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Pure Compounds (pure + compound)
Selected AbstractsIn vitro studies on antioxidant activity of lignans isolated from sesame cake extractJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 10 2005Kizhiyedathu Polachira Suja Abstract The antioxidant activity of compounds isolated from a methanolic extract of commercial sesame cake was studied using a peroxidation model and a radical-scavenging method. Pure compounds were isolated from the extract by preparative high-performance liquid chromatography (HPLC) and identified and confirmed as sesamol, sesamin, sesamolin, sesaminol diglucoside and sesaminol triglucoside by HPLC, infrared, nuclear magnetic resonance and mass spectrometry. When the rate of inhibition of lipid peroxidation and the superoxide radical-scavenging power of the individual compounds were evaluated, the compounds showed antioxidant activity to different extents. The antioxidant activity of compounds by the ,-carotene-bleaching assay followed the order sesamol > sesamolin , sesamin > butylated hydroxytoluene (BHT) > sesaminol triglucoside > sesaminol diglucoside. By the thiocyanate method the inhibition of linoleic acid peroxidation shown by sesamol, sesamin, sesamolin, sesaminol triglucoside, sesaminol diglucoside and BHT at 200 mg l,1 was 77, 60, 69, 32, 25 and 49% respectively. A concentration,dependent superoxide,scavenging effect was also shown by these compounds. Sesamolin had an appreciable effect at 300 and 500 mg l,1, while the other compounds were more effective at 100 mg l,1. The study also established the occurrence of sesamol in the methanolic extract of defatted sesame cake for the first time. Copyright © 2005 Society of Chemical Industry [source] Intra- and interlaboratory calibration of the DR CALUX® bioassay for the analysis of dioxins and dioxin-like chemicals in sedimentsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2004Harrie T. Besselink Abstract In the Fourth National Policy Document on Water Management in the Netherlands [1], it is defined that in 2003, in addition to the assessment of chemical substances, special guidelines for the assessment of dredged material should be recorded. The assessment of dredged material is based on integrated chemical and biological effect measurements. Among others, the DR CALUX® (dioxin responsive,chemically activated luciferase expression) bioassay has tentatively been recommended for inclusion in the dredged material assessment. To ensure the reliability of this bioassay, an intra- and interlaboratory validation study, or ring test, was performed, organized by the Dutch National Institute for Coastal and Marine Management (RIKZ) in cooperation with BioDetection Systems BV (BDS). The intralaboratory repeatability and reproducibility and the limit of detection (LOD) and quantification (LOQ) of the DR CALUX bioassay were determined by analyzing sediment extracts and dimethyl sulfoxide (DMSO) blanks. The highest observed repeatability was found to be 24.1%, whereas the highest observed reproducibility was calculated to be 19.9%. Based on the obtained results, the LOD and LOQ to be applied for the bioassay are 0.3 and 1.0 pM, respectively. The interlaboratory calibration study was divided into three phases, starting with analyzing pure chemicals. During the second phase, sediment extracts were analyzed, whereas in the third phase, whole sediments had to be extracted, cleaned, and analyzed. The average interlaboratory repeatability increased from 14.6% for the analysis of pure compound to 26.1% for the analysis of whole matrix. A similar increase in reproducibility with increasing complexity of handlings was observed with the interlaboratory reproducibility of 6.5% for pure compound and 27.9% for whole matrix. The results of this study are intended as a starting point for implementing the integrated chemical,biological assessment strategy and for systematic monitoring of dredged materials and related materials in the coming years. [source] Facile and Reproducible Synthesis of Nanostructured Colloidal ZnO Nanoparticles from Zinc Acetylacetonate: Effect of Experimental Parameters and Mechanistic InvestigationsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2009Alessia Famengo Abstract A facile and reproducible route to nanostructured colloidal ZnO nanoparticles was developed by controlled hydrolysis and condensation of zinc acetylacetonate in alkaline conditions. By reaction of an ethanolic solution of Zn(acac)2 with NaOH in a 1:2 molar ratio, after reflux, ZnO spherical nanoparticles were obtained that displayed a homogeneous size distribution; particle diameters ranged from 6 to 10 nm, as evidenced by transmission electron microscopy (TEM) analysis. The same reaction was carried out also in water, glycerol and 1,2-propanediol, to investigate the effect of the solvent viscosity and dielectric constant on the final features of the obtained material. Irrespective of the nature of the solvent, X-ray diffraction (XRD) analysis shows the formation ofhexagonal ZnO, whereas the presence of residual unreacted Zn(acac)2 could be ruled out. Indeed, different particle sizes and very different morphologies were obtained. Also the reflux step was shown to be a key factor in avoiding the fast precipitation of a floc and achieving a pure compound, which was isolated and thoroughly characterised. The composition of the obtained ZnO was determined by elemental analysis, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), showing the formation of pure ZnO. IR spectroscopy evidenced the presence of adsorbed organic ligands on the colloid surfaces. