Determination of <Emphasis Type="Italic">p</Emphasis>-nitrobenzene-azo-naphthol by an oscillating chemical reaction using the analyte pulse perturbation technique

A simple analytical method for the determination of p-nitrobenzene-azo-naphthol was proposed by a sequential perturbation with different amounts of p-nitrobenzene-azo-naphthol on an oscillating chemical system. The method involves a Cu(II)-catalysed oscillating reaction between hydrogen peroxide and sodium thiocyanate in alkaline medium with the aid of continuous-flow stirred tank reactor (CSTR). A good linear relationship between the changes, oscillation amplitude or/and period, and the concentration of p-nitrobenzene-azo-naphthol was obtained. The use of analyte pulse perturbation technique provides a possibility of sequential determination in a same oscillating system, due to a new steady state that reappeared rapidly after each perturbation. The calibration curve fits a linear equation very well when the concentration of p-nitrobenzene-azo-naphthol ranging from 5.2×10⁻⁷ to 3.3×10⁻³M. Influence of temperature, injection point, flow rate and reactants variables on this system were investigated in detail.     

Chemotaxonomy of <Emphasis Type="Italic">Ballota</Emphasis> Species

Sixteen taxa of Ballota were investigated by analyzing the contents of diterpenoid and flavonoid compositions, and the relationships were compared with their morphological properties. HPLC chromatograms of diterpenoids and flavonoids from acetone extracts of sixteen Ballota taxa revealed the presence of thirteen compounds. Isolated compounds from Ballota species were evaluated by the unweighted pair-group arithmetic average (UPGMA) clustering method. B. glandulosissima is distinct from all other taxa in the dendogram, and this species is morphologically different from other taxa by having a high number of glandular hairs. The second group is composed of B. saxatilis ssp. saxatilis and B. inaequidens; these two species are in close kinship as evidenced by their morphology (similar calyx shape). In the latter clusters at most, the affinities among taxa, as suggested by diterpenoid and flavonoid pattern, are only partially congruent with affinities based on other evidence. In general, morphologic, anatomic characters, distributions, and habitats are not concordant with the clusters. Also, no concordance was found between the sections, phylogenetic order [1], and those of the groups formed by cluster analyses.__________Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 242–244, May–June, 2005.     

Identification of five <Emphasis Type="Italic">Listeria</Emphasis> species based on infrared spectra (FTIR) using macrosamples is superior to a microsample approach

Microorganisms can be identified using both macrosamples and microsamples based on infrared spectra (FTIR). This work compares the identification of the five closely related Listeria species L. innocua, L. ivanovii, L. monocytogenes, L. seeligeri, and L. welshimeri using both methods. The overall identification success for 25 strains was 92.8% for the former and 79.2% for the latter methods, respectively. The worst performances of the microsample method were obtained for L. innocua, L. ivanovii, and L. monocytogenes, while L. seeligeri and L. welshimeri did not show significant differences between the techniques. Identification success was mainly influenced by the age of the cells and the spatial heterogeneity of the microcolonies, as analyzed by the microsample method. Spectra of Listeria cells near the stationary phase exhibited more species-specific markers and thus allowed for better discrimination than spectra of growing cells. Furthermore, the heterogeneity of cell composition at different locations in microcolonies of L. innocua, L. ivanovii and L. monocytogenes resulted in limited discrimination success of the microsample method. We conclude that, at least in the case of Listeria, the macrosample method is superior to the microsample method, although the latter is the faster technique.     

Voltammetric determination of the trace amounts of bromate in drinking water after pre-concentration on hydrous γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

A differential pulse voltammetric (DPV) method for the determination of bromate in drinking water, after pre-concentration on γ-Al₂O₃, is proposed. The reduction peak of bromate has been observed at the potential E _p -−1.6 V in an ammonia buffer as a supporting electrolyte. The method has been successfully applied to determine a bromate concentration of 2.5 μg·l⁻¹ in drinking water (RSD=6.1%, n=7). A sample pre-treatment with a column filled with mixed cation-exchange resin in Ag, Ba and H forms was needed before pre-concentration of bromate on alumina.     

Synthesis of cross-linked poly (<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) microparticles in supercritical carbon dioxide

Herein, we report a new method that has been developed to prepare thermoresponsive polymers. The white, dry, fine powders were obtained directly from cross-linking polymerization of N-isopropylacrylamide in supercritical carbon dioxide (scCO₂) with N,N-methylenebisacrylamide as a cross-linker. The effects of the reaction pressure and time as well as the initial concentrations of the initiator, cross-linker, and monomer on the yield and morphology of the resulting polymer were investigated systematically. The polymer yield was increased with the concentrations of the cross-linker, monomer, and reaction time. Under the condition of using higher cross-linker concentrations, the cross-linked poly (N-isopropylacrylamide) microparticles with diameters of 50 nm were generated in scCO₂ in high-yield and short reaction times. These results suggest that the synthetic method using scCO₂ can be used to prepare biomedical materials such as the controlled drug-release system.     

