用层析法分离磷酸酯基化学修饰的二核苷酸的非对映异构体

本文报道用高效液相色谱法和高效薄层色谱法分离磷酸醌基化学修饰的二核苷酸二尿苷硼烷磷酸酯，二胸苷硫代磷酸酯，二（２＇－脱氧－２＇－氟）尿苷及胞苷硫代磷酸酯的非对映异构体，所得到的非对映异构体的ＲＦ值和＾３１Ｐ－ＮＭＲ化学移植之间的关系符合一般规律，即移动快的异构体有较高的位移植，移动慢的异构体有较的化学位移植。     

Determination of chlorogenic acid,polyphenols and antioxidants in green coffee by thin‐layer chromatography,effect‐directed analysis and dot blot – comparison to HPLC and spectrophotometry methods

The great prevalence of thin‐layer chromatography over high‐performance liquid chromatography is connected with the possibility of analyzing many samples in parallel. Therefore, the method is often used in screening and/or effect directed analysis to compare composition and chemical/biological properties of many samples in one run. It was already proved, that high performance thin‐layer chromatography, in many cases, can replace high‐performance liquid chromatography for quantitative analysis. The main aim of the paper is to show that simple thin‐layer chromatography can also be used as a quantitative or at least as a semi‐quantitative method, even when it concerns effect directed analysis e.g. direct bioautography. Chlorogenic acid content was measured in four methanol extracts of various green coffees and in one extract of black coffee using thin‐layer chromatography with ultraviolet detection and thin‐layer chromatography with effect directed detection. High‐performance liquid chromatography was used as a reference method. Additionally, total contents of polyphenols and antioxidants were estimated using thin‐layer chromatography or dot‐blot on chromatography plates. These results were compared to spectrophotometric methods. It was proved that thin‐layer chromatography can be used as a quantitative (using densitometry) or semi‐quantitative method (using other detection methods including effect directed detection) as well as for estimating total antioxidants or polyphenols content.     

Characterization of polycyclic aromatic hydrocarbons and hydroaromatics in a distillable coal-derived solvent by chromatographic and corrected fluorescence methods

Polycyclic aromatic hydrocarbons and hydroaromatics were separated from a coal-derived distillate by dry-column chromatography and high-performance liquid chromatography. Individual components in the isolated fractions were characterized by corrected excitation fluorescence spectrometry. With the chromatographic data and the fluorescence data, compound identification was possible in some cases.     

Reactions of polystyryl anions with carbon dioxide and oxygen. Analysis of products by silica gel chromatography

Polystyryllithium was prepared by anionic polymerization. This “living polymer” and the polystyrylmagnesium bromide derived from it were treated with carbon dioxide (solid or gas). The highest yields of carboxylic acid were obtained when solid carbon dioxide was used with polystyryllithium or by treatment of polystyrylmagnesium bromide with gaseous carbon dioxide. The products from the reaction of polystyryllithium with oxygen were polymeric ketone X, the alcohols IXa and IXb, and coupling products (e. g., XI). The various functionalized and unfunctionalized polystyrene products were isolated by chromatography on silica gel and were characterized by gel permeation chromatography (GPC), thin layer chromatography (TLC), and high-performance liquid chromatography (HPLC) in combination with chemical transformations.     

Modern approaches for determination and identification of barrenwort (<Emphasis Type="Italic">Epimedium</Emphasis>) flavonoids

The modern methods of analysis of the main active substances barrenwort (Epimedium)—flavonoids—are considered. Various types of extraction are used to isolate these components from plant raw materials. Flavonoids are separated by capillary electrophoresis, thin layer chromatography, and high performance liquid chromatography (HPLC) in combination with UV and mass spectrometric detection.     

Use of mode mixing to determine the optic tensor configuration of a thin ferroelectric liquid crystal layer

It is possible to probe directly the optic tensor profile within a thin ferroelectric liquid crystal layer by the propagation of prism-coupled leaky guided modes. Plane parallel monochromatic radiation of single polarization is made incident through a prism into a planar ferroelectric liquid crystal layer. Monitoring the reflected signal as a function of incident angle results in a series of sharp dips at angles corresponding to the excitation of modes in the layer. For a ferroelectric layer in which there is in-plane or out-of-plane tilt, conversion of one linear polarization to the orthogonal polarization may occur, by detecting this conversion it has been possible to show the existence of thin boundary regions at the two surfaces of the thin ferroelectric liquid crystal layer.     

