Infinite dilution activity coefficient and vapour liquid equilibrium measurements for dimethylsulphide and tetrahydrothiophene with hydrocarbons

The activity coefficients at infinite dilution (γ^∞) of dimethylsulphide (DMS) in four hydrocarbon solvents were measured using the dilutor technique at temperatures between 288 K and 303 K. The four hydrocarbons were hexane, 1-hexene, 2,2,4-trimethylpentane and 2,4,4-trimethyl-1-pentene. The dilutor technique is based on the stripping of the highly diluted solute, i.e. DMS, by a constant flow of inert gas. The gas composition was analysed by gas chromatography and the rate of solute removal was calculated from the area of the peaks.     

Characterisation of proanthocyanidin aglycones and glycosides from rose hips by high-performance liquid chromatography-mass spectrometry, and their rapid quantification together with vitamin C

Fifteen individual proanthocyanidin aglycones and 19 glycosides, together with a complex mixture of chromatographically non-separated tetra- to octameric proanthocyanidin glycosides were detected--the non-separated glycosides being novel natural products--and characterised from dog rose hips using high-performance liquid chromatography-electrospray ionisation mass spectrometry (HPLC-ESI-MS). Along with these phenolics, a 50% aqueous ethanol extract of rose hips was found to contain high levels of Vitamin C. A simple and rapid HPLC method assisted by diode array detection for the estimation of the total concentration of proanthocyanidin aglycones and glycosides, as well as Vitamin C, in rose hip extracts was developed.     

Extreme Covariant Observables for Type I Symmetry Groups

The structure of covariant observables—normalized positive operator measures (POMs)—is studied in the case of a type I symmetry group. Such measures are completely determined by kernels which are measurable fields of positive semidefinite sesquilinear forms. We produce the minimal Kolmogorov decompositions for the kernels and determine those which correspond to the extreme covariant observables. Illustrative examples of the extremals in the case of the Abelian symmetry group are given. Dedicated to Pekka J. Lahti in honor of his sixtieth birthday     

Phase equilibria on binary systems containing diethyl sulfide

Isothermal vapor-liquid equilibrium (VLE) of the following systems was measured with a recirculation still: diethyl sulfide + ethanol at 343.15 K, diethyl sulfide + 1-propanol at 358.15 K, and diethyl sulfide + propyl acetate at 363.15 K. Diethyl sulfide + ethanol at 343.15 K and diethyl sulfide + 1-propanol at 358.15 K systems exhibit positive deviation from Raoult's law, whereas diethyl sulfide + propyl acetate at 363.15 K system exhibits only slight positive deviation from Raoult's law. A maximum pressure azeotrope was found in the systems diethyl sulfide + ethanol (x₁ = 0.372, P = 88.4 kPa, T = 343.15 K) and diethyl sulfide + 1-propanol (x₁ = 0.640, P = 96.8 kPa, T = 358.15 K). No azeotropic behavior was found in diethyl sulfide + propyl acetate system at 363.15 K. The experimental results were correlated with the Wilson model and compared to COSMO-SAC predictive model. Liquid and vapor phase compositions were determined with gas chromatography. All measured data sets passed the thermodynamic consistency tests. The activity coefficients at infinite dilution are also presented.     

Phase equilibria on five binary systems containing 1-butanethiol and 3-methylthiophene in hydrocarbons

Isothermal vapor–liquid equilibrium (VLE) of the following systems was measured with a recirculation still: 1-butanethiol + methylcyclopentane at 343.15 K, 1-butanethiol + 2,2,4-trimethylpentane at 368.15 K, 3-methylthiophene + toluene at 383.15 K, 3-methylthiophene + o-xylene at 383.15 K, and 3-methylthiophene + 1,2,4-trimethylbenzene at 383.15 K. 1-Butanethiol + methylcyclopentane and 1-butanethiol + 2,2,4-trimethylpentane systems exhibit positive deviation from Raoult's law, whereas systems containing 3-methylthiophene in aromatic hydrocarbons exhibit only slight positive deviation from Raoult's law. A maximum pressure azeotrope was found in the system 1-butanethiol + 2,2,4-trimethylpentane (x₁ = 0.548, P = 100.65 kPa, T = 368.15 K). The experimental results were correlated with the Wilson model and compared with original UNIFAC and COSMO-SAC predictive models. Raoult's law can be used to describe the behavior of 3-methylthiophene in aromatic hydrocarbons at the experimental conditions in this work. Liquid and vapor-phase composition were determined with gas chromatography. All measured data sets passed the thermodynamic consistency tests applied. The activity coefficients at infinite dilution are also presented.     

