CEC and EKC of natural compounds

In this review, an overview of CEC and EKC methods with their developments are summarized for different natural compounds. It is divided into three main parts. The first part elaborates the separation of lipophilic compounds without any charged groups. The second part constitutes CEC and EKC of lipophilic compounds containing ionizable functional groups whereas the third part contains hydrophilic compounds. Packed, monolithic, coated, or raw fused-silica (FS) capillaries are among the choice for stationary phases. Applications of these phases on the above-mentioned three classes of compounds, coupled with different detection methods, e.g. MS or LIF, are explored and their advantages and disadvantages are discussed.     

PMR spectra of natural stilbene compounds

Summary 1. The PMR spectra of 13 natural stilbenes have been studied.2. The dominating role of -electron interaction of the fragments of the stilbene molecule in the screening of the aromatic and olefinic protons has been shown. A series of increments presenting interest for determining the structure of stilbene compounds is proposed.3. It has been established that the nature and nature and number of the substituents in the aglycone part of the molecule have no influence on the screening of the anomeric proton of glycosidated stilbenes, but it does depend on the position of attachment of the carbohydrate fragment.A. A. Zhdanov Irkutsk State University. Irkutsk Institute of Organic Chemistry, Siberian Branch of the Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 3–10, January–February, 1976.     

PMR spectra of natural stilbene compounds

1. The PMR spectra of 13 natural stilbenes have been studied. 2. The dominating role of π-electron interaction of the fragments of the stilbene molecule in the screening of the aromatic and olefinic protons has been shown. A series of increments presenting interest for determining the structure of stilbene compounds is proposed.     

NMR-13C specteoscopy of natural compounds

Russian Chemical Bulletin -     

Chemistry of natural compounds and bioorganic chemistry

The racemic form of the metabolite of theDysidea sea sponge, furanoterpenoid pallescensin A, was synthesized by cationic cyclization of the sulfonyl-substituted linear sesquiterpene precursors. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2060–2064, November, 1997.     

DTA of natural and synthetic uranium compounds

A brief outline of structural considerations is given, concerning compounds one can meet as secondary uranium minerals. The authors report the thermal analysis of minerals deposited at the National Museum Collection in Prague. Three different types of instruments were used: a MOM derivatograph, a Netzsch DTA equipment, and an instrument constructed according to Rosický for microspecimens. The thermal analysis results were correlated with X-ray structure analysis and infrared spectra analysis data. The examples applied were: synthetic rutherfordine and related compounds, synthetic andersonite and the minerals liebigite and schoeckingerite, and synthetic schoepite.

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Zusammenfassung Ein kurzer Bericht über strukturelle Erwägungen bezüglich sekundärer Uraniumerz-Verbindungen wird gegeben. Es werden an die durch thermoanalytische Überprüfung der in der Sammlung des Nationalmuseums zu Prag befindlichen Erze gewonnenen Erfahrungen mitgeteilt. Drei verschiedene Typen von Geräten wurden eingesetzt: der Derivatograph MOM, die DTA-Vorrichtung Netzsch und ein nach Rosický gebautes Gerät für Mikroproben. Die Ergebnisse der Thermoanalyse wurden mit den Daten der Röntgen-Strukturanalyse und denen der Analyse des Infrarotspektrums in Zusammenhang gebracht. Als Beispiele wurden synthetisches Rutherfordin und verwandte Verbindungen, synthetisches Andersonit, sowie die Erze Liebigit und Schoekingerit und synthetisches Schopit verwendet.

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Résumé Un bref rappel sur les considérations structurales concernant les composés que l'on peut rencontrer comme minéraux secondaires d'uranium est donné. Les auteurs ont eu l'intention de faire partager leur expérience acquise lors de la révision des minéraux déposés dans la Collection du Musée National de Prague, à l'aide de l'analyse thermique. Trois types d'instruments ont été utilisés le Derivatograph MOM, l'appareil ATD Netsch et un instrument construit d'après Rosický, pour l'étude de microéchantillons. On a établi une corrélation entre les résultats de l'analyse thermique et ceux obtenus lors des analyses de structures par rayons X et par spectroscopie infrarouge. Les exemples cités concernent la rutherfordine synthétique et les composés analogues, l'andersonite synthétique, ainsi que les minéraux liebigite et schoeckingérite et la schopite synthétique.

