Validated HPLC method for determination of caffeine level in human plasma using synthetic plasma: application to bioavailability studies

Several high-performance liquid chromatography (HPLC) methods have been described for the determination of caffeine in human plasma. However, none have been cross validated using synthetic plasma. The present study describes a simple and reliable HPLC method for the determination of the caffeine level in human plasma. Synthetic plasma was used to construct calibration curves and quality control samples to avoid interference by caffeine commonly present in donor's human plasma. After deproteination of plasma samples with perchloric acid, caffeine and antipyrine (internal standard, IS) were separated on a Waters Atlantis C18 column using a mobile phase of 15 mM potassium phosphate (pH 3.5) and acetonitrile (83:17, v/v), and monitored by photodiode array detector, with the wavelength set at 274 nm. The relationship between caffeine concentrations and peak area ratio (caffeine-IS) was linear over the range of 0.05-20 μg/mL. Inter-run coefficient of variation was ≤ 5.4% and ≤ 6.0% and bias was ≤ 3% and ≤ 7% using human and synthetic plasma, respectively. Mean extraction recovery from human plasma of caffeine and the IS was 91% and 86%, respectively. Caffeine in human plasma was stable for at least 24 h at room temperature or 12 weeks at -20 °C, and after three freeze-thaw cycles. The method was successfully applied to monitor caffeine levels in healthy volunteers with correction of caffeine levels using the mean ratio of the slopes of the calibration's curves constructed using human and synthetic plasma.     

Kinetic properties of pancreatic and intestinal sPLA2 from chicken and mammals using the monomolecular film technique

The interfacial kinetic and binding data for the pancreatic and intestinal sPLA2 from bird and mammals show that these enzymes have dramatically different ability to bind and hydrolyse phospholipids. The main conclusions from our experimental data indicate that phosphatidylcholine monolayers (PC), in contrast to phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), were resistant to the hydrolysis by human intestinal sPLA2. Conversely, chicken intestinal sPLA2 was found to be able to hydrolyse all the phospholipids tested, including PC. The experiments show also that the interfacial penetrating ability of chicken sPLA2 (from intestine and pancreas) was higher than their mammalian's orthologs. This observation is confirmed by the activity of pancreatic chicken PLA2 measured on PC film showing that the interfacial pressure window that permits sPLA2 activity was very large, between 5 and 20 dynes cm(-1), compared with the porcine pancreatic sPLA2-IB which was inactive at pressure above 15 dynes cm(-1). In trying to establish a structure-function relationship, we examined the surface electrostatic potentials of the various sPLA2 from chicken and mammals. We reported in this study that the binding, orientation and persistence of sPLA2 at the lipid-water interface is probably governed by the electrostatic and hydrophobic forces operative at this surface. These variations argue strongly that these enzymes are not isoforms and that they are expected to have functions other than the release of lipid mediators for the biosynthesis of the eicosanoids.     

On the Projections of the Mutual Multifractal Rényi Dimensions

In this paper, we compare the mutual multifractal Rényi dimensions to the mutual multifractal Hausdorff and pre-packing dimensions. We also provide a relationship between the mutual multifractal Rényi dimensions of orthogonal projections of a couple of measures $(\mu,\nu)$ in $\mathbb{R}^n$. As an application, we study the mutual multifractal analysis of the projections of measures.     

Chromatographic analysis,antimicrobial and insecticidal activities of the essential oil of Phlomis floccosa D. Don.

The present study was conducted to investigate for the first time the chemical composition and insecticidal and antimicrobial properties of Phlomis floccosa D. Don. essential oil isolated by hydro‐distillation of its aerial parts. Qualitative and quantitative analyses of the essential oil on the basis of gas chromatography and mass spectrometry (GC/FID and GC/MS) revealed the presence of 59 organic volatiles representing 86.9% of the total constituents. The major compounds were germacrene‐D (19.7%) followed by β‐caryophyllene (15.5%), caryophyllene oxide (8.3%), hexadecenoic acid (7.9%) and carvacrol (6.1%). The broth microdilution method was conducted to test the antimicrobial activity of the essential oil against five pathogens: Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, Staphylococcus aureus, Bacillus subtilis and the yeast Candida albicans. The oil of P. floccosa D. Don. shows promising activity against the Gram‐positive bacteria S. aureus and B. subtilis and the yeast C. albicans (minimum inhibitory concentration = 625 μg.mL^?1). The effectiveness of the essential oil was assessed on both Tribolium confusum and Sitophilus zeamais pest insects and it was more pronounced against T. confusum, showing a moderate mortality of 47.5%.     