First evidence of hexameric and heptameric ellagitannins in plants detected by liquid chromatography/electrospray ionisation mass spectrometry

Ellagitannins are bioactive plant polyphenols of which more than 500 individual compounds have been identified from plants. An ellagitannin-rich fraction was isolated by Sephadex LH-20 from Oenothera biennis (common evening primrose) leaves and roots and analysed by high-performance liquid chromatography/diode-array detection coupled to high-resolution mass spectrometry with an electrospray ionisation interface. The high-molecular mass ellagitannins were characterised by their UV spectra, molecular masses and mass spectral fragments. In addition to the previously reported dimers and trimers, an entire series of oligomeric ellagitannins from dimers to heptamers was characterised in both roots and leaves of O. biennis. This is the first report of natural ellagitannins larger than pentamers.     

Solubility of carbon dioxide in aqueous solutions of diisopropanolamine and methyldiethanolamine

The solubility of carbon dioxide in aqueous solutions of alkanolamines was measured by means of two experimental methods. The solubility of carbon dioxide was measured at 298 K with a static total pressure apparatus in solutions of water + diisopropanolamine (DIPA) having mass fraction of DIPA equal to 10.1%, 11.0% and 33.9%. The density of the water + DIPA solution was measured continuously during the experiments to investigate the changes in density introduced by the absorption of carbon dioxide. A correlation for the density of CO₂-loaded aqueous solutions of DIPA is presented.     

Characterization of Natural and Alkaline-Oxidized Proanthocyanidins in Plant Extracts by Ultrahigh-Resolution UHPLC-MS/MS

In this study, we analyzed the proanthocyanidin (PA) composition of 55 plant extracts before and after alkaline oxidation by ultrahigh-resolution UHPLC-MS/MS. We characterized the natural PA structures in detail and studied the sophisticated changes in the modified PA structures and the typical patterns and models of reactions within different PA classes due to the oxidation. The natural PAs were A- and B-type PCs, PDs and PC/PD mixtures. In addition, we detected galloylated PAs. B-type PCs in different plant extracts were rather stable and showed no or minor modification due to the alkaline oxidation. For some samples, we detected the intramolecular reactions of PCs producing A-type ether linkages. A-type PCs were also rather stable with no or minor modification, but in some plants, the formation of additional ether linkages was detected. PAs containing PD units were more reactive. After alkaline oxidation, these PAs or their oxidation products were no longer detected by MS even though a different type and/or delayed PA hump was still detected by UV at 280 nm. Galloylated PAs were rather stable under alkaline oxidation if they were PC-based, but we detected the intramolecular conversion from B-type to A-type. Galloylated PDs were more reactive and reacted similarly to nongalloylated PDs.     

Chemical ecology of tannins: recent developments in tannin chemistry reveal new structures and structure-activity patterns

Tannins are chemically complex plant polyphenols and only little is known of their true molecule-specific anti-herbivore activities. Here we will show that modern tannin chemistry is able to reveal fully new types of tannins in plants together with new types of biological activities for the tannins. Most of these new findings relate to ellagitannins, one of the least studied and underestimated classes of bioactive plant polyphenols.     

Interaction of cytochrome c with 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine: evidence for acyl chain reversal

The conformational dynamics of the oxidatively modified phospholipid 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC) were assessed by observing by fluorescence energy transfer the association of the water-soluble cationic protein cytochrome c with micelles composed of this lipid. In keeping with reversal of the azelaoyl chain so as to expose its carboxyl function on the micelle surface, cytochrome c bound avidly to the micelles. In contrast, the aldehyde group bearing 1-palmitoyl-2-(9'-oxo-nonanoyl)-sn-glycero-3-phosphocholine (PoxnoPC) interacted only weakly. While the physiological significance of the above interaction is uncertain, our results demonstrate that oxidative damage alters the physical properties of lipid bilayers, involving enrichment of the polar moieties of oxidatively modified lipid chains within the membrane surface.