Antioxidant activity and total phenols from the methanolic extract of Miconia albicans (Sw.) Triana leaves

Miconia is one of the largest genus of the Melastomataceae, with approximately 1,000 species. Studies aiming to describe the diverse biological activities of the Miconia species have shown promising results, such as analgesic, antimicrobial and trypanocidal properties. M. albicans leaves were dried, powdered and extracted to afford chloroformic and methanolic extracts. Total phenolic contents in the methanolic extract were determined according to modified Folin-Ciocalteu method. The antioxidant activity was measured using AAPH and DPPH radical assays. Chemical analysis was performed with the n-butanol fraction of the methanolic extract and the chloroformic extract, using different chromatographic techniques (CC, HPLC). The structural elucidation of compounds was performed using 500 MHz NMR and HPLC methods. The methanolic extract showed a high level of total phenolic contents; the results with antioxidant assays showed that the methanolic extract, the n-butanolic fraction and the isolated flavonoids from M. albicans had a significant scavenging capacity against AAPH and DPPH. Quercetin, quercetin-3-O-glucoside, rutin, 3-(E)-p-coumaroyl-α-amyrin was isolated from the n-butanolic fraction and α-amyrin, epi-betulinic acid, ursolic acid, epi-ursolic acid from the chloroformic extract. The results presented in this study demonstrate that M. albicans is a promising species in the search for biologically active compounds.     

Computer modelling of the reduction of rare earth dopants in barium aluminate

Long lasting phosphorescence in barium aluminates can be achieved by doping with rare earth ions in divalent charge states. The rare earth ions are initially in a trivalent charge state, but are reduced to a divalent charge state before being doped into the material. In this paper, the reduction of trivalent rare earth ions in the BaAl₂O₄ lattice is studied by computer simulation, with the energetics of the whole reduction and doping process being modelled by two methods, one based on single ion doping and one which allows dopant concentrations to be taken into account. A range of different reduction schemes are considered and the most energetically favourable schemes identified.     

Influence of co‐dopant in the europium reduction in SrAl2O4 host

Xerogels of strontium chlorate and aluminium chlorate doped with europium (un‐co‐doped) and co‐doped with rare earth ions (Ln = Gd, Dy, Er and Y) were prepared using the proteic sol–gel route. Synchrotron radiation was used to investigate the effect of different co‐dopants on the Eu³⁺→ Eu²⁺ reduction process during the synthesis of the samples. Samples were excited at the Eu L_III‐edge and the XANES regions were analyzed. The results suggest that some of the Eu ions can be stabilized in the divalent state and that it is difficult to completely reduce Eu³⁺ to Eu²⁺ during thermal treatment. The mechanisms of the Eu reduction processes are explained by a proposed model based on the incorporation of charge‐compensation defects.     

Fast LC–MS Electrospray Ionization for the Quantification of Digoxin in Human Plasma and Its Application to Bioequivalence Studies

A fast, sensitive and specific liquid chromatography-mass spectrometry method has been developed for quantification of digoxin in human plasma. The method was optimized to bioequivalence studies aiming higher sensitivity and selectivity than previously published methods, in addition to shorter run time allowing high-throughput sample analyses from volunteers. Chromatographic separation was achieved by an RP-18e column hyphenated to an API 5000 mass spectrometer system set at negative electrospray ionization and operating in the MRM mode. Calibration curve was linear over a wide range of concentration (50.0–6000.0 pg mL⁻¹), with the lower limit of quantification at 50.0 pg mL⁻¹ and without interfering peaks at the retention time of digoxin (2.09 min). Dexamethasone was used as internal standard and samples were cleaned up by liquid-liquid extraction obtaining a mean recovery of 73.8%. Validation results confirmed inter-batch accuracy (−8.66 to 5.78%), precision (4.1–10.6%) and stability, in accordance with the U.S. Food and Drug Administration and the Brazilian National Health Surveillance Agency guidelines. The developed analytical method could be successfully applied to a single oral dose (0.25 mg), one-way, randomized, two-sequence, crossover bioequivalence study validating, up to date, the fastest analysis and the most sensitive and specific method already published for digoxin quantification.     

Magnon excitation by spin injection in thin Fe/Cr/Fe films

The technique of Brillouin light scattering is used to observe strong excitation of magnons in antiferromagnetically coupled trilayers of Fe/Cr/Fe at room temperature. The magnons are driven out of equilibrium by a microwave current applied in the trilayer through point contacts. The magnitude of the scattering intensity is investigated as a function of the magnon wave number and applied magnetic field. Confirming recent theoretical predictions, the observations provide strong evidence of electronic spin injection in the rf driving field.     

Characterization of βN-Octadecanoyl-5-hydroxytryptamide Anti-Inflammatory Effect

Background: N-octadecanoyl-5-hydroxytryptamide (C₁₈-5HT) is an amide that can be obtained by the coupling of serotonin and octadecanoic acid. This study aims to characterize the in vivo and in vitro anti-inflammatory activity of C₁₈-5HT. Methods: A subcutaneous air pouch model (SAP) was used. The exudates were collected from SAP after carrageenan injection to assess cell migration and inflammatory mediators production. RAW 264.7 cells were used for in vitro assays. Results: C₁₈-5HT significantly inhibited leukocyte migration into the SAP as well as nitric oxide (NO) and cytokines production and protein extravasation. We also observed an reduction in some cytokines and an increase in IL-10 production. Assays conducted with RAW 264.7 cells indicated that C₁₈-5HT inhibited NO and cytokine produced. Conclusions: Taken together, our data suggest that C₁₈-5HT presents a significant effect in different cell types (leukocytes collected from exudate, mainly polumorphonuclear leukocytes and cell culture macrophages) and is a promising compound for further studies for the development of a new anti-inflammatory drug.     

Evaluation of alignment methods and data pretreatments on the determination of the most important peaks for the discrimination of coffee varieties Arabica and Robusta using gas chromatography-mass spectroscopy

Coffee samples were analyzed by GC/MS in order to determine the most important peaks for the discrimination of the varieties Arabica and Robusta. The resulting peak tables from chromatographic analysis were aligned and pretreated before being submitted to multivariate analysis. A rapid and easy-to-perform peak alignment procedure, which does not require advanced programming skills to use, was compared with the tedious manual alignment procedure. The influence of three types of data pretreatment, normalization, logarithmic and square root transformations and their combinations, on the variables selected as most important by the regression coefficients of partial least squares-discriminant analysis (PLS-DA), are shown. Test samples different from those used in the calibration and comparison with the substances already known as being responsible for Arabica and Robusta coffees discrimination were used to determine the best pretreatments for both datasets. The data pretreatment consisting of square root transformation followed by normalization (RN) was chosen as being the most appropriate. The results obtained showed that the much quicker automated aligned method could be used as a substitute for the manually aligned method, allowing all the peaks in the chromatogram to be used for multivariate analysis.     

A Polar Representation and the Morse Index Theorem

In this Letter we study the behavior of the eigenvalues of an operator defined by the action associated to a generic quadratic time-dependent Hamiltonian. This is done using a polar representation of the solutions of the corresponding linear Hamiltonian system. A proof of the Morse index theorem is given.