Mechanism of anti-inflammatory action of liquorice extract and glycyrrhizin

The antiradical activity, protective effect against lipid peroxidation of liposomal membrane, and inhibitory effect on whole blood reactive oxygen species (ROS) liberation of Glycyrrhiza glabra crude extract and glycyrrhizin, its major compound, were assessed. The liquorice extract showed significant activity in all the three assay systems used in a dose dependent manner. It displayed remarkable reactivity with free stable 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radical, inhibitory efficacy in peroxidatively damaged unilamellar dioleoyl phosphatidylcholine (DOPC) liposomes, and inhibition of ROS chemiluminescence, generated by whole blood, induced by both receptor-bypassing stimuli (PMA) and receptor operating stimuli (Opz) in the ranking order of stimuli PMA> Opz. These activities may be attributed to phenolic antioxidants involving isoflavan derivatives, coumarins and chalcones. Nonetheless, triterpene saponin glycyrrhizin exhibited no efficacy in the system of DPPH reaction and peroxidation of liposomal membrane, and negligible inhibition of chemiluminescence generated by inflammatory cells. These results indicate that the mechanism of anti-inflammatory effect of glycyrrhizin most probably does not involve ROS and this major constituent is not responsible for the inhibition effects of liquorice extract on neutrophil functions.     

Radical-scavenging activity of glutathione,chitin derivatives and their combination

Since chitosan and its amino-, cinnamo- or cinnamo-amino- derivatives are acid-soluble, the effect of acetic acid on hyaluronan (HA) macromolecules degraded by Cu(II) ions and ascorbate was examined to produce reactive oxygen species (ROS). Further, the effects of glutathione (GSH), chitosan and its derivatives, added individually or in combination, on the quenching of ROS and ABTS^˙+ cation radical were examined using rotational viscometry and ABTS assay, respectively. The results of the rotational viscometry indicated a rapid degradation of HA by ROS after the addition of acetic acid. Chitosan and its derivatives moderately decreased the rate of HA degradation, while GSH decreased the rate of HA degradation more significantly. Moreover, GSH enhanced the protection of HA macromolecules against their degradation in the presence of chitosan or its derivatives. The results of the ABTS assay confirmed the results of the rotational viscometry. The GSH in the combination with chitosan and its derivatives reduced ABTS^˙+ more intensively than when added individually.     

Dithiols as more effective than monothiols in protecting biomacromolecules from free-radical-mediated damage: in vitro oxidative degradation of high-molar-mass hyaluronan

Oxidative stress and the resulting damage to cellular and extracellular components has been observed in a variety of degenerative processes, including degenerative joint disorders, where high-molar-mass hyaluronan (HA) is often found to be massively degraded. The present study sought to test the hypothesis that dithiols are more effective in protecting biomacromolecules from free-radicalmediated damage than monothiols. The materials/thiols tested included bucillamine (BUC), dithioerythritol (DTE), dithiothreitol (DTT) and glutathione (GSH), as a reference, for their effectiveness in protecting HA from oxidative degradation induced in vitro. Since HA degradation results in a decrease in its dynamic viscosity, rotational viscometry was applied to follow HA oxidative degradation. The free-radical-scavenging activities of the thiols tested were determined by 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (DPPH) assays. It was found that all the dithiols in the concentration range tested protected HA from the oxidative degradation. On the other hand, monothiol GSH exerted protection only at high concentrations (10 μmol L^?1 and 100 μmol L^?1) and 1 μmol L^?1 of GSH even exhibited a prodegradative effect. The ABTS assay revealed free-radical scavenging activities in the following order: BUC, DTT, DTE, GSH, and that of the DPPH assay: BUC, DTE, DTT, GSH. In conclusion, it was demonstrated that dithiols may be more effective than monothiols in affording biomacromolecule protection from oxidative degradation.     

