皂甙分离和结构鉴定研究进展

本文对近十年来皂甙分离方法和结构签定技术进行了综述，尤其是对HPLC及1DNMR、2DNMR各种新技术在皂甙分离和结构鉴定方面的应用，作了较为详细的总结。     

Stylissadines A and B: the first tetrameric pyrrole-imidazole alkaloids

[reaction: see text] Pyrrole-imidazole alkaloids are widely distributed in marine sponges of the orders Halichondrida and Agelasida. Chemical investigation of the Caribbean sponge Stylissa caribica led to the isolation of the first tetrameric pyrrole-imidazole alkaloids. The so-called stylissadines are the largest and most complex pyrrole-imidazole alkaloids discovered so far and are therefore a major challenge for the structure determination by NMR spectroscopy. Their isolation and structure elucidation are discussed in detail.     

New cytotoxic cucurbitacins from the pericarps of Trichosanthes tricuspidata fruits

An extract of the fruits of Trichosanthes tricuspidata collected in North Vietnam was found cytotoxic in KB cells. A bioassay-guided fractionation led to the isolation of a series of cucurbitacins of which two are new: tricuspidatin and 2-O-glucocucurbitacin J. Their isolation and structure determination are described.     

Morierinin: a new cytotoxic cucurbitacin from the leaves of Morierina montana Vieill

An extract of the leaves of Morierina montana collected in New Caledonia was found to be cytotoxic for KB cells. A bioassay-guided fractionation procedure led to the isolation of a series of cucurbitacins of which one, morierinin (1), is new. The isolation and structure elucidation of 1 are described.     

Antibiotika aus actinomyceten. Isolierung und konstitution von aklavinon—I und aklavinon—II,zwei neuen anthracyclinonen aus fermentationsansätzen von streptomyces galilaeus

The isolation and structure elucidation of two stereoisomers of aklavinone are reported.     

New Spirostaphylotrichins from Staphylotrichum coccosporum

The isolation and structure elucidation of the new spirostaphylotrichins B ( 2 ), C and D ( 3/4 ), F ( 5 ), Q ( 6 ), and R ( 7 ) are described. Compounds 2 and 3 are artefacts formed during the isolation of the metabolites from the cultures. The absolute configuration of spirostaphylotrichin A ( 1 ) has been determined by CD spectroscopy.     

Phytoecdysteroids of plants of the genus Melandrium

The isolation and determination of the structure of the new phytoecdysteroid melandroside A are described; it is viticosterone E 22-O-α-D-galactopyranoside.     

Novel isolation of phytochemical compositions by phase transition extraction with acetonitrile

Based on the phenomenon that hydrophilic acetonitrile can be separated from water by adding a hydrophobic solvent, a phase transition extraction (PTE) method for isolation of phytochemical compositions was developed. The isolation efficiency of the proposed method was assessed in complete grouping of the constituents in three important traditional Chinese medicine plants. Further study of the PTE for Scutellaria bacalensis Georgi found that the constituents in the organic phase are all flavonoid aglycones while the ones in the aqueous phase are all flavonoid glycosides, revealing the property of high structure selectivity for the proposed PTE process. The effect of using different modifiers on the isolation efficiency was investigated. The results obtained by using non-oxygenated hydrophobic solvents are perfect while those by inorganic salts are acceptable, but those by oxygenated hydrophobic solvents are bad. Subsequent GC analysis revealed that the solvent composition difference between the two separated phases among PTE processes using different types of modifier is responsible for the different isolation results obtained. Finally, the proposed method was proved to be insensitive to both the acetonitrile concentration and the added amount of modifier.     

Acyclic telluroiminium salts: isolation and characterization

The isolation, structure, and reactions of acyclic telluroiminium salts were disclosed. The delocalization of electrons on the tellurium atom and the partial double-bond character of C-Te bonds in the salts are discussed on the basis of X-ray molecular structure analysis, 13C and 125Te NMR spectroscopy, and molecular orbital calculation.     