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) revealed the presence of medium- to high-strength acidic sites on the ZnO surface. To gain a deeper insight into the formation mechanisms of these nanostructures, time-resolved UV/Vis and XAS studies were performed on the ethanol solution used for the synthesis of the oxide and also on the solid specimen, obtained after the refluxing step. No remarkable changes could be evidenced in the solution after the addition of an understoichiometric amount of NaOH, but the growth of the ZnO nanoparticles could be followed by UV/Vis spectra. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Dispersion polymerization of vinyl monomers in supercritical carbon dioxide in the presence of drug molecules: A one-pot route for the preparation of controlled delivery systemsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2008Alessandro Galia Abstract The polymerization of 1-vinyl-2-pyrrolidone in supercritical carbon dioxide in the presence of ibuprofen as a model drug was investigated as a new one-pot process for the preparation of polymer-based drug delivery systems (DDSs). The composites were prepared at 65 °C and P = 31,42 MPa by changing the initial concentration of the drug and the concentration of a crosslinking agent and that of a hydrophobic comonomer. The effects of these parameters on the performances of the polymerization and on the in vitro release kinetics of ibuprofen were studied. In all the experiments, part of the drug was entrapped inside the polymer particles and dissolved more slowly with respect to the pure compound. Copolymerization with methyl methacrylate was the most effective route to obtain a DDS with sustained temporal release of the drug molecule. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7429,7446, 2008 [source] Partition Coefficient Kow of Benzene, Ethanol and Aniline in Benzene-ethanol and Aniline-benzene Mixtures and Coefficient of Distribution Kmix of these MixturesMOLECULAR INFORMATICS, Issue 4 2006M. Rucki Abstract The study related to partition coefficients between n-octanol and water Kow of compounds in binary mixtures benzene-ethanol and benzene-aniline was carried out. Partition coefficients of benzene, aniline and ethanol for different values of molar ratio of benzene and different total concentration of compounds in the mixtures benzene-ethanol and benzene-aniline were determined. Coefficient of distribution Kmix was determined for both mixtures. In benzene-ethanol mixture collected results show statistically significant deviations the Kow of benzene from values for pure compound. For ethanol, there are no statistically significant deviations from values for pure compound. But also there are some trends of changes of Kow. In benzene-aniline mixture collected results show statistically significant deviations of the Kow of benzene and aniline from values for pure compounds. Changes of Kow were used for explanation of acute toxicity of binary mixtures benzene-ethanol and aniline-benzene. [source] Rapid screening of clenbuterol in urine samples by desorption electrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2008Ziqing Lin Rapid screening of clenbuterol in urine was performed by combining desorption electrospray ionization (DESI) and tandem mass spectrometry (MS/MS). Optimization experiments were carried out including the selection of substrates, spray solutions, nebulizing gas pressures, high-voltage power supplies and flow rates of spray solution. The limit of detection (LOD), defined as the lowest quantity that can be detected, was 5.0 pg for the pure compound. Using DESI coupled with solid-phase extraction (SPE), the linear response range was from 10 to 400,ng/mL (R2,=,0.993) and the concentration LOD for urine sample was 2.0,ng/mL. The analysis for one spiked urine sample was achieved within 4,min. In addition to the fast analysis speed, MS/MS provided structural information for the confirmation of clenbuterol. Urine samples from different people were investigated and the recoveries were within 100,±,20%. The developed method can potentially be used for screening of clenbuterol in doping control. Copyright © 2008 John Wiley & Sons, Ltd. [source] Synthesis, Structure, and