Biotransformations of imbricatolic acid by Aspergillus niger and Rhizopus nigricans cultures

Microbial transformation of imbricatolic acid (1) by Aspergillus niger afforded 1alpha-hydroxyimbricatolic acid (2), while transformation with Rhizopus nigricans yielded 15-hydroxy-8,17-epoxylabdan-19-oic acid (3). When the diterpene 1 was added to a Cunninghamella echinulata culture, the main products were the microbial metabolites mycophenolic acid (4) and its 3-hydroxy derivative 5. All the structures were elucidated by spectroscopic methods. The cytotoxicity of these compounds towards human lung fibroblasts and AGS cells was assessed. While 4 and 5 showed low cytotoxicity, with IC50 values > 1000 microM against AGS cells and fibroblasts, 1alpha-hydroxyimbricatolic acid (2) presented moderate toxicity towards these targets, with IC50 values of 307 and 631 microM, respectively. The structure of 2 is presented for the first time.     

A finite element thermally coupled flow formulation for phase‐change problems

A finite element, thermally coupled incompressible flow formulation considering phase‐change effects is presented. This formulation accounts for natural convection, temperature‐dependent material properties and isothermal and non‐isothermal phase‐change models. In this context, the full Navier–Stokes equations are solved using a generalized streamline operator (GSO) technique. The highly non‐linear phase‐change effects are treated with a temperature‐based algorithm, which provides stability and convergence of the numerical solution. The Boussinesq approximation is used in order to consider the temperature‐dependent density variation. Furthermore, the numerical solution of the coupled problem is approached with a staggered incremental‐iterative solution scheme, such that the convergence criteria are written in terms of the residual vectors. Finally, this formulation is used for the solutions of solidification and melting problems validating some numerical results with other existing solutions obtained with different methodologies. Copyright © 2000 John Wiley & Sons, Ltd.     

Results coming from homogeneous and supported metallocene catalysts in the homo- and copolymerization of olefins

Ethylene, propylene and α-olefins were homo- and copolymerized in the presence of a series of homogeneous catalytic systems consisting of methylaluminoxane (MAO) and group IV metallocenes such as Et(Ind)₂ZrCl₂ (I), Me₂Si(Ind)₂ZrCl₂ (II), Et(2-Me-Ind)₂ZrCl₂ (III), Ph₂C(Flu)(Cp)ZrCl₂ (IV). It was found that the catalytic activity, the incorporation of comonomer in the case of copolymers, and the microstructure of the polymers depend on the catalyst's structure. For heterogeneous catalysts, several supports based on metal oxide compounds have been investigated, with special emphasis in those obtained by the sol-gel preparation technique. The homo- and copolymerization of the monomers in the homogeneous systems studied where also investigated using the same catalyst system, but in a heterogeneous medium. Comparative results from the homogeneous and heterogeneous systems are presented and discussed.     

Synthesis and characterization of the new ambidentate O‐cholesteryl‐O‐phenyl phosphorothioate ligand and its organoarsenic derivatives of phenoxarsin‐10‐yl and phenothiarsin‐10‐yl phosphorothioate

A new anionic phosphorothioate ligand that incorporates the bioactive cholesteryl group was obtained ( 2 ), Na(RR′P(S)O; R, O‐phenyl; R′, O‐cholesteryl) from the phenylphosphoramidate ( 1 ) and NaH in dioxane. In order to test the coordination ability of 2, two organoarsenic derivatives were prepared, O(C₆H₄)₂AsS(O)PRR′ ( 3 ) and S(C₆H₄)₂AsS(O)PRR′ ( 4 ) by reacting 2 with 10‐chlorophenoxarsine or 10‐chlorophenothiarsine. Compounds 2, 3 , and 4 were characterized by elemental microanalysis, IR, multi‐element NMR (¹H, ¹³C, and ³¹P), and mass spectrometry. The spectroscopic data suggest that the ligand is bonded to the arsenic only through the sulfur donor atom in both organoarsenic derivatives. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:6–10, 2000     

Raman spectroscopic characterization of cinnabarin produced by the fungus Pycnoporus sanguineus (Fr.) Murr.

