Aqueous two-phase systems: An efficient,environmentally safe and economically viable method for purification of natural dye carmine

Partition of the natural dye carmine has been studied in aqueous two-phase systems prepared by mixing aqueous solutions of polymer or copolymer with aqueous salt solutions (Na₂SO₄ and Li₂SO₄). The carmine dye partition coefficient was investigated as a function of system pH, polymer molar mass, hydrophobicity, system tie-line length and nature of the electrolyte. It has been observed that the carmine partition coefficient is highly dependent on the electrolyte nature and pH of the system, reaching values as high as 300, indicating the high potential of the two-phase extraction with ATPS in the purification of carmine dye. The partition relative order was Li₂SO₄ ? Na₂SO₄. Carmine molecules were concentrated in the polymer-rich phase, indicating an enthalpic specific interaction between carmine and the pseudopolycation, which is formed by cation adsorption along the macromolecule chain. When the enthalpic carmine–pseudopolycation interaction decreases, entropic forces dominate the natural dye-transfer process, and the carmine partitioning coefficient decreases. The optimization of the extraction process was obtained by a central composite face-centered (CCF) design. The CCF design was used to evaluate the influence of Li₂SO₄ and PEO 1500 concentration and of the pH on the partition coefficient of carmine. The conditions that maximize the partition of carmine into the top phase were determined to be high concentrations of PEO and Li₂SO₄ and low pH values within the ranges studied.     

Microwave-assisted digestion procedures for biological samples with diluted nitric acid: Identification of reaction products

Microwave-assisted sample preparation using diluted nitric acid solutions is an alternative procedure for digesting organic samples. The efficiency of this procedure depends on the chemical properties of the samples and in this work it was evaluated by the determination of crude protein amount, fat and original carbon. Soybeans grains, bovine blood, bovine muscle and bovine viscera were digested in a cavity-microwave oven using oxidant mixtures in different acid concentrations. The digestion efficiency was evaluated based on the determination of residual carbon content and element recoveries using inductively coupled plasma optical emission spectrometry (ICP OES). In order to determine the main residual organic compounds, the digests were characterized by nuclear magnetic resonance (¹H NMR). Subsequently, studies concerning separation of nitrobenzoic acid isomers were performed by ion pair reversed phase liquid chromatography using a C18 stationary phase, water:acetonitrile:methanol (75:20:5, v/v/v) + 0.05% (v/v) TFA as mobile phase and ultraviolet detection at 254 nm. Sample preparation based on diluted acids proved to be feasible and a recommendable alternative for organic sample digestion, reducing both the reagent volumes and the variability of the residues as a result of the process of decomposition. It was shown that biological matrices containing amino acids, proteins and lipids in their composition produced nitrobenzoic acid isomers and other organic compounds after cleavage of chemical bonds.     

Ultrastructural and biochemical changes of the medial pterygoid muscle induced by unilateral exodontia

The aim of the present study was to investigate the histological, biochemical and ultrastructural effects of occlusal alteration induced by unilateral exodontia on medial pterygoid muscle in guinea pigs, Cavia porcellus. Thirty (n=30) male guinea pigs (450g) were divided into two groups: experimental-animals submitted to exodontia of the left upper molars, and sham-operated were used as control. The duration of the experimental period was 60 days. Medial pterygoid muscles from ipsilateral and contralateral side were analyzed by histological (n=10), histochemical (n=10), and ultrastructural (n=10) methods. The data were submitted to statistical analysis. When the ipsilateral side was compared to the control group, it showed a significantly shorter neuromuscular spindle length (P<0.05), lower oxidative metabolic activity, and microvessel constriction, in spite of the capillary volume and surface density were not significantly different (P>0.05). In the contralateral side, the neuromuscular spindles showed significantly shorter length (P<0.05), the fibers reflected a higher oxidative capacity, the blood capillaries showed endothelial cell emitting slender sprouting along the pre-existing capillary, and significantly higher blood capillary surface density, and volume density (V(v)=89% Mann-Whitney test, P<0.05). This finding indicated a complex morphological and functional medial pterygoid muscle adaptation to occlusal alteration in this experimental model. Considering that neuromuscular spindles are responsible for the control of mandibular positioning and movements, the professional should consider if these changes interfere in the success of clinical procedures in medical field involving stomatognathic structures.     

A stereochemically well-defined rhodium(III) catalyst for asymmetric transfer hydrogenation of ketones

[reaction: see text] A rhodium(III) catalyst for asymmetric transfer hydrogenation of ketones has been designed. The incorporation of a tethering group between the diamino group and the cyclopentadienyl unit provides extra stereochemical rigidity. The catalyst is capable of enantioselective reduction of a range of ketones in excellent ee using formic acid/triethylamine as both the solvent and the reducing agent.     