Heterocyclization of acylthiosemicarbazides

The review summarizes published data on the behavior and reactions of acylthiosemicarbazides and their derivatives, which lead to the formation of heterocyclic systems, including methods of preparation in addition to synthesis of pyrrole, thiazole, thiadiazole, thiadiazolidine, and triazole derivatives as well as fused heterocyclic compounds. J. Heterocyclic Chem., (2012).     

Une preuve alternative de l'existence d'un équilibre de Nash dans les jeux discontinus

This Note presents a theorem of the existence of the Nash equilibrium for discontinuous games in a topological vector space. We will use an assumption of better reply secure which is stronger then that of Reny. If the payoff function is upper semi-continuous, the two assumptions coincide. Our proof is simple, independent and based on a version of Fan–Browder theorem of existence of maximal element due to Deguire and Lassonde, which is extended to the non-Hausdorf case. To cite this article: J.-M. Bonnisseau et al., C. R. Acad. Sci. Paris, Ser. I 347 (2009).     

On the empirical performance of (T, s, S) heuristics

The periodic (T,s,S)$(T\text{,}s\text{,}S)$ policies have received considerable attention from the academic literature. Determination of the optimal parameters is computationally prohibitive, and a number of heuristic procedures have been put forward. However, these heuristics have never been compared in an extensive empirical study. Such an investigation on 3055 SKUs is carried out in this paper. Our study provides insights into the performance of (T,s,S)$(T\text{,}s\text{,}S)$ heuristics, also in relation to demand forecasting. The results show that Naddor’s heuristic is best able to minimize the total cost. However, the normal and power approximations achieve more efficient solutions in that backorder volumes are smaller at the same inventory levels, indicating the potentially superior performance of these methods if the balancing of holding and backorder costs can be improved. The results also show that, for all heuristics, the SBA variant of the Croston forecasting method significantly outperforms Croston as well as Single Exponential Smoothing (SES).     

Isolation and structure elucidation of a flavanone, a flavanone glycoside and vomifoliol from Echiochilon fruticosum growing in Tunisia

A flavanone and a flavanone glycoside, together with vomifoliol, have been isolated for the first time from the aerial parts of the plant Echiochilon fruticosum and identified. Their structures were established on the basis of spectroscopic measurements, mainly 2D NMR using COSY, HMQC and HMBC experiments.     

Scattering theory for a class of fermionic Pauli-Fierz models

The scattering theory for a class of fermionic Pauli-Fierz models is considered. We give a proof of the asymptotic completeness of the dynamics in the case of massive fermions. The result applied to the Hamiltonian of a quantized spin- Dirac particle interacting with an external field through a cutoff Yukawa interaction and to the Hamiltonian of a system of finitely many confined particles coupled to a fermionic field with a quadratic interaction.     

Synthesis,characterization, structures,and DFT study of zinc(II) complexes with tributylphosphine chalcogenides

Four new zinc(II) complexes of the type [ZnCl₂(n-Bu₃PE)₂] (E=O (1), S (2), Se (3), or Te (4)) have been synthesized from zinc(II) chloride and the ligands n-Bu₃PE giving yields of 56–88%. The adducts were characterized by multinuclear (³¹P, ¹³C, and ⁷⁷Se) NMR, conductivity, IR spectroscopy and by X-ray analyses. Zinc complexes 1–4 are compriseS of two ligands coordinated to the metal center in a distorted tetrahedral arrangement. The P=E bond lengths of 1.497(7) (E=O), 2.000(4) (E=S), and 2.178(2) Å (E=Se) in these complexes are slightly elongated compared to those in the free ligand. In addition, a DFT/B3LYP theoretical study on the geometry optimization of the title ligands and their zinc complexes has been carried out in order to support and complement the experimental data and to further investigate the nature of the chalcogenide-metal interaction. The results show good agreement between the experimental and theoretical data.