Model predictive control-based robust stabilization of a chemical reactor

The paper addresses an approach to robust stabilization of chemical continuous stirred tank reactors. State feedback was used for the stabilization and the feedback controller was designed using the robust model-based predictive control algorithm in which the symmetric constraints on input and output variables are taken into account. The known strategy was modified by adding integral action to the controller. Parameters of robust feedback controllers with and without integral action were found as solutions of a constrained optimization problem solved on the infinite prediction horizon. The possibility to stabilize chemical reactors with uncertainty using the robust model-based predictive control has been verified by simulations and compared with the optimal linear quadratic control and the model-based predictive control. The obtained results confirm that the robust model-based predictive control provides better results than other approaches.     

Polyamide grafted with polypyrrole: formation, properties, and stability

Conducting textiles of polyamide (PA) fabrics and polypyrrole (PPy) were prepared by in situ oxidative chemical polymerisation of pyrrole (Py) on the surface of PA textiles using FeCl₃ as oxidant. The anionic surfactant, dodecylbenzenesulphonic acid, was used as co-dopant during Py polymerisation on the textile surface. The influence of the monomer amount and polymerisation conditions on formation of the conducting PPy layer, conductivity, morphology, and stability of the prepared PA/PPy was studied. The conductivity of modified textiles decreased rapidly after the washing process, so a special Py-functionalised silane (1-(3-(triethoxysilyl)propylamino)-3-(1-H-pyrrole-1-yl)propan-2-ol; SP) was synthesised and applied to the PA surface prior to PPy formation. The presence of SP on the PA surface after completion of the sol-gel process was verified by Fourier transform infrared spectroscopy with an attenuated total reflectance. Pyrrole polymerisation was subsequently applied to the SP pre-treated textile surface. The influence of SP concentration on both the fastness of the conducting layer after the washing process and stability of the electrical conductivity of the prepared PA/PPy samples was investigated. Surface conductivity of the samples treated and untreated by the sol-gel process of SP was measured both prior to and after washing of the prepared textiles. It was found that an application of 0.6 mass % of SP significantly improved the fastness of the PPy layers. Examination of the modified PA surface using scanning electron microscopy disclosed the differences in the formation of PPy on PA textiles when using SP and also showed differences on the PPy modified textile surface prior to and after washing. The method of X-ray photoelectron spectroscopy was used for a detailed study of the surface composition. It was confirmed that the pre-treatment with Py-functionalised triethoxysilane significantly influenced the chemical composition of the PA surface modified with PPy.     

Preparation,identification and thermal properties of (CH3CH2COO)2Zn·2L·H2O (L=thiourea,nicotinamide, caffeine or theorbromine)

Zinc carboxylates complexed with N-donor ligands have potential antifungal effects. The preparation, identification and especially the thermal properties of four hitherto non-characterized compounds of this group of general formula (CH₃CH₂COO)₂Zn·2L·H₂O are described in this paper. The experimental results are confronted with present knowledge on analogous compounds.

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Zusammenfassung Komplexe aus Zinkkarboxylaten mit N-Donorliganden besitzen potentielle fungizide Effekte. Vorliegend werden Herstellung, Identifizierung und insbesondere die thermischen Eigenschaften von vier bislang nicht beschriebenen Verbindungen dieser Gruppe der allgemeinen Formel (CH₃CH₂COO)₂Zn·2L·H₂O beschrieben. Den experimentellen Ergebnissen werden die vorhandenen Kenntnisse über analoge Verbindungen gegenübergestellt.

     

Stability in coalition formation games

In the context of coalition formation games a player evaluates a partition on the basis of the set she belongs to. For this evaluation to be possible, players are supposed to have preferences over sets to which they could belong. In this paper, we suggest two extensions of preferences over individuals to preferences over sets. For the first one, derived from the most preferred member of a set, it is shown that a strict core partition always exists if the original preferences are strict and a simple algorithm for the computation of one strict core partition is derived. This algorithm turns out to be strategy proof. The second extension, based on the least preferred member of a set, produces solutions very similar to those for the stable roommates problem. Received August 1998/Final version June 20, 2000     

Study of water in Ca-montmorillonite by thermal analysis and positron annihilation lifetime spectroscopy

Journal of Thermal Analysis and Calorimetry - The aim of this study is to characterize adsorbed liquid in montmorillonite structure for different levels of adsorption by both thermoanalytical and...