Separation and determination of molybdenum by inductively coupled plasma optical emission spectrometry using quercetin immobilization on silica gel

A new method is described for the separation of molybdenum based on its chelation in a column packed with quercetin, immobilized on silica gel in a slightly acidic medium (pH 5.0). Recovery ranged from 95% (NIST 1515 apple leaves) to 99% (deionized, distilled water; DDW) with an absolute blank of 27.5±1.6 pg obtained for the analysis of DDW. Detection limits, absolute and relative, based on a 5.0-ml sample volume were 4.8 pg and 1 ng l⁻¹, respectively. Results are presented for molybdenum determination in two standard reference materials, NIST 1515 and NIST 1547 peach leaves, using simple calibration curves for quantification. α-Benzoinoxime was used as the eluent.     

In vitro activity of compounds isolated from Piper crassinervium against Trypanosoma cruzi

This study describes the antichagasic potential of five compounds isolated from leaves of Piper crassinervium (Piperaceae). Two prenylated benzoic acid derivatives, one prenylated hydroquinone and two flavanones, were evaluated. The in vitro trypanocidal activity was determined against epimastigote forms of Trypanosoma cruzi (Y strain), the etiologic agent of Chagas disease. The most active compound was the prenylated hydroquinone [1,4-dihydroxy-2-(3(0),7(0)-dimethyl-1(0)-oxo-2(0)-E,6(0)-octadienyl)benzene] with an IC(50) value of 6.10 microg mL(-1), which was in the same order of activity if compared with the positive control benznidazole (IC(50) = 1.60 microg mL(-1)). This is the first report of trypanocidal activity for prenylated hydroquinone and benzoic acid derivatives.     

Characterization and cytotoxicity of a benzocaine inclusion complex

Benzocaine (BZC), is a local anesthetic widely used in topical formulations as well as in throat pastilles. A disadvantage is that the compound presents low aqueous solubility. The present work describes the preparation and characterization of an inclusion complex between BZC and β-cyclodextrin (β-CD), followed by cytotoxicity assays. The association constant (Ka) was calculated using solubility isotherms, at different temperatures, and an HPLC procedure, at room temperature, employing a reverse phase C18 column, with a mobile phase consisting of water/acetonitrile. Ka obtained with solubility isotherms at temperatures of 25, 35, and 45 °C were 229.8, 317.1, and 520.3 M^?1, respectively. Employing HPLC, Ka was 38.0 M^?1. The difference in the Ka value could be explained because HPLC analyses were conducted using organic solvent, which affected the host–guest interaction. Moreover, the continuous flow could have altered the degree of association of the drug with β-CD. The BZC/CD inclusion complex was characterized using infrared spectroscopy, thermogravimetry, and X-ray diffraction. Analysis showed a good agreement with literature, suggesting that the complex was established. Cytotoxicity assays using fibroblast V79 cells showed that BZC/CD formulation was not cytotoxic, demonstrating its potential to reduce the toxicity of the anesthetic. The assays demonstrated an effective interaction between BZC and CD, and that the inclusion complex was less toxic to V79 cells than the plain BZC, turning it a good alternative to decrease its toxicity when administered to patients.     

Fluorescence spectroscopy and thermal relaxation processes of anthracenyl‐labeled polysiloxanes

A fluorescent silicone network was prepared by a hydrosilylation reaction using poly(dimethylsiloxane‐co‐methylhydrogensiloxane) terminated by dimethylhydrogensilyloxy groups, poly(dimethylsiloxane‐co‐methylvinylsiloxane) terminated by dimethylvinylsilyloxy groups and 9‐vinylanthracene, as the fluorescent group. These silicone‐based materials were strongly fluorescent. Steady state emission was a convenient technique to prove that reaction occurred, based on the blue‐shift of the emission from anthracenyl moieties compared with the 9‐vinylanthracene. Thermal transitions were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and by fluorescence spectroscopy, indicating that networks with and without lumophores had similar thermal properties. Networks with and without lumophores had the same swelling capability in toluene. Fluorescence spectroscopy was a more sensitive technique to the onset of the glass transition temperature (T = 145 K) than DSC or DMA. Nevertheless, the crystallization temperature at 192 K was determined more precisely by DSC, and the melting point at 237 K was indentified more clearly by both DSC and DMA. These three techniques provided complementary information about transitions in silicone networks. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 74–81, 2010     

Decomposition kinetics of iron (III)-diclofenac compound

Non-isothermal decomposition of iron (III)-diclofenac anhydrous salt was investigated by thermogravimetry (TG) under different conditions in opened and closed α-alumina pans under nitrogen atmosphere. To estimate the activation energy of decomposition, the Capela and Ribeiro isoconversional method was applied. The results show that due to the lid cover different activation energies were obtained. From these curves a tendency can be seen where the plots maintain the same profile for closed lids and almost run parallel to each other. Independently of the different experimental conditions no remarkably different results have been obtained.     

Palladium (II) Assisted Preparation of Methoxyarylbenzoquinones

The reaction of 2-methoxy-1,4-benzoquinone with methoxyphenolic derivative compounds obtained from wood tar constituents, assisted by palladium (II) acetate in acetic acid, allowed the preparation of five novel methoxyaryl-substituted 1,4-benzoquinones, as well as four structural isomer mixtures.