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Adhesive compounds based on natural rubber,modified by nitrogen-containing compounds

The possibility of modifying adhesive compounds based on natural rubber by nitrogen-containing adhesion promoters has been studied. It was shown that the properties of modified adhesive compounds based on natural rubber are comparable to those of adhesive compounds based on polychloroprene, as well as that the implementation of the elaborated technology will enable one to obtain high-strength constructions based on different rubbers.     

天然化合物的分子工程研究新进展

分子天然化合物的研究主要指的是在分子水平上得到天然化合物的新方法,即天然产物的遗传工程合成和仿生合成。本文总结和评述了这方面近年来研究所取得的进展。     

Transformation of organic and inorganic compounds in trifluoroacetic acid

It is established that the effectiveness of fluorine-containing acids in the transformation of organic and inorganic substrates is due to the ability of the acid to perform several functions: to accumulate relatively high concentrations of molecular oxygen, to activate it, and to serve as a hydrogen-containing medium.     

Stereochemical aspects of organic sulphur compounds of natural derivation

Selected groups of chiral, tri- and tetra-co-ordinate sulphur compounds are briefly discussed in a historical context. Special attention is given to naturally derived sulphonium salts, sulphoxides, and sulphoximides, and to certain stereochemical problems associated with their structures. The fruitful alliance between biochemistry and stereochemistry, also in studies of sulphur compounds, is emphasized and illustrated. Possible subjects for future studies are adumbrated.     

Antiviral potential of natural compounds against influenza virus hemagglutinin

Influenza virus of different subtypes H1N1, H2N2, H3N2 and H5N1 cause many human pandemic deaths and threatening the people worldwide. The Hemagglutinin (HA) protein mediates viral attachment to host receptors act as an attractive target. The sixteen natural compounds have been chosen to target the HA protein. Molecular docking studies have been performed to find binding affinity of the compounds. Out of the sixteen, three compounds CI, CII and CIII found to posses a higher binding affinity. The molecular dynamics (MD) simulation has been performed to study the structural, dynamical properties for the nine different complexes CI, CII, CIII bound with H1, H2, H3 proteins and the results were compared. The molecular mechanics Poission-Boltzmann surface area (MM-PBSA) method is used to compare the binding free energy, its different energy components and per residue binding contribution. The H1 subtype shows higher binding preference for all the curcumin derivatives than H2 and H3. The binding capability of protein subtypes with curcumin derivatives and the binding affinity of curcumin compounds are in the order H1 > H2 > H3 and CI > CII > CIII respectively. The two -O-CH3- groups present in the CI compound help to have strong binding with HA protein than CII and CIII. The van der Waals interaction energy plays a significant role for binding in all the complexes. The hydrogen bonding interactions were monitored throughout the MD simulation. The conserved region (153–155) and the helix region (193–194) of H1, H2, H3 protein subtypes are found to possess higher binding susceptibility for binding of the curcumin derivatives.     

Chemopreventive effects of natural dietary compounds on cancer development

Chemoprevention, a relatively new and promising strategy to prevent cancer, is defined as the use of natural dietary compounds and/or synthetic substances to block, inhibit, reverse, or retard the process of carcinogenesis. The chemopreventive effects elicited by these natural dietary compounds are believed to include antioxidative, anti-inflammatory activity, induction of phase II enzymes, apoptosis, and cell cycle arrest. Many mechanisms have been shown to account for the anticarcinogenic actions of natural dietary compounds; attention has recently been focused on intracellular-signaling cascades as common molecular targets for various chemopreventive natural dietary compounds. In this critical review, we will summarize current knowledge on natural dietary compounds that act through the signaling pathways and modulate gene expression to induce detoxifying enzymes, programmed cell death, anti-inflammatory, and anti-proliferative effects, thus providing evidence for these substances in cancer chemopreventive action (128 references).     