Synthesis and aggregation behavior of <Emphasis Type="Italic">N</Emphasis>-succinyl-o-carboxymethylchitosan in aqueous solutions

A simple and novel method was developed to successfully synthesize N-succinyl-O-carboxymethylchitosan (NSOCMCS) using N-acylation of chitosan with succinic anhydride. The NSOCMCS structure was characterized by Fourier transform infrared and ¹H nuclear magnetic resonance. The aggregation behaviors of NSOCMCS were studied using fluorescence spectroscopy, dynamic light scattering, and atomic force microscopy techniques. The critical aggregation concentration of NSOCMCS in water was determined to be 0.2–0.3 mg/ml. The apparent hydrodynamic radium of an NSOCMCS aggregate was dependent on the concentration. The aggregates demonstrated a much swollen association conformation in aqueous solution. The possible aggregation mechanisms for the NSOCMCS in water are discussed. Moreover, a driving force to form an open aggregation morphology was revealed in this study. Aggregation behaviors are important physicochemical properties of NSOCMCS, which impact the potential application in the biomedical field.     

Syntheses of (<Emphasis Type="Italic">E</Emphasis>)- and (<Emphasis Type="Italic">Z</Emphasis>)-3-styrylchromones

Several (E)- and (Z)-3-styrylchromones were prepared by two different methodologies, the Wittig reaction of chromone-3-carboxaldehyde with benzylic ylides and the Knoevenagel condensation of chromone-3-carboxaldehyde with phenylacetic acids in the presence of potassium tert-butoxide under microwave irradiation. The Knoevenagel reaction followed by a decarboxylation offered an efficient and diastereoselective method for preparing (E)-3-styrylchromones in a shorter reaction time. It was also demonstrated that phenylacetic acid can also be substituted with success by phenylmalonic acid. The stereochemistry of all products was assigned by NMR experiments. Correspondence: Artur M. S. Silva, Chemistry Department, University of Aveiro, 3810-193 Aveiro, Portugal.     

Synthesis of substituted benzoxazinylthieno[2,3-<Emphasis Type="Italic">b</Emphasis>]pyridines by the reaction of (3-cyanopyridin-2-ylthio)acetic acids or their amides with <Emphasis Type="Italic">o</Emphasis>-aminophenyl(diphenyl)carbinol

A general method for the synthesis of 3-amino-2-(4,4-diphenyl-4H-3,1-benzoxazin-2-yl)thieno[2,3-b]pyridines was proposed. The method involves reactions of (3-cyanopyridin-2-ylthio)acetic acids or their amides with o-aminophenyl(diphenyl)carbinol in nitromethane in the presence of perchloric acid followed by neutralization of the resulting salts.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2759–2762, December, 2004.     

A simple synthesis of (±)-2,6-dimethylocta-5(<Emphasis Type="Italic">Z</Emphasis>),7-diene-4-ol and its attractant activity for the bark beetle <Emphasis Type="Italic">Ips typographus</Emphasis>

A simple method for the synthesis of (±)-2,6-dimethylocta-5(Z),7-diene-4-ol possessing a high pheromone activity for the bark beetle Ips typographus was developed.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2245–2247, October, 2004.     

Reaction sites of <Emphasis Type="Italic">N,N′</Emphasis>-substituted <Emphasis Type="Italic">p</Emphasis>-phenylenediamine antioxidants

The geometries of N,N′-diphenylbenzene-1,4-diamine (DPPD), N-phenyl-N′-(1-phenylethyl)benzene-1,4-diamine (SPPD), N-(4-methylpentan-2-yl)-N′-phenylbenzene-1,4-diamine (6PPD), N-propan-2-yl-N′-phenylbenzene-1,4-diamine (IPPD), N-(2-methoxybenzyl)-N′-phenylbenzene-1,4-diamine (MBPPD), and N-phenyl-N′-(2-phenylpropan-2-yl)benzene-1,4-diamine (CPPD) as well as of their dehydrogenation products were optimized by the semiempirical AM1 method. The results support the idea of stable N_B=C_X structures formation during the consecutive dehydrogenation of SPPD, 6PPD, IPPD, and MBPPD antioxidants. The biradicals formed during the second step of dehydrogenation of substituted phenylenediamines might be important for their antioxidant effectiveness. Dedicated to Professor Vladimír Kvasnička, DrSc., in honour of his 65th birthday     