Signal losses in pesticide analysis using the broadband isolation waveform in a commercial quadrupole ion trap to accomplish precursor ion isolation in tandem mass spectrometry

Signal losses due to precursor ion isolation in a quadrupole-ion-trap mass spectrometer were studied using selected pesticides as model compounds. These signal losses originate from isolations of ion populations employing the broadband isolation (bbiso) waveform used in the Varian quadrupole ion-trap precursor ion isolation protocol. Signal losses were found to be ‘precursor ion structure’ dependent upon isolation using the bbiso. The effect of the bbiso waveform on the ionic structure and nature of substituents on the precursor ion was investigated. Isolation of old electron radical molecular ions of the type [M^+?] showed remarkable signal losses compared with isolation of fragment ions derived from the same compounds. The impact of the bbiso waveform on the response of the instrument using mass spectrometry/mass spectrometry and the bbiso waveform was also examined. The response of the instrument as related to the calculated Instrument Detection Limits was observed to parallel ion population losses.     

Determination of the absolute configuration of peptide natural products by using stable isotope labeling and mass spectrometry

Structure elucidation of natural products including the absolute configuration is a complex task that involves different analytical methods like mass spectrometry, NMR spectroscopy, and chemical derivation, which are usually performed after the isolation of the compound of interest. Here, a combination of stable isotope labeling of Photorhabdus and Xenorhabdus strains and their transaminase mutants followed by detailed MS analysis enabled the structure elucidation of novel cyclopeptides named GameXPeptides including their absolute configuration in crude extracts without their actual isolation.     

Structural Analysis of Eukovoside,A New Phenylpropanoid Glycoside from Euphrasia rostkoviana HAYNE

The isolation and structure determination of a phenylpropanoid glycoside from Euphrasia rostkoviana HAYNE, named eukovoside (1). are reported.     

Quinoline, quinazoline and acridone alkaloids

This review covers the isolation, structure determination, synthesis and biological activity of quinoline, quinazoline and acridone alkaloids from plant, microbial and animal sources; 115 references are cited.     

Quinoline, quinazoline and acridone alkaloids

This review covers the isolation, structure determination, synthesis and biological activity of quinoline, quinazoline and acridone alkaloids from plant, microbial and animal sources: 134 references are cited.     

半纤维素及其结构研究

本文叙述半纤维素的存在、分类、糖基组成及自然界中几种主要半纤维素的化学结构。阐述半纤维素的分离及提纯方法,比较不同方法的优缺点;讨论建立半纤维素化学结构的一般步骤,介绍其化学结构研究的主要手段。     

HPLC and electrophoresis — Competitors or partners

Summary Protein structure analysis is an indispensible tool in modern biological research. However, the isolation of a protein or the separation of peptides in a form suitable for sequence analysis is a considerable technical challenge. The two predominant separation methods in protein biochemistry are chromatography and electrophoresis. In this paper the position, advantaged and disadvantages of both HPLC and electrophoresis for the separation of amino acids, peptides and proteins in protein structure analysis are discussed.     

A new diterpenoid related to eunicellin and cladiellin from a Muricellasp.

The isolation and structure elucidation of a new diterpenoid from a horny-coral (Gorgonaceae) are reported. The ¹H and ¹³C-NMR spectra are discussed.     

New indole-based chromophore-containing main-chain polyurethanes: architectural modification of isolation group, enhanced nonlinear optical property, and improved optical transparency

Three indole-based nonlinear optical (NLO) chromophores with changeable isolation groups were successfully introduced into the polymer backbone to yield a series of main-chain polyurethanes. Thanks to the main-chain structure and the advantages of the indole-based chromophores, all of the polymers show excellent transparency, good processability, thermal stability, and relatively good NLO effects. The obtained experimental results indicated that the polymer backbone, in addition to the linked isolation moieties, could act as isolation spacers in some special cases. The tested NLO results demonstrated that the isolation groups with apparent site-isolation effect might not benefit the macroscopic NLO effect of the resultant polymers.     

Effect of bovine serum albumin on the structure and properties of Langmuir Blodgett films based phosphocholine and cholesterol

Mono- and bilayer Langmuir-Blodgett films based on phosphocholine and cholesterol and prepared by horizontal and vertical deposition are investigated by atomic force microscopy. It was found that bovine serum albumin (BSA) included at the stage of film formation. At the same time, isolation has a considerable effect on their structure. It was shown that the globular formation of nanostructures with heights of 4–7 nm occurs as a result of transferring lipids to a hydrophobic surface from a subphase containing BSA, indicating the reorganization of monolayers during protein isolation and inclusion in its composition.     

Quinoline, quinazoline and acridone alkaloids

This review covers the isolation, structure determination, synthesis and biological activity of quinoline, quinazoline and acridone alkaloids from plant, microbial and animal sources. The literature from July 2001 to June 2002 is reviewed, and 125 references are cited.