Qualitative and Quantitative Analysis of 17 Different Types of Tetra- and Pentacyclic Triterpenic Acids in Boswellia papyrifera by a Semi-Automatic Homomodal 2D HPLC method

A semi-automatic two dimensional high-performance liquid chromatography (HPLC) gradient method with photo diode array detection was developed, capable of separating and quantifying up to 17 different triterpenic acids in the gum resin of the frankincense species Boswellia papyrifera. The here reported quantitation of 14 of the possible 17 compounds contains boswellic, tirucallic and lupeolic acids. All compounds were isolated from B. papyrifera and used as external standards. Quantitation of these compounds was performed after minimizing the matrix by liquid?Cliquid separation, using alkaline, acidic and organic media to separate the acids from interfering matrix compounds. Therefore, two different extraction procedures were tested, giving two different extraction profiles. Within the first run (1st dimension) 13 compounds could be quantified. Quantitation of ??-boswellic acid, which was proved to elute as inhomogeneous peak, was achieved by introduction of a second dimension, leading to a fully validated semi-automatic homomodal 2D chromatography. The method is applicable for determination of compounds occurring in different types of frankincense and their pharmaceutical products. It also can be applied to distinguish between different kinds of frankincense. Moreover, it is the first published method feasible of separating and quantifying five different types of tirucallic acids.     

The discovery of Kv1.5 blockers as a case study for the application of virtual screening approaches

Different virtual screening techniques are available as alternatives to high throughput screening. These different techniques have been rarely used together on the same target. We had the opportunity to do so in order to discover novel blockers of the voltage-dependent potassium channel Kv1.5, a potential target for the treatment of atrial fibrillation. Our corporate database was searched, using a protein-based pharmacophore, derived from a homology model, as query. As a result, 244 molecules were screened in vitro, 19 of them (7.8%) were found to be active. Five of them, belonging to five different chemical classes, exhibited IC50 values under 10 microM. The performance of this structure-based virtual screening protocol has been compared with those of similarity and ligand-based pharmacophore searches. The analysis of the results supports the conventional wisdom of using as many virtual screening techniques as possible in order to maximize the chance of finding as many chemotypes as possible.     

Equilibrium Topology and Partial Inversion of Janus Drops: A Numerical Analysis

The equilibrium topology of an aqueous Janus emulsion of two oils, O1 and O2, with water, W, [(O1+O2)/W], is numerically evaluated with the following realistic interfacial tensions (γ): γ_O2/W=5 mN m⁻¹, γ_O1/O2=1 mN m⁻¹, and γ_O1/W varies within the range 4–5 mN m⁻¹, which is the limiting range for stable Janus drop topology. The relative significance of the two independently pivotal factors for the topology is evaluated, that is, the local equilibrium at the line of contact between the three liquids and the volume fraction of the two dispersed liquids within the drop. The results reveal a dominant effect of the local equilibrium on the fraction of the O2 drop surface that is covered by O1. In contrast, for a constant volume of O2, the impact of the interfacial tension balance on the limit of the coverage is modest for an infinite volume of O1. Interestingly, when the O1 volume exceeds this value, an emulsion inversion occurs, and the O1 portion of the (O1+O2)/W topology becomes a continuous phase, generating a (W+O2)/O1 Janus configuration.     

Methods of multivariate data analysis applied to the investigation of fen soils

Fen soils from two sites of the Rhin-Havel-Luch, a peatland in the north-east of Germany, have been investigated. The samples have been collected in two horizons, representing different degrees of degradation and mineralisation of peat. Gravimetric measurements, energy dispersive X-ray fluorescence (EDXRF), elemental analysis, and ¹H low resolution nuclear magnetic resonance (LR-NMR) of the fen soil samples have been performed. By multivariate analysis of all the experimental data, especially by the principal component analysis (PCA) and by the cluster analysis, respectively, it was possible to classify the fen soils, to identify their characteristic properties, to detect temporal and local variations, and to prove representative field sampling. Furthermore, the correlation between variables of the applied analytical methods could be interpreted in context to the composition of fen soils and mutual influences of their properties.     