Oxidation of α-methylstyrene on an MCM-22 encapsulated (<Emphasis Type="Italic">R,R</Emphasis>)-(−)-<Emphasis Type="Italic">N,N′</Emphasis>-bis(3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butylsalicylidene)-1,2-cyclohexanediaminocobalt(II) catalyst

(R, R)-(−)-N, N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminocobalt(II) was encapsulated into MCM-22 using the zeolite synthesis method. The encapsulated catalyst proved to be active in the oxidation of α-methylstyrene with NaOCl with higher specific activity than the homogeneous catalyst. At the same time, this encapsulated catalyst was completely inactive in the hydrolytic kinetic resolution of racemic styrene oxide. This observation is in a good correlation with the assumption of the cooperative bimetallic mechanism proposed by Annis and Jacobsen.     

RuO<Subscript>4</Subscript>-mediated oxidation of<Emphasis Type="Italic">N</Emphasis>-benzylated tertiary amines. Are amine<Emphasis Type="Italic">N</Emphasis>-oxides and iminium cations reaction intermediates?

N-Benzylmorpholine,-piperidine, and-pyrrolidine (1A-C, resp.) are oxidised by RuO₄ (generated in situ) at both endocyclic and exocyclic (benzylic) N—α-methylene positions to afford lactams (and dioxo-derivatives) and benzaldehyde (and benzoyl derivatives), respectively. The N-oxides of 1A-C, formed by a minor side reaction, are not involved as intermediates. Control experiments showed the transient formation of endo- and exocyclic iminium cations trapped with NaCN as the corresponding nitriles. The proposed course of the RuO₄-mediated oxidation of 1A-C involves the consecutive steps 1⇒iminium cations+cyclic enamine⇒oxidation products. The endocyclic/exocyclic regioselectivity of the oxidation reaction lies between 0.8 (for 1A) and 2.1 (for 1B). The amine cation radical and the N-α-C· carbon-centered radical seem not to be involved.     

Research on the strong transglycosylation activity in <Emphasis Type="Italic">Aspergillus niger</Emphasis>

Aspergillus niger M-1 strain shows strong transglycosylation activity. A gene of it was introduced into Escherichia coli, and isomalto-oligosaccharides were isolated by a chemical enzymatic method in order to measure the transglycosylation activity. Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 606–607, November–December, 2008.     

Synthesis of magnesium catecholate and <Emphasis Type="Italic">o</Emphasis>-semiquinone complexes by oxidation of the metal with 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">o</Emphasis>-benzoquinone

Oxidation of amalgamated magnesium metal with 3,6-di-tert-butyl-o-benzoquinone (1) in different aprotic organic solvents afforded magnesium catecholate and bis-o-semiquinolate complexes. The catecholate derivatives of magnesium CatMgL₂ (Cat is the 3,6-di-tert-butyl-o-benzoquinone dianion, L = THF or Py) were synthesized in high yields in pyridine and tetrahydrofuran, respectively. The reactions in diethyl ether or dimethoxyethane produced hexacoordinated metal bis-o-semiquinolates SQ₂MgL_n (SQ is the 3,6-di-tert-butyl-o-benzoquinone radical anion, L = Et₂O, n = 2; L = DME, n = 1). The reaction with the use of toluene as the solvent gave a magnesium bis-o-semiquinolate complex containing the coordinated unreduced o-quinone molecule. The molecular structures of the [CatMgPy₂]₂ and SQ₂Mg·DME complexes were established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 92–98, January, 2007.     

Isolation and identification of flower oil components from four <Emphasis Type="Italic">Staphylea</Emphasis> L. species

Chemical composition of the hydrodistilled volatile fraction from flowers of four Staphylea L. species (Staphylea colchica Stev., Staphylea elegans Zab., Staphylea holocarpa Hemsl., Staphylea pinnata L.) was determined by the GC/MS method. Compounds in fresh and dried flowers (stored for 1 year) were determined. Mostly, structures of different oxygenated aliphatic hydrocarbons in all four species were found. Different aldehydes, ketones, esters of higher fatty acids, and hexadecanoic acid were identified, with dominating content of tricosane, hexadecanoic acid and also of heneicosane, pentacosane, heptacosane, and nonacosane. In S. pinnata L. (fresh flowers) some nonaliphatic hydrocarbons, and in S. holocarpa Hemsl. (fresh flowers) esters of higher fatty acids were found.     