Physico-optical Properties of Manganate(II)-Based Ionic LiquidsCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2010Slawomir Pitula Dr. Abstract Several ionic liquids (ILs) based on complex manganate(II) anions with chloro, bromo, and bis(trifluoromethanesulfonyl)amido (Tf2N) ligands have been synthesized. As counterions, n- alkyl-methylimidazolium (Cnmim) cations of different chain length (alkyl=ethyl (C2), propyl (C3), butyl (C4), hexyl (C6)) were chosen. Except for the 1-hexyl-3-methylimidazolium ILs, all of the prepared compounds could be obtained in a crystalline state at room temperature. However, each of the compounds displayed a strong tendency to form a supercooled liquid. Generally, solidification via a glass transition took place below ,40,°C. Consequently, all of these compounds can be regarded as ionic liquids. Depending on the local coordination environment of Mn2+, green (tetrahedrally coordinated Mn2+) or red (octahedrally coordinated Mn2+) luminescence emission from the 4T(G) level is observed.1 The local coordination of the luminescent Mn2+ centre has been unequivocally established by UV/Vis as well as Raman and IR vibrational spectroscopies. Emission decay times measured at room temperature in the solid state (crystalline or powder) were generally a few ms, although, depending on the ligand, values of up to 25,ms were obtained. For the bromo compounds, the luminescence decay times proved to be almost independent of the physical state and the temperature. However, for the chloro- and bis(trifluoromethanesulfonyl)amido ILs, the emission decay times were found to be dependent on the temperature even in the solid state, indicating that the measured values are strongly influenced by nuclear motion and the vibration of the atoms. In the liquid state, the luminescence of tetrahedrally coordinated Mn2+ could only be observed when the tetrachloromanganate ILs were diluted with the respective halide ILs. However, for [C3mim][Mn(Tf2N)3], in which Mn2+ is in an octahedral coordination environment, a weak red emission from the pure compound was found even in the liquid state at elevated temperatures. [source] Mutagenicity of nitroaromatic degradation compoundsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2003Ranjit S. Padda Abstract The mutagenicity of 2,4-dinitrotoluene (24DNT), and 2,6-dinitrotoluene (26DNT), and their related transformation products such as hydroxylamine and amine derivatives, which are formed by Clostridium acetobutylicum, were tested in crude cell extracts using Salmonella typhimurium TA100. A previous publication already reported the mutagenic activities of 2,4,6-trinitrotoluene (TNT) and its related hydroxylamine derivatives in this test system. A time course of the mutagenicity during the anaerobic transformation of TNT, 24DNT, and 26DNT was also investigated under the same conditions to compare with the results from the pure compounds. The monohydroxylamino intermediates 2-hydroxylamino-4-nitrotoluene (2HA4NT), 4-hydroxylamino-2-nitrotoluene (4HA2NT) and 2-hydroxylamino-6-nitrotoluene (2HA6NT) formed during anaerobic transformation of dinitrotoluenes were proven to be mutagenic in the Ames test using Salmonella typhimurium TA100. This study reports that 4HA2NT is the most stable derivative, whereas 2HA4NT and 2HA6NT are less stable and these intermediates are mutagenic in the Ames test. Both 24DNT and 26DNT and their final metabolites 2,4-diaminotoluene (24DAT) and 2,6-aminotoluene (26DAT) appeared nonmutagenic. In a time-course study of TNT degradation, the temporal sample containing 85% of 2,4-dihydroxylamino-6-nitrotoluene (24HA6NT) is most mutagenic. These observations suggest that the bioremediation approach for treatment of 24DNT and 26DNT should be carried past the hydroxylamino intermediate. [source] Antioxidant properties of extracts and compounds from Psoralea morisianaEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 7-8 2005Antonella Rosa Abstract The antioxidant activity of various extracts (MeOH, petroleum ether, EtOAc) from the aerial parts of Psoralea morisiana, an endemic Sardinian plant, was evaluated during autoxidation and iron-mediated oxidation of linoleic acid at 37,°C and during cholesterol oxidation at 140,°C, in the absence of solvent. The activity of erybraedin,C, bitucarpin,A and plicatin,B, isolated from the extracts, was investigated under the same experimental conditions and compared to that of BHT and ,-tocopherol. All the extracts, erybraedin,C (major constituent of the extracts) and plicatin,B showed powerful antioxidant properties. None of the extracts and pure compounds showed any prooxidant activity. The cytotoxicity of the extracts, erybraedin,C, and plicatin,B was further evaluated in VERO cells, a line of fibroblasts derived from monkey kidney. Erybraedin,C, at non-cytotoxic concentrations, showed a strong inhibition of FeCl3 -induced oxidation in VERO cells. [source] Stereoselective