Behaviour of organoarsenic compounds in contact with natural zeolites

Batch experiments were conducted on aqueous solutions containing arsenite, arsenobetaine, methylarsonic acid or phenylarsonic acid in contact with natural zeolites to examine their interaction. The concentration of the arsenic species in the liquid phase at equilibrium before and after contact was measured by means of liquid chromatography coupled with inductively coupled plasma mass spectrometry detection. Clinoptilolites completely removed arsenobetaine from the solution and the resulting amounts of dimethylarsinic acid were detected. The methylarsonic acid maximum concentration diminution was reached at a mass—to volume V value of m/V = 0.2. Phenylarsonic acid solution decreased its concentration 75% after treatment with clinoptilolites. Untreated mordenites in contact with arsenite solutions led to the formation of arsenate, whereas acid‐washed mordenites practically removed arsenobetaine and were less effective for methylarsonic acid. To show the incompatibility of molecular dimensions with the zeolite windows, the molecular parameters of surface area, molecular volume, molecular length, and the width and depth of arsenite, arsenate and a series of ten organic arsenic compounds were calculated. Since sorption onto the external zeolite surface rather than a sieve process defined the interaction, an acid‐catalysed reaction mechanism is proposed to explain the transformation results. Copyright © 2001 John Wiley & Sons, Ltd.     

Transformation of low-affinity lead compounds into high-affinity protein capture agents

A simple and potentially general approach to the isolation of high-affinity and -specificity protein binding synthetic molecules is presented. A modest affinity lead compound is appended to the end of each molecule in a combinatorial library of oligomeric compounds, such as peptides or peptoids. The library is then screened under conditions too demanding for the lead to support robust binding to the protein target. It was anticipated that this procedure would select for bivalent ligands in which the oligomer library provides both a second binding element as well as an appropriate linker between this element and the lead compound. We report here synthetic ligands for the Mdm2 protein and ubiquitin able to capture their target proteins from dilute solutions in the presence of a large excess of other proteins.     

Transformation of neutral rhenium compounds during electrospray ionization mass spectrometry

Four neutral rhenium compounds were examined by electrospray ionization mass spectrometry. Acetonitrile solutions of (Ind)Re(CO)₃ (Ind = indenyl) and (Cp)Re(CO)₃ (Cp = cyclopentadienyl) gave rise to [Re(CO)₃(CH₃CN)₃]⁺ ions. This is indicative of a reaction with the solvent, although these compounds do not react with acetonitrile under regular laboratory conditions. In contrast, (Ind)Re(CO)₂(butyne) and (Cp)Re(CO)₂(butyne) did not lose their aromatic hydrocarbon ligand upon ionization; the predominant product ions generated upon electrospray ionization were [(Ind)Re(CO)(CH₃CN)(butyne)]⁺ and [(Cp)Re(CO)(CH₃CN)(butyne)]⁺, respectively.     

Preparation and characterization of intercalated misfit-layer compounds and natural superlattices

This paper presents the preparation and characterization of the new types of misfit-layer compounds and natural superlattices consisting of Ce_xNb_1−x−y□_yS (Q′) and Ni_zNbS₂ (H) layers, where □ is an atomic deficit at a metal site. A Q′ layer is larger by about 1 Å in thickness than a CeS (Q) layer in (CeS)_1.16NbS₂. They are prepared by chemical vapor transport reaction in a closed silica tube under quasi-equilibrium conditions. The 1Q′/3H type of compound are grown as a single crystal while the 1Q′/4H type of compound is grown as composite crystals with the 1Q′/3H and 1Q/2H compounds. Natural superlattices which have a long period in a direction perpendicular to layers are found. Their chemical formulae are given by (Ce_xNb_1−x−y□_yS)_m(Ni_z)_n−m(NbS₂)_n, where m and n are integers. It is found from an X-ray-photoelectron spectroscopy (XPS) study that Nb affects the valence and the bonding of Ce in the Q′ layers. It is in a higher oxidation state than Nb in NbS₂ layers. A scanning tunneling microscope (STM) study shows that some of the superlattices form a hexagonal supercell in the (a,b)-plane and behave as a narrow-gap semiconductor so that no STM images are obtained at bias voltage less than 0.3 eV.     

利用天然手性源合成复杂手性化合物的方法

利用天然手性源来合成一些复杂的手性化合物,其合成策略往往具有很高的艺术性.本文主要对糖类和甘露糖以及一些氨基酸类天然产物作为合成子来合成手性分子的一些新方法作了报道.