Structure de la rubranine, chalcone isolee de l'Aniba rosaeodora ducke

Rubranine, C₂₅H₂₆O₄ is a chalcone isolated from Aniba rosaeodora DUCKE. It has been established that its structure results from the condensation of a C-10 unit with 2,4,6-trihydroxychalcone.     

A contribution to the modeling of metal foams on the mesoscale

Due to their useful properties in lightweight construction and due to their excellent behavior in energy absorption for example in crash mechanics, metal foams became an interesting, often utilized and investigated material. For the determination of the mechanical properties of foams without the help of expensive experiments, a way for computing these properties is searched. The problem in doing so is that foams can be composed out of randomly distributed edges and faces with varying thickness and of other inhomogeneities on the mesoscale like imperfections. The goal in this paper is, to investigate the influence of these irregularities on the mechanical, linear elastic properties of a metal foam on the macroscale and to determine the size of a representative volume element, for which the irregularities on the mesoscale do not have a great influence on the linear elastic properties. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Surface plasmons mediated energy transfer from a semiconductor quantum well to an organic overlayer

We consider the resonant energy transfer from a two-dimensional Wannier exciton (donor) to a Frenkel exciton of a molecular crystal overlayer (acceptor) when the active media are separated by a metallic layer, possibly an electrode. We characterize the effect of the surface plasmon on this process. Using realistic values of material parameters, we show that it is possible to increase the transfer rate within typically a factor of 5, with a 1.25 efficiency enhancement (up to a factor of 44 with ten times larger efficiency according to geometrical configuration). Foreseeing applications to light emitting diode, we then take into account the quenching of the organic luminescence due to the proximity to the metal. The latter is significant and affect negatively the total internal efficiency that we discuss for different geometries.     

Targeted phase II metabolites profiling as new screening strategy to investigate natural steroid abuse in animal breeding

The use of steroid hormones as growth promoters in cattle is banned within the European Union since 1988 but can still be fraudulently employed in animal breeding farms for anabolic purposes. While efficient targeted confirmatory methods have been implemented in control laboratories for many years, fast and reliable screening methods are still required, especially in the case of natural hormones abuse, but more globally for new "fishing" strategies allowing to reveal the use of even unknown anabolic agents. The development of focused profiling or untargeted metabolomic approaches is thus emerging in this context. The present study was a focused profiling study using steroids phase II metabolites, with the aim to get a better understanding of the steroid metabolism disruptions after exogenous administration of androstenedione and finally reveal potential biomarkers signing its administration. A sample preparation procedure was first developed, based on a separation of 31 glucuronide and sulphate conjugate compounds using an anion exchange SPE system. Each fraction was then analysed by UPLC-MS/MS in MRM mode showing a rapid (between 4h and 4 days after treatment) and huge excretion of several direct metabolites of androstenedione such as etiocholanolone-glucuronide or epiandrosterone-sulphate.     

3,4-Methylenedioxypyrovalerone (MDPV) and metabolites quantification in human and rat plasma by liquid chromatography–high resolution mass spectrometry

Synthetic cathinones are recreational drugs that mimic the effects of illicit stimulants like cocaine, amphetamine or Ecstasy. Among the available synthetic cathinones in the United States, 3,4-methylenedioxypyrovalerone (MDPV) is commonly abused and associated with dangerous side effects. MDPV is a dopamine transporter blocker 10-fold more potent than cocaine as a locomotor stimulant in rats. Previous in vitro and in vivo studies examining MDPV metabolism reported 3,4-dihydroxypyrovalerone (3,4-catechol-PV) and 4-hydroxy-3-methoxypyrovalerone (4-OH-3-MeO-PV) as the two primary metabolites. We developed and validated a liquid chromatography–high resolution mass spectrometry method to quantify MDPV and its primary metabolites in 100 μL human and rat plasma. Plasma hydrolysis was followed by protein precipitation before analysis. Limits of detection were 0.1 μg L⁻¹, with linear ranges from 0.25 to 1000 μg L⁻¹. Process efficiency, matrix effect, total imprecision (%CV) and accuracy (%target) were 36–93%, from −8 to 12%, 2.1 to 7.3% and 86 to 109%, respectively. MDPV and metabolites were stable at room temperature for 24 h, 4 °C for 72 h and after 3 freeze-thaw cycles with less than 10% variability. Human-rat plasma cross validation demonstrated that rat plasma could be accurately quantified against a human plasma calibration curve. As proof of this method, rat plasma specimens were analyzed after intraperitoneal and subcutaneous dosing with MDPV (0.5 mg kg⁻¹). MDPV, 3,4-catechol-PV and 4-OH-3-MeO-PV concentrations ranged from not detected to 107.5 μg L⁻¹ prior to and up to 8 h after dosing. This method provides a simultaneous quantification of MDPV and two metabolites in plasma with good selectivity and sensitivity.     

Effect of different proteases on bitterness of hemoglobin hydrolysates

Hemoglobin was hydrolyzed by several enzymes (Proctase, Alcalase, Neutrase, papain). Hydrolysates were analyzed (degree of hydrolysis, gel permeation on Superose 12 column, tasting) and fractionated by ultrafiltration and 2-butanol extraction. The bitter peptides were isolated and identified. The results were compared with those already obtained with peptic hemoglobin hydrolysates. All the findings were confirmed. Ultrafiltration concentrated bitter compounds in the fraction corresponding to 500–5000 Da, and these compounds were selectively extracted by 2-butanol. All the bitter peptides belonged to the same fragment of the Β-chain of bovine hemoglobin. Finally, the use of a Superose 12 Chromatographic column for easy detection of bitter hydrolysates without sensory analysis could be generalized for hemoglobin hydrolysates.