Synthesis of myo -, neo -, L - chiro, D - chiro, allo -, scyllo -, and epi -Inositol Systems via Conduritols Prepared from p -BenzoquinoneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2003Michael Podeschwa Abstract A practical route is described for the flexible preparation of a wide variety of inositol stereoisomers and their polyphosphates. The potential of this approach is demonstrated by the synthesis of myo -, L - chiro -, D - chiro -, epi -, scyllo -, allo -, and neo -inositol systems. Optically pure compounds in either enantiomeric form can be prepared from p -benzoquinone via enzymatic resolution of a derived conduritol B key intermediate. High-performance anion-exchange chromatography with pulsed amperometric detection permits inositol stereoisomers to be resolved and detected with high sensitivity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Fingerprinting Analysis of Rhizoma Chuanxiong of Commercial Types using 1H Nuclear Magnetic Resonance Spectroscopy and High Performance Liquid Chromatography MethodJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2009Hai-Lin Qin Abstract The 1H nuclear magnetic resonance (1H NMR) fingerprints of fractionated non-polar extracts (control substance for a plant drug (CSPD) A) from Rhizoma chuanxiong, the rhizomes of Ligusticum chuanxiong Hort., of seven specimens from different sources were measured on Fourier Transform (FT)-NMR spectrometer and assigned by comparing them with the 1H NMR spectra of the isolated pure compounds. The 1H NMR fingerprints showed exclusively characteristic resonance signals of the major special constituents of the plant. Although the differences in the relative intensity of the 1H NMR signals due to a discrepancy in the ratio of the major constituents among these samples could be confirmed by high performance liquid chromatography analysis, the general features of the 1H NMR fingerprint established for an authentic sample of the rhizomes of L. chuanxiong exhibited exclusive data from those special compounds and can be used for authenticating L. Chuanxiong species. [source] Synthesis of new deuterium-labelled lignanolactonesJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 13 2008Eija Leppälä Abstract Deuteration of several lignanolactones, using 2H3PO4·BF3/2H2O as the deuteration reagent, is described, affording new stable isotopically pure polydeuterated lignans. All aromatic hydrogens are exchanged, including the less active ones. The order of 1H/2H exchange is studied by comparing calculated electrostatic potential values and experimental observations. Labile deuteriums are exchanged back to hydrogens with methanolic HCl to achieve stable isotopically pure compounds. Copyright © 2008 John Wiley & Sons, Ltd. [source] Prediction of global VLE for mixtures with improved renormalization group theoryAICHE JOURNAL, Issue 1 2006Jianguo Mi Abstract The recently proposed renormalization group (RG) theory is reformulated within the context of density functional theory and applied to predicting global vapor,liquid equilibria (VLE) of Lennard,Jones chain pure fluids and fluid mixtures. An accurate equation based on the solution of the first-order mean-sphere approximation (FMSA) is adopted outside the critical region. Inside the critical region, the direct correlation function of FMSA is incorporated into the new RG transformation to describe the long-range fluctuation, which is conformal to general inhomogeneous studies. The new RG theory is applied to correcting real mixture phase envelopes, as well as corresponding phase diagrams of pure compounds for the critical region. The calculated results are in substantial agreement with those from experiment and molecular simulation both inside and outside the critical region. The new method is highly predictive because no adjustable parameters and no mixing rule are needed for both model and real fluid mixtures. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Antinociceptive properties of coumarins, steroid and dihydrostyryl-2-pyrones from Polygala sabulosa (Polygalaceae) in miceJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 1 2006Juliana V. Ardenghi We have investigated the possible antinociceptive action of the extract, fractions and pure compounds obtained from the whole plant Polygala sabulosa A. W. Bennett (Polygalaceae) in acetic acid-induced visceral pain in mice. Intraperitoneal injection of animals with the hydroalcoholic extract and fractions (CH2Cl2, EtOAc, n -BuOH, aqueous fraction) (1,100 mg kg,1) caused a dose-related and significant inhibition of the acetic acid-induced visceral nociceptive response. The CH2Cl2, EtOAc and n -BuOH fractions were more potent than the hydroalcoholic extract and aqueous fraction. The isolated compounds dihydrostyryl-2-pyrones (1, 2, 3), styryl-2-pyrone (7), ,-spinasterol (9), scopoletin (10) and two esters of the coumarin (scopoletin) obtained semisynthetically, acetylscopoletin (10a) and benzoylscopoletin (10b) (0.001,10 mg kg,1), exhibited significant and dose-related antinociceptive effects against acetic acid-induced visceral pain. The results distinguished, for the first time, the extract, fractions and pure compounds obtained from P. sabulosa that produced marked antinociception against the acetic acid-induced visceral nociceptive response, supporting the ethnomedical use of P. sabulosa. [source] Purification of alkaloids from Corydalis yanhusuo W. T. Wang using preparative 2-D HPLCJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2009Jing Zhang Abstract Two-dimensional preparative multi-channel parallel high performance liquid chromatography was successfully applied for the first time to isolate and purify alkaloids from Corydalis yanhusuo. The experiments were performed in off-line mode using the same preparative chromatographic column with pH 3.5 in the first and pH 10.0 in the second separation dimension. In the preparative process, UV-triggered fraction collection was used in the first dimension while UV and MS-triggered collection were used in the second dimension for reasons of sensitivity and complementarity. Two pure compounds and nine fractions were obtained in the first dimension. Then two representative fractions were further purified in the second dimension and six pure compounds were obtained. The results demonstrated that this procedure is an effective approach for the preparative isolation and purification of alkaloids from Corydalis yanhusuo. Based on the different pH values of the mobile phase in this method, it is also suitable for the preparative isolation and purification of other compounds from TCMs which are sensitive to the pH of the solutions. Moreover, this method will be a promising tool for the purification of low content compounds from natural products. [source] Enantiomeric composition studies in Lavandula species using supercritical fluidsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2005Gema Flores Abstract Characteristic aroma compounds in plants and essential oils of Lavandula from different varieties were examined. The study of the qualitative and quantitative composition of the major volatile components was faced by developing a method based on the use of supercritical fluid extraction-GC-MS (SFE-GC-MS). The optimization of a variety of parameters affecting SFE extraction enabled RSDs from three replicates lower than 2% to be achieved. Equally, recoveries of up to 59% were obtained by applying the proposed method. The use of multidimensional GC was necessary to enantiomerically resolve the target compounds. The obtained results showed enantiomeric purities >90% for all studied compounds in all varieties considered, proving the natural invariability of the enantiomeric composition of the compounds of interest. This information can be useful in authenticity studies as well as in selecting natural sources of enantiomerically pure compounds. [source] Prediction of Flash Point Temperature of Pure Components Using a Quantitative Structure,Property Relationship ModelMOLECULAR INFORMATICS, Issue 6 2008Farhad Gharagheizi Abstract In this work, a general Quantitative Structure,Property Relationship (QSPR) model (, , and ) for the prediction of flash points of 1030 pure compounds is developed. Genetic Algorithm-based Multivariate Linear Regression (GA-MLR) technique is used to select four chemical structure-based molecular descriptors from a pool containing 1664 molecular descriptors. [source] Partition Coefficient Kow of Benzene, Ethanol and Aniline in Benzene-ethanol and Aniline-benzene Mixtures and Coefficient of Distribution Kmix of these MixturesMOLECULAR INFORMATICS, Issue 4 2006M. Rucki Abstract The study related to partition coefficients between n-octanol and water Kow of compounds in binary mixtures benzene-ethanol and benzene-aniline was carried out. Partition coefficients of benzene, aniline and ethanol for different values of molar ratio of benzene and different total concentration of compounds in the mixtures benzene-ethanol and benzene-aniline were determined. Coefficient of distribution Kmix was determined for both mixtures. In benzene-ethanol mixture collected results show statistically significant deviations the Kow of benzene from values for pure compound. For ethanol, there are no statistically significant deviations from values for pure compound. But also there are some trends of changes of Kow. In benzene-aniline mixture collected results show statistically significant deviations of the Kow of benzene and aniline from values for pure compounds. Changes of Kow were used for explanation of acute toxicity of binary mixtures benzene-ethanol and aniline-benzene. [source] Critical assessment of the applicability of gas chromatography-combustion-isotope ratio mass spectrometry to determine amino sugar dynamics in soilRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2009Charlotte