evaluated. The data sets obtained from the different techniques were treated by principal component analysis (PCA) and PLS_Cluster. The major difference between samples S and MA is the occurrence of an important peak at ca. 580 mV in the MA voltammograms. This more positive peak may be assigned to lignin related phenolics; therefore, it can be proposed as a possible marker to follow lignin degradation.     

Distant-dipole field in liquids and diffusion: a perturbative approach

A perturbative approach is employed to solve the Bloch-Torrey equations in the presence of distant-dipole fields in nuclear magnetic resonance. The procedure, although only carried out to first order in the perturbation parameter a=1/k2Dtaud, could, in principle, be generalized to higher orders. Here D is the diffusivity, taud the dipolar demagnetization time, and k is the wave vector of the spatial modulation of magnetization produced by the magnetic field gradient. The results are especially interesting for dilute binary mixtures consisting of molecular species with different diffusivities. In this case the calculated two-dimensional correlation spectroscopy revamped by asymmetric Z-gradient echo detection spectra are shown to be free from some inadequacies resulting from a simplistic application of standard approximations.     

Contrasting behavior in azide pyrolyses: an investigation of the thermal decompositions of methyl azidoformate, ethyl azidoformate and 2-azido-N, N-dimethylacetamide by ultraviolet photoelectron spectroscopy and matrix isolation infrared spectroscopy

The thermal decompositions of methyl azidoformate (N3COOMe), ethyl azidoformate (N3COOEt) and 2-azido-N,N-dimethylacetamide (N3CH2CONMe2) have been studied by matrix isolation infrared spectroscopy and real-time ultraviolet photoelectron spectroscopy. N2 appears as an initial pyrolysis product in all systems, and the principal interest lies in the fate of the accompanying organic fragment. For methyl azidoformate, four accompanying products were observed: HNCO, H2CO, CH2NH and CO2, and these are believed to arise as a result of two competing decomposition routes of a four-membered cyclic intermediate. Ethyl azidoformate pyrolysis yields four corresponding products: HNCO, MeCHO, MeCHNH and CO2, together with the five-membered-ring compound 2-oxazolidone. In contrast, the initial pyrolysis of 2-azido-N,N-dimethyl acetamide, yields the novel imine intermediate Me2NCOCH=NH, which subsequently decomposes into dimethyl formamide (HCONMe2), CO, Me2NH and HCN. This intermediate was detected by matrix isolation IR spectroscopy, and its identity confirmed both by a molecular orbital calculation of its IR spectrum, and by the temperature dependence and distribution of products in the PES and IR studies. Mechanisms are proposed for the formation and decomposition of all the products observed in these three systems, based on the experimental evidence and the results of supporting molecular orbital calculations.     

Durbin-Watson statistic as a morphological estimator of information content

The present work proposes a new approach for the evaluation of the information content in latent variables, and therefore, for the determination of the regression model dimensionality. Several examples are provided, using simulated, real-world, and reference datasets. The results showed that the application of the Durbin-Watson (DW) criterion could be used for the determination of the number of latent variables. Moreover, the method is straightforward in its implementation and could help in the understanding of model behaviour, particularly in complex datasets. A comparison is made with cross-validation techniques for the case of reference datasets, showing the potential of the Durbin-Watson criterion in the characterisation of the regression model. The advantages and disadvantages of this procedure (compared to cross-validation) are discussed. The properties of the information content of the regression vectors (loadings p, w and b vectors) are shown as well as how to use them for the current purpose.     

Applicability of Microaerobic Technology to Enhance BTEX Removal from Contaminated Waters

As the addition of low concentrations of oxygen can favor the initial degradation of benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds, this work verified the applicability of the microaerobic technology to enhance BTEX removal in an anaerobic bioreactor supplemented with high and low co-substrate (ethanol) concentrations. Additionally, structural alterations on the bioreactor microbiota were assessed throughout the experiment. The bioreactor was fed with a synthetic BTEX-contaminated water (~ 3 mg L^?1 of each compound) and operated at a hydraulic retention time of 48 h. The addition of low concentrations of oxygen (1.0 mL min^?1 of atmospheric air at 27 °C and 1 atm) assured high removal efficiencies (> 80%) for all compounds under microaerobic conditions. In fact, the applicability of this technology showed to be viable to enhance BTEX removal from contaminated waters, especially concerning benzene (with a 30% removal increase), which is a very recalcitrant compound under anaerobic conditions. However, high concentrations of ethanol adversely affected BTEX removal, especially benzene, under anaerobic and microaerobic conditions. Finally, although bacterial community richness decreased at low concentrations of ethanol, in general, the bioreactor microbiota could deal with the different operational conditions and preserved its functionality during the whole experiment.