Characterization of commercial soybean products by conventional and perfusion reversed-phase high-performance liquid chromatography and multivariate analysis

Conventional and perfusion reversed-phase high-performance liquid chromatography are used to characterize commercial soybean products for human consumption. For this purpose, previously optimized methods of conventional and perfusion chromatography applied to the separation of soybean proteins are employed. Sixty different samples corresponding to 26 different trademarks of soybean products [soybean protein isolate, soybean flour, textured soybean, soybean milks (liquid and powdered), and soybean infant formulas] are analyzed. Characterization of soybean products is carried out on the basis of their protein profiles obtained by both chromatographic methods. Data obtained are processed using multivariate methods such as principal components and discriminant analysis. Perfusion chromatography enables a further and faster characterization of commercial soybean products than conventional chromatography, of great value in the quality control of this kind of product.     

Use of mode mixing to determine the optic tensor configuration of a thin ferroelectric liquid crystal layer

Abstract

It is possible to probe directly the optic tensor profile within a thin ferroelectric liquid crystal layer by the propagation of prism-coupled leaky guided modes. Plane parallel monochromatic radiation of single polarization is made incident through a prism into a planar ferroelectric liquid crystal layer. Monitoring the reflected signal as a function of incident angle results in a series of sharp dips at angles corresponding to the excitation of modes in the layer. For a ferroelectric layer in which there is in-plane or out-of-plane tilt, conversion of one linear polarization to the orthogonal polarization may occur, by detecting this conversion it has been possible to show the existence of thin boundary regions at the two surfaces of the thin ferroelectric liquid crystal layer.     

Phytochemical analysis of traditional Chinese medicine using liquid chromatography coupled with mass spectrometry

Traditional Chinese medicine (TCM) is commonly considered to operate due to the synergistic effects of all the major and minor components in the medicines. Hence sensitive and comprehensive analytical techniques are needed to acquire a better understanding of the pharmacological basis of the herb and to enhance the product quality control. The present review mainly focuses on the phytochemical analysis of TCMs using high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS). Atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) are the two commonly used ion sources. Triple quadrupole, ion trap (IT), Fourier transform ion cyclotron resonance (FTICR) and time-of-flight (TOF) mass spectrometers are used as on-line analyzer. The relationship between structural features and fragmentation patterns should be investigated as thoroughly as possible and hence be applied in the on-line analysis to deduce the structures of detected peaks. Characteristic fragmentation behaviors of the reference standards, as well as information regarding polarity obtained from retention time data, on-line UV spectra, data from the literature and bio-sources of the compounds allowed the identification of the phytochemical constituents in the crude extracts. Although a mass spectrometer is not a universal detector, high-performance liquid chromatography coupled with multistage mass spectrometry (HPLC-MS(n)) technique was still proved to be a rapid and sensitive method to analyze the majority of the many constituents in herbal medicines, particularly for the detection of those present in minor or trace amounts. The methods established using HPLC-MS techniques facilitate the convenient and rapid quality control of traditional medicines and their pharmaceutical preparations. However, the quantitative analysis is not the topic of this review.     

Qualitative and quantitative analysis of Alpiniae Oxyphyllae Fructus by high-performance liquid chromatography coupled to Fourier transform-ion cyclotron resonance mass spectrometry

Alpiniae Oxyphyllae Fructus, as a homology of medicine and food, has been widely used in China for thousands of years. However, the existing qualitative and quantitative methods are difficult to evaluate the quality of Alpiniae Oxyphyllae Fructus samples from multiple sources. In this paper, an high-performance liquid chromatography fingerprint was established for assessing the quality of Alpiniae Oxyphyllae Fructus from different areas. Then, high-performance liquid chromatography was coupled to Fourier transform-ion cyclotron resonance mass spectrometry for characterization of the chemical compositions in Alpiniae Oxyphyllae Fructus. In fingerprint analysis, 54 common peaks were confirmed and six chromatographic peaks of them were identified. The similarity of 14 samples from different areas was between 0.990 and 1.000. Moreover, a total of 30 chemical components were characterized by high-performance liquid chromatography coupled to Fourier transform-ion cyclotron resonance mass spectrometry method, six compounds of which were decisively identified. Finally, the content of nootkatone was determined by high-performance liquid chromatography. In conclusion, the methods used in this study are efficient for qualitative and quantitative analysis of Alpiniae Oxyphyllae Fructus. Also, these methods can be used to control the quality of other traditional Chinese medicines.     

Isolation of bioactive allelochemicals from sunflower (variety Suncross-42) through fractionation-guided bioassays

Plants are rich source of biologically active allelochemicals. However, natural product discovery is not an easy task. Many problems encountered during this laborious practice can be overcome through the modification of preliminary trials. Bioassay-directed isolation of active plant compounds can increase efficiency by eliminating many of the problems encountered. This strategy avoids unnecessary compounds, concentrating on potential components and thus reducing the cost and time required. In this study, a crude aqueous extract of sunflower leaves was fractionated through high performance liquid chromatography. The isolated fractions were checked against Chenopodium album and Rumex dentatus. The fraction found active against two selected weeds was re-fractionated, and the active components were checked for their composition. Thin layer chromatography isolated a range of phenolics, whereas the presence of bioactive terpenoids was confirmed through mass spectroscopy and nuclear magnetic resonance spectroscopy.     