Decock Amino sugars in soils have been used as markers of microbial necromass and to determine the relative contribution of bacterial and fungal residues to soil organic matter. However, little is known about the dynamics of amino sugars in soil. This is partly because of a lack of adequate techniques to determine ,turnover rates' of amino sugars in soil. We conducted an incubation experiment where 13C-labeled organic substrates of different quality were added to a sandy soil. The objectives were to evaluate the applicability of compound-specific stable isotope analysis via gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) for the determination of 13C amino sugars and to demonstrate amino sugar dynamics in soil. We found total analytical errors between 0.8 and 2.6, for the ,13C-values of the soil amino sugars as a result of the required ,13C-corrections for isotopic alterations due to derivatization, isotopic fractionation and analytical conditions. Furthermore, the ,13C-values of internal standards in samples determined via GC-C-IRMS deviated considerably from the ,13C-values of the pure compounds determined via elemental analyzer IRMS (with a variation of 9 to 10, between the first and third quartile among all samples). This questions the applicability of GC-C-IRMS for soil amino sugar analysis. Liquid chromatography-combustion-IRMS (LC-C-IRMS) might be a promising alternative since derivatization, one of the main sources of error when using GC-C-IRMS, is eliminated from the procedure. The high 13C-enrichment of the substrate allowed for the detection of very high 13C-labels in soil amino sugars after 1 week of incubation, while no significant differences in amino sugar concentrations over time and across treatments were observed. This suggests steady-state conditions upon substrate addition, i.e. amino sugar formation equalled amino sugar decomposition. Furthermore, higher quality substrates seemed to favor the production of fungal-derived amino sugars. Copyright © 2009 John Wiley & Sons, Ltd. [source] Scaling-up of complex whole-cell bioconversions in conventional and non-conventional mediaBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2010Marco P.C. Marques Abstract The use of whole cells is becoming a more common approach in pharmaceutical and agrochemical industries in order to obtain pure compounds with fewer production steps, higher yields, and cleaner processes, as compared to those achieved with traditional strategies. Whole cells are often used as enzymes pools, in particular when multi-step reactions and/or co-factor regeneration are envisaged. Nonetheless, published information on the scale-up of such systems both in aqueous and in two-phase aqueous,organic systems is relatively scarce. The present work aims to evaluate suitable scale-up criteria in conventional and non-conventional medium for a whole-cell bioconversion that uses resting cells of Mycobacterium sp. NRRL B-3805 to cleave the side chain of ,-sitosterol, a poorly water-soluble substrate. The experiments were performed in 24-well microtiter plates and in 250,mL shaken flasks as orbital stirred systems, and in 300,mL stirred tanks as mechanically stirred systems. Results show that productivity yields were similar in all scales tested, when maintaining oxygen mass transfer coefficients constant in aqueous systems, or when maintaining constant volumetric power consumption in aqueous,organic two-phase systems. Biotechnol. Bioeng. 2010;106: 619,626. © 2010 Wiley Periodicals, Inc. [source] Cytotoxic Polyketides Containing Tetramic Acid Moieties Isolated from the Fungus Myceliophthora Thermophila: Elucidation of the Relationship between Cytotoxicity and StereoconfigurationCHEMISTRY - A EUROPEAN JOURNAL, Issue 24 2007Yu-Liang Yang Dr. Abstract Five new polyketides that contain tetramic acids, myceliothermophins A,E, were isolated from the thermophilic fungus Myceliophthora thermophila. Two sets of 5-alkyl-5-hydroxyl (or 5-methoxyl)-1H -pyrrol-2(5H)-one diastereomers, myceliothermophins A/B and C/D, were separated as pure compounds by using silica-gel column chromatography and recycling reverse-phase high-performance liquid chromatography (RP-HPLC). The relative configurations of the chiral centers in 5-alkyl-5-hydroxyl (or 5-methoxyl)-1H -pyrrol-2(5H)-one moieties were deduced from NOESY correlations. In the cytotoxic assay, the 5-(2-methylpropyldiene)-1H -pyrrol-2(5H)-one analogue (myceliothermophin E) exhibited inhibition against four cancer cell lines. In addition, the significant inhibitory effect of myceliothermophins A and C and the inactivity of myceliothermophins B and D revealed the importance of the relative configurations of 5-alkyl-5-hydroxyl (or 5-methoxyl)-1H -pyrrol-2(5H)-one moieties on their cytotoxicity potency against cancer cells. [source] The World of , - and , -Peptides Comprised of Homologated Proteinogenic Amino Acids and Other ComponentsCHEMISTRY & BIODIVERSITY, Issue 