Biological Activity of Flavonoids Copper Complexes

Three flavonoid copper(II) complexes Cu₂(quercetin)(CH₃COO)₃(CH₃OH) ( 1 ), Cu(anthrarufin)(CH₃COO)·1/2H₂O ( 2 ) and Cu(naringin)(OCH₃)(CH₃OH)₂ ( 3 ) have been synthesized and characterized by elemental analysis, IR, electronic absorption and EPR (X‐band) spectroscopy. The complexes have a strong protective action over the Δsod1 mutant of S. cerevisiae against reactive oxygen radicals generated by an external source of free radicals (H₂O₂ or the superoxide‐generating, menadione). On the other hand, the complexes cleave DNA efficiently even in the absence of reducing agents. The main reactive oxygen species responsible for the DNA strand cleavage have been determined using radical scavengers. A probably mechanism of the DNA damage is proposed.     

A Screening Method for Polycyclic Aromatic Hydrocarbons Determination in Water by Headspace SPME with GC-FID

A simple method for determination of polycyclic aromatic hydrocarbons (PAHs) in water using headspace solid-phase microextraction (HS-SPME) with gas chromatography-flame ionisation detector (GC-FID) was developed. In order to obtain the convenient experimental conditions for HS-SPME extraction an experimental design with two steps was accomplished. A 2^6-2 fractional factorial design and central composite design (CCD) considering three significant factors were used. Naphthalene, anthracene and fluoranthene were chosen as representatives of two, three and four aromatic rings, and the global response of three PAHs was used for the results, evaluation. The chosen extraction conditions were: 85 μm polyacrylate fibre; 50 °C temperature; 60 min time; 20 mL-dissolution volume (in 40 mL glass vial); without salt addition; and 2 min desorption time. The procedure was extended to other seven PAHs (acenaphthylene, acenaphthene, fluorene, phenanthrene, pyrene, chrysene and benzo(a)anthracene) and the analytical characteristics were checked. The limit of detection (LOD) was from 0.08 (anthracene) to 0.20 μg L^?1 (naphthalene). The precision expressed as relative standard deviation (RSD in %) using 50 μg L^?1 of each analyte ranged from 6.8 to 17 %. The method was applied to the analysis of the surface waters and leaching waters of contaminated soils from Gipuzkoa (North Spain). The PAHs were not detected in surface water samples. Most of the PAHs were found in the leachates from contaminated soils showing a maximum global value of 75.5 μg L^?1.     

Room-temperature synthesis and conductivity of the pyrochlore type Dy2(Ti1−yZry)2O7 (0?y?1) solid solution

Different compositions in a solid solution of general formula Dy₂(Ti_1−yZr_y)₂O₇, showing high oxygen ion conductivity, have been successfully prepared at room temperature via mechanochemical synthesis. Stoichiometric mixtures of the constituent oxides were dry milled together in a planetary ball mill by using zirconia vials and balls. Chemical changes in the powder mixtures as a function of composition and milling time were followed by X-ray diffraction and revealed that, in all cases and after milling for 19 h, the powder mixtures consisted of a single phase. Electrical properties were measured on sintered pellets as a function of frequency, temperature and zirconium content, revealing an increase in conductivity of more than one order of magnitude for y?0.4, which, as observed in the similar Y₂(Ti_1−yZr_y)₂O₇, has been related with the onset of disordering of the anion sublattice. Despite increasing structural disorder with increasing Zr content, conductivity remains almost constant for y>0.6, reaching a maximum value of ∼5×10⁻³ for Dy₂Zr₂O₇ at 900 °C.     

Synthesis of Novel <Emphasis Type="Italic">D</Emphasis>-<Emphasis Type="Italic">Seco</Emphasis>-Pregnenes

Summary. A new synthetic route was developed for the preparation of trans-3-hydroxy-16,17-seco-pregna-5,17(20)-dien-16-al, using Grob fragmentation as the key step. This seco-steroid contains a formyl group and an unsaturated side-chain in a sterically favourable position, and is therefore a promising starting material for the synthesis of novel condensed steroid heterocycles.Received March 22, 2003; accepted April 22, 2003 Published online September 25, 2003     

Micelle-sequestered dissociation of cationic DNA-intercalated drugs: unexpected surfactant-induced rate enhancement

Detergent sequestration using micelles as a hydrophobic sink for dissociated drug molecules is an established technique for determination of dissociation rates. The anionic surfactant molecules are generally assumed not to interact with the anionic DNA and thereby not to affect the rate of dissociation. By contrast, we here demonstrate that the surfactant molecules sodium dodecyl sulfate (SDS), sodium decyl sulfate, and sodium octyl sulfate all induce substantial rate enhancements of the dissociation of intercalators from DNA. Four different cationic DNA intercalators are studied with respect to surfactant-induced dissociation. Except for the smallest intercalator, ethidium, the dissociation rate constants increase monotonically with surfactant concentration both below cmc and (more strongly) above cmc, much more than expected from electrostatic effects of increased counterion concentration. The rate enhancement, most pronounced for the bulky, multicationic, hydrophobic DNA ligands in this study, indicates a reduction of the activation energy for the ligand to pass out from a deeply penetrating intercalation site of DNA. The discovery that surfactants enhance the rate of dissociation of cationic DNA-intercalators implies that rate constants previously determined by micelle-sequestered dissociation may have been overestimated. As an alternative, more reliable method, we suggest instead the addition of excess of dummy DNA as an absorbent for dissociated ligand.     