Raman spectroscopy with 1064 nm laser excitation is used here to identify the chemical composition of the extracts obtained from Pycnoporus sanguineus fungus, in comparison with the data produced from the red fungus itself. Polar and non‐polar solvents were used to separate cinnabarin and ergosterol, respectively, the main components of each extract. The Raman spectra of the extracts are dominated by specific vibrational modes that can be related to these components; in the case of ergosterol the main bands are those assignable to CH stretching and deformation along with bands related to the aryl skeletal rings. The cinnabarin fraction, on the other hand, gives a Raman spectrum where the most important bands are those related to NH₂ bending (1510 cm⁻¹) and C quinonoid stretching (1647 cm⁻¹) modes. The Raman spectrum obtained directly from the fungus shows similarity with the cinnabarin fraction, in agreement with the literature information from extracts that cinnabarin is the most significant component present in the red fungus. This result highlights the potential of Raman spectroscopic techniques for the monitoring of the fungus extraction process undertaken in small industries. Copyright © 2007 John Wiley & Sons, Ltd.     

The Impact of Dextran Sodium Sulfate-Induced Gastrointestinal Injury on the Pharmacokinetic Parameters of Donepezil and Its Active Metabolite 6-O-desmethyldonepezil,and Gastric Myoelectric Activity in Experimental Pigs

Gastrointestinal side effects of donepezil, including dyspepsia, nausea, vomiting or diarrhea, occur in 20–30% of patients. The pathogenesis of these dysmotility associated disorders has not been fully clarified yet. Pharmacokinetic parameters of donepezil and its active metabolite 6-O-desmethyldonepezil were investigated in experimental pigs with and without small intestinal injury induced by dextran sodium sulfate (DSS). Morphological features of this injury were evaluated by a video capsule endoscopy. The effect of a single and repeated doses of donepezil on gastric myoelectric activity was assessed. Both DSS-induced small intestinal injury and prolonged small intestinal transit time caused higher plasma concentrations of donepezil in experimental pigs. This has an important implication for clinical practice in humans, with a need to reduce doses of the drug if an underlying gastrointestinal disease is present. Donepezil had an undesirable impact on porcine myoelectric activity. This effect was further aggravated by DSS-induced small intestinal injury. These findings can explain donepezil-associated dyspepsia in humans.     

Association of 4-n-Alkylbenzene Sulfonates with Hydrophobically Modified Poly (Diallyldimethylammonium) Chlorides

The association of poly (diallyldimethylammonium) chloride (PDDAC) hydrophobically modified with octyl, decyl, and dodecyl chlorides, with 4-n-alkylbenzene sulfonates, was studied in aqueous solution by ultrafiltration. Experimental data agree well with the Hill's equation for the association process. The association degree increases with the size of the sulfonate anion and decreases as the polyelectrolyte side chains length increases. This kind of polyelectrolyte is able to form hydrophobic microdomains lowering the availability of association sites due to a hypercoiling process. The association process was, in all cases, cooperative, having a maximum with the octyl derivative. The association degrees were significantly higher than those found with PDDAC itself. The standard free-energy contribution to the association process was between ?19 and ?20 kJ/mol of benzene sulfonate. These values are comparable with those recently found for a family of hydrophobic cationic polyelectrolytes at the water/chloroform interface. Therefore, in terms of the association process, it does not matter if the polyelectrolyte is adsorbed at a liquid/liquid interface or if it is soluble in a pure phase. The contribution of the methylene groups was very small, ranging from ?0.20 to ?0.50 kJ/mol. This reveals that the main interaction governing the association is the aromatic ring–ammonium group interaction.     

Obtaining of Ni<Subscript>0.65</Subscript>Zn<Subscript>0.35</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles at low temperature starting from metallic nitrates and polyols

This article presents a study on obtaining Ni, Zn ferrite starting from Fe(III), Ni (II), Zn (II) nitrates and some polyols: 1,2-propane diol, 1,3-propane diol and glycerol. While heating, a redox reaction takes place between nitrate anion and polyol, with formation of carboxylate type precursors. The obtained precursors have been investigated by thermal analysis, FT-IR spectrometry and atomic absorption spectroscopy. The thermal decomposition of the synthesized precursors up to 350 °C leads to the formation of Ni, Zn ferrite as unique phase, evidenced by XRD. The average diameter of the ferrite crystallites, estimated from XRD data, takes values within the range 20–50 nm, depending on the annealing temperature. Transmission Electron Microscopy has evidenced the obtaining of spherical, agglomerated nanoparticles. The magnetic properties of the synthesized samples, measured in cvasistatic magnetic field (50 Hz) are characteristic for the Ni, Zn ferrite nanoparticles, with narrow hysteresis cycle and values of the saturation magnetization <70 emu/g.