8 2004Dieter Seebach The origins of our nearly ten-year research program of chemical and biological investigations into peptides based on homologated proteinogenic amino acids are described. The road from the biopolymer poly[ethyl (R)-3-hydroxybutanoate] to the , -peptides was primarily a step from organic synthesis methodology (the preparation of enantiomerically pure compounds (EPCs)) to supramolecular chemistry (higher-order structures maintained through non-covalent interactions). The performing of biochemical and biological tests on the , - and , -peptides, which differ from natural peptides/proteins by a single or two additional CH2 groups per amino acid, then led into bioorganic chemistry and medicinal chemistry. The individual chapters of this review article begin with descriptions of work on , -amino acids, , -peptides, and polymers (Nylon-3) that dates back to the 1960s, even to the times of Emil Fischer, but did not yield insights into structures or biological properties. The numerous, often highly physiologically active, or even toxic, natural products containing ,- and ,-amino acid moieties are then presented. Chapters on the preparation of homologated amino acids with proteinogenic side chains, their coupling to provide the corresponding peptides, both in solution (including thioligation) and on the solid phase, their isolation by preparative HPLC, and their characterization by mass spectrometry (HR-MS and MS sequencing) follow. After that, their structures, predominantly determined by NMR spectroscopy in methanolic solution, are described: helices, pleated sheets, and turns, together with stack-, crankshaft-, paddlewheel-, and staircase-like patterns. The presence of the additional CC bonds in the backbones of the new peptides did not give rise to a chaotic increase in their secondary structures as many protein specialists might have expected: while there are indeed more structure types than are observed in the , -peptide realm , three different helices (10/12 -, 12 -, and 14 -helix) if we include oligomers of trans -2-aminocyclopentanecarboxylic acid, for example , the structures are already observable with chains made up of only four components, and, having now undergone a learning process, we are able to construct them by design. The structures of the shorter , -peptides can also be reliably determined by molecular-dynamics calculations (in solution; GROMOS program package). Unlike in the case of the natural helices, these compounds' folding into secondary structures is not cooperative. In , - and , -peptides, it is possible to introduce heteroatom substituents (such as halogen or OH) onto the backbones or to incorporate heteroatoms (NH, O) directly into the chain, and, thanks to this, it has been possible to study effects unobservable in the world of the , -peptides. Tests with proteolytic enzymes of all types (from mammals, microorganisms, yeasts) and in vivo examination (mice, rats, insects, plants) showed , - and , -peptides to be completely stable towards proteolysis and, as demonstrated for two , -peptides, extraordinarily stable towards metabolism, even when bearing functionalized side chains (such as those of Thr, Tyr, Trp, Lys, or Arg). The , -peptides so far examined also normally display no or only very weak cytotoxic, antiproliferative, antimicrobial, hemolytic, immunogenic, or inflammatory properties either in cell cultures or in vivo. Even biological degradation by microbial colonies of the types found in sewage-treatment plants or in soil is very slow. That there are indeed interactions of ,- and ,-peptides with biological systems, however, can be seen in the following findings: i) organ-specific distribution takes place after intravenous (i.v.) administration in rats, ii) transport through the intestines of rodents has been observed, iii) , -peptides with positively charged side chains (Arg and Lys) settle on cell surfaces, are able to enter into mammalian cells (fibroplasts, keratinocytes, HeLa cells), and migrate into their cell nuclei (and nucleoli), and iv) in one case, it has already been established that a , -peptide derivative can up- and down-regulate gene expression rates. Besides these less sharply definable interactions, it has also been possible to construct , - and , -peptide agonists of naturally occurring peptide hormones, MHC-binding , -peptides, or amphipathic , -peptide inhibitors of membrane-bound proteins in a controlled fashion. Examples include somatostatin mimics and the suppression of cholesterol transport through the intestinal brush-border membrane (by the SR-BI-protein). The results so far obtained from investigations into peptides made up of homologues of the proteinogenic amino acids also represent a contribution to deepening of our knowledge of the natural peptides/proteins, while potential for biomedicinal application of this new class of substances has also been suggested. [source] | ||||||||||||||||