Synthesis of Benzaldehyde‐Functionalized Glycans: A Novel Approach Towards Glyco‐SAMs as a Tool for Surface Plasmon Resonance Studies

In recent years the interest in tools for investigating carbohydrate–protein (CPI) and carbohydrate‐carbohydrate interactions (CCI) has increased significantly. For the investigation of CPI and CCI, several techniques employing different linking methods are available. Surface plasmon resonance (SPR) imaging is a most appropriate tool for analyzing the formation of self‐assembled monolayers (SAM) of carbohydrate derivatives, which can mimic the glycocalyx. In contrast to the SPR imaging methods used previously to analyze CPI and CCI, the novel approach reported herein allows a facile and rapid synthesis of linker spacers and carbohydrate derivatives and enhances the binding event by controlling the amount and orientation of ligand. For immobilization on biorepulsive amino‐functionalized SPR chips by reductive amination, diverse aldehyde‐functionalized glycan structures (glucose, galactose, mannose, glucosamine, cellobiose, lactose, and lactosamine) have been synthesized in several facile steps that include olefin metathesis. Effective immobilization and the first binding studies are presented for the lectin concanavalin A.     

Sample cleanup-free determination of mycophenolic acid and its glucuronide in serum and plasma using the novel technology of ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry

Mycophenolic acid (MPA) is an immunosuppressant drug which powerfully inhibits lymphocyte proliferation. Since the early 1990s it has been used to prevent rejection in organ transplantation. The requirement of therapeutic drug monitoring shown in previous studies raises the necessity of acquiring accurate and sensitive methods to measure MPA and its major metabolite mycophenolic acid glucuronide (MPAG).The authors developed a sample cleanup-free, rapid, and highly specific method for simultaneous measurement of MPA and MPAG in human plasma and serum using the novel technology of ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry. MPA- and MPAG-determinations were performed during a 2.0-min run time. Multiple calibration curves for the analysis of MPA and MPAG exhibited consistent linearity and reproducibility in the range of 0.05-100 (r > 0.999) mg L⁻¹ and 4-4000 mg L⁻¹ (r > 0.999), respectively. Limits of Detection were 0.014 mg L⁻¹ for MPA and 1.85 mg L⁻¹ for MPAG. Lower Limits of Quantification were 0.05 mg L⁻¹ for MPA and 2.30 mg L⁻¹ for MPAG. Interassay imprecision was <10% for both substances. Mean recovery was 103.6% (range 78.1-129.7%) for MPA and 111.1% (range 73.0-139.6%) for MPAG. Agreement was good for MPA and MPAG between the presented method and a validated HPLC-MS/MS method. The Passing-Bablok regression line for MPA and MPAG was HPLC-MS/MS = 1.14 UPLC-MS/MS—0.14 [mg L⁻¹], r = 0.96, and HPLC-MS/MS = 0.77 UPLC-MS/MS + 0.50 [mg L⁻¹], r = 0.97, respectively. This sample cleanup-free and robust LC-MS/MS assay facilitates the rapid, accurate and simultaneous determination of MPA and MPAG in human body fluids.     

Nickel and palladium complexes of enolatefunctionalised N-heterocyclic carbenes

The reaction of chloroethyltrimethylsilylether with 1-methylimidazole furnishes an ionic liquid that undergoes methanolysis to crystalline 2-hydroxyethylimidazolium chloride (crystal structure presented). Conversion to defined hydroxyethylimidazol-2-ylidene nickel complexes failed, but was accomplished with 1-methyl-3-acetophenyl-imidazolium bromide. The bis(NHC^⋂O⁻) nickel(II) chelate is formed, rather than a methallylnickel monochelate, but with nickelocene a monochelate NiCp complex was detected. The bulky 1-(2,6-diisopropylphenyl)-3-(2’-phenyl-enolato)-imidazol-2-ylidene allylpalladium chloride was obtained in pure form. Attempts to generate catalysts for ethylene oligomerization by in situ techniques have failed so far whereas P^⋂O⁻ ligands, comparable by the P-C diagonal relationship, provide active catalysts.      

A CE‐based assay for human protein kinase CK2 activity measurement and inhibitor screening

A new assay for protein kinase CK2 activity determination based on the quantification of a phosphorylated substrate was developed. The common CK2 substrate peptide RRRDDDSDDD, conjugated with the fluorophore 5‐[(2‐aminoethyl)amino]naphthalene‐1‐sulfonic acid at the C‐terminus served as the analyte. By means of CZE using 2 mol/L acetic acid as electrolyte and UV detection at 214 nm, the non‐phosphorylated and the phosphorylated peptide variants could be resolved within 6 min from a complex assay mixture. By this means, activity of human CK2 could be monitored by a kinetic, as well as an endpoint, method. Inhibition of human recombinant CK2 holoenzyme by 6‐methyl‐1,3,8‐trihydroxyanthraquinone and 4,5,6,7‐tetrabromobenzotriazole resulted in IC₅₀ values of 1.33 and 0.27 μM, respectively, which were similar to those obtained with the standard radiometric assay. These results suggest that the CE/UV strategy described here is a straightforward assay for CK2 inhibitor testing.