Removal of <Superscript>60</Superscript>Co<Superscript>2+</Superscript> and <Superscript>137</Superscript>Cs<Superscript>+</Superscript> ions from low radioactive solutions using <Emphasis Type="Italic">Azolla caroliniana</Emphasis> willd. water fern

This study concerns the removal of the ¹³⁷Cs⁺ and ⁶⁰Co²⁺ β+γ-radioactive ions in Azolla caroliniana Willd. water fern. The living fern and two different types of biosorbent prepared from Azolla caroliniana were tested to remove the above-mentioned radioactive ions from dilute solutions, in the absence and in the presence of the ionic competition. Effective ¹³⁷Cs⁺ and ⁶⁰Co²⁺ ions removal from low radioactive wastewaters was demonstrated. The time dependent K _d (t) values were calculated from the absorption data. These results indicate that removal process achieved equilibrium in about 120 min and that it involves two steps: rapid and slow absorption; the active process (metabolic bioaccumulation on the living fern) was responsible for above one half of the total removal process. A thin layer radiochromatography study leads to the conclusion that the biochemical components in which ¹³⁷Cs⁺ and ⁶⁰Co²⁺ place themselves are of a polysaccharide and lipoid fractions.     

Synthesis of Hexahydro-<Emphasis Type="Italic">1H</Emphasis>-pyrido[3,2-<Emphasis Type="Italic">c</Emphasis>]azepines as Hypotensive Agents of Expected Calcium-Channel Blocking Activity

Summary. Michael addition reaction of 3-(4-fluorophenylamino)-2-cyclohexenone and its 5,5-dimethyl derivative to the acrylonitrile derivatives afforded the novel hexahydroquinolines. The target hexahydro-1H-pyrido[3,2-c]azepine derivatives were obtained via ring enlargement of the corresponding hexahydroquinolines under Schmedt conditions. Some novel pyrido[3,2-c]azepines showed hypotensive activity in vivo on normotensive anaesthetized male adult albino rats and their effects on the ventricular contraction and auricular rate of isolated rabbit hearts using Langendorff’s method and nefidipine as a reference drug were studied. Compounds 29 and 36 which bear some structural similarities to nefidipine exhibited the highest hypotensive activity and negative inotropic as well as chronotropic activities.     

Tandem transformations of tetrahydropyrrolo[3,2-<Emphasis Type="Italic">c</Emphasis>]pyridines under the action of dimethyl acetylenedicarboxylate. A novel route to pyrrolo[2,3-<Emphasis Type="Italic">d</Emphasis>]azocines

Reactions of substituted tetrahydropyrrolo[3,2-c]pyridines with dimethyl acetylenedicarboxylate in protic and aprotic solvents were studied. A novel single-step method for the synthesis of pyrrolo[2,3-d]azocine derivatives was developed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2513–2519, November, 2005.     

Binding of nontarget microorganisms from food washes to anti-<Emphasis Type="Italic">Salmonella</Emphasis> and anti-<Emphasis Type="Italic">E. coli</Emphasis> O157 immunomagnetic beads: most probable composition of background Eubacteria

We present herein the composition of bacterial communities occurring in ground chicken and the changes which arise in these populations based upon nonselective partitioning by commercially-available Dynal anti-Salmonella and anti-E. coli O157 immunomagnetic beads (IMB). Our enumeration and colony selection protocol was based upon a 6 × 6 drop plate method (n = 18 for each 25-g sub-sampling) using a dilution which resulted in ca. 4–8 colonies per drop. An average of 82 ± 13 colonies were selected from three 25-g ground chicken subsamplings per batch, each of which was repeated seasonally for one year. DNA was extracted from each colony and the composition of Eubacteria in each of these harvests was determined by sequence-based identification of 16S rDNA amplicons. The Gram-positive bacteria Brochothrix thermosphacta and Carnobacterium maltaromticum were the most commonly found organisms in both the total chicken wash (PBS) and in the IMB-bound (PBS-washed) fractions. The remaining background organisms which also adhered to varying degrees to commercial IMBs were: Pseudomonas oleovorans, Acinetobacter lwoffi, Serratia spp., and one Rahnella spp. A large number of the organisms were also cladistically evaluated based on rDNA basepair disparities: all Brochothrices were monophyletic; twelve different Pseudomonads were found along with eight Carnobacteria, seven Acinetobacteres, four Serratiae, and two Rahnellae. Carnobacterium alone showed an IMB-based concentration enhancement (ca. two to sixfold). Any reference to a brand or firm name does not constitute endorsement of the US Department of Agriculture over others of a similar nature not mentioned