The modulating possibilities of dicarbollide clusters: optimizing the Kharasch catalysts

exo-Cluster dicarbollides substitution has allowed tuning of the E degrees (Ru(II)/Ru(III)) potential to obtain the best-performing Kharasch catalyst. We postulate that this is possible through the to-and-fro electron movement between the boron cluster and the sulfonium moieties.     

Synthesis of 2-(imidazolylamino)benzothiazoles

Treatment of derivatives of 5-phenylthioureido-3H-imidazole-4-carboxylic acid with bromine afforded 2-(imidazolylamino)benzothiazoles.     

On the High Viscosity of Aqueous Solution of Lysozyme Induced by Some Organic Solvents

A remarkably high viscosity has been induced in protein aqueous solutions by the addition of certain structurally related organic solvents. The effect has been observed for lysozyme aqueous solutions containing tetramethylurea (TMU), dimethylsulfoxide (DMSO), dimethylformamide, and hexamethylphosphortriamide. The effect has also been induced in ferrocytochrome c aqueous solutions by TMU. Critical concentrations for both the protein and organic solvent were verified for the onset of the viscosity increase. A common feature of the solvents which were able to induce the effect is a dipolar moiety (C=O, S → O and P → O) and a nonpolar region represented by the methyl groups. The resulting fluids show an extremely restricted flow and a typical non-Newtonian, pseudoplastic behavior. Use was made of¹H nuclear magnetic resonance (NMR) and Raman spectroscopy to characterize protein structural modifications and of¹³C NMR to investigate changes in relaxation times and chemical shifts in the solvent/water solutions. A systematic rheological characterization of the systems was undertaken for some of the solvents, and unusual patterns of viscous effects were identified for the solvent/water systems both with and without protein. The process was found to be at least partially reversible, as concluded from the recovered original solution rheological characteristics and the original protein¹H NMR spectrum, after eliminating the organic solvent by ultrafiltration. The whole process was characterized as consisting of two mutually independent stages. The first involves an extensive conformational transition of the polypeptide backbone, from a predominantly α-helical to increased random coiled and β-sheet structures, with the occurrence of nonorthodox protein secondary structures at regions above the solvent critical point. The second stage consists of short-lived interchain contacts leading to an entanglement of the macromolecular system as a whole. A microphase reversion in the organic solvent/water mixture, supported by¹³C NMR and rheological results, is proposed as the driving force causing the observed behavior.     

Thermal behaviour of xanthinium salts of Zn(II), Cd(II) and Hg(II)

Salts [XanH⁺]₂[MCl ₄ ^2- ] (where XanH⁺=protonated form of xanthine and M=Zn(II), Cd(II) and Hg(II) have been synthesized and studied by IR,¹H-NMR, TG and DSC. The metal is not coordinated to the ligand and forms a salt-like structure. The cationic proton is on N(7). Thermal decomposition of these salts occurs in two steps: (i) dehalogenation and (ii) decomposition. Dehalogenation enthalpies have been calculated from DSC curves.

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Zusammenfassung (XanH⁺)₂(MCl ₄ ^2- )-Salze (worin XanH⁺ die protonisierte Form von Xanthin bedeutet und M=Zn(II), Cd(II) oder Hg(II) ist) wurden synthetisiert und mit IR,¹H-NMR, TG und DSC untersucht. In diesem Fall liegt keine Koordination des Metalls mit dem Liganden vor, und es bildet sich eine salzartige Struktur aus. Das kationische Proton ist an N(7) lokalisiert. Die thermische Zersetzung dieser Salze erfolgt in zwei Schritten: (i) Dehalogenisierung und (ii) Zersetzung. Dehalogenierungsenthalpien wurden aus DSC-Kurven berechnet.

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- -, [XanH⁺]₂[MCl ₄ ^2– ], XanH⁺ — , M — , . , . . : . - .

     

Anomalous behaviour of the Landé factors and the chemical shift close to the dissociation limit of the B state of molecular iodine

Resonances in a modulated light beam have been observed on five transitions in the visible band system of I₂. Landé factors g_J and chemical shifts g₁ have been measured for levels very close to the dissociation limit of the B state.