Non-volatile products of triolein produced at frying temperatures characterized using liquid chromatography with online mass spectrometric detection.

Oxidation products from triolein under model heated frying conditions have been analyzed using liquid chromatography with an evaporative light scattering detector and atmospheric pressure chemical ionization (APCI) mass spectrometric detection. Triolein was heated at 190 degrees C with 2% water added each hour, to simulate the moisture of a frozen product, until polar components reached approximately 30%. The samples were separated using reversed-phase high-performance liquid chromatography with APCI-MS detection. Triolein oxidation products included hydroperoxides, epoxides and a ketone. Other products were formed by shortening of an acyl chain on the intact triolein. Normal and oxygen-containing products formed by the dimerization of triolein were also observed. Other products included chain addition products formed by addition of acyl chain subunits to intact triolein to form higher molecular weight products.     

A review of chromatographic methods for the assessment of phospholipids in biological samples

Phospholipids are important constituents of all living cell membranes. Lipidomics is a rapidly growing field that provides insight as to how specific phospholipids play roles in normal physiological and disease states. There are many analytical methods available for the qualitative and quantitative determination of phospholipids. This review provides a summary of the methods that were historically used such as thin layer chromatography, gas chromatography and high-performance liquid chromatography. In addition, an introduction to applications of interfacing these traditional chromatographic techniques with mass spectrometry is provided.     

Improved quantitation of 2,4-dichlorophenol in plant tissues by high-performance liquid chromatography with amperometric detection

For the determination of 2,4-dichlorophenol (DCP) residues in plant tissues, the use of high-performance liquid chromatography with amperometric detection decreases the quantitation limits by a factor of five compared to those obtained with gas chromatography with Hall conductivity detection. It also avoids the clean-up and derivatization procedures required for electron-capture detection. After extraction of DCP from plant tissue by steam distillation and collection in toluene, an alumina clean-up column is used to remove electroactive interferences from the samples. The DCP is then extracted into aqueous alkaline solution, neutralized, and diluted with acetonitrile to ca. 50% (v/v). An alternative clean-up made use of an in-line, pre-column electrochemical procedure, in which case the alumina column was not used. The components were separated with a reverse-phase column and detected with a polychlorotrifluoroethylene/graphite composite electrode at an applied potential of +1.0 V vs. Ag/AgCl. The quantitation limit for DCP in the plant tissues was 100 pg per injection (0.05 mg Kg^?1).     

Application of analytical chemistry in the quality evaluation of Glycyrrhiza Spp

Licorice, one of the oldest traditional Chinese medications, is widely used in the treatment of various diseases. With the development of science and technology, an increasing amount of analytical techniques have been applied to the quality control of licorice. Herein, we summarize several of the quality control methods developed in recent years. These approaches include sample preparation processes, high-performance thin layer chromatography, gas chromatography, gas chromatography/mass spectrometry, high-performance liquid chromatography, and liquid chromatography/mass spectrometry (LC/MS). Among these various techniques, LC/MS has come forward as one of the main methods forquality control of licorice.     

云南植物——露水草中的一种新植物甾酮的分离与分析

云南植物露水草富含植物甾酮类成分。为了研究其中的生物活性成分,采用多种色谱分离方法(氧化铝柱色谱、硅胶柱色谱、常压反相C18柱色谱、制备薄层色谱及反相高效液相色谱等)相结合,从露水草中分离得到一种新植物甾酮。综合一维和二维核磁共振光谱以及电喷雾质谱数据分析,确定该化合物的结构为3β,4α,14α,20R,22R,25-hexahydroxy-5α-cholest-7-en-6-one,为一种较为少见的具有5α-H的植物甾酮。     

Unexpected photolysis of the sunscreen octinoxate in the presence of the sunscreen avobenzone

A major concern raised about photostability studies of sunscreen products is that the photodegradation of sunscreens does not readily translate into changes in product performance. This study examines the correlation between photochemical degradation of sunscreen agents and changes in protection provided by sunscreen films. Films of a commercial sunscreen product containing avobenzone, oxybenzone and octinoxate were irradiated using a fluorescent UV-A phototherapy lamp with additional UV-B blocking filter. Periodically, during irradiation the transmittances of the films were measured and samples collected for chemical analysis of the sunscreen agents using high-performance liquid chromatography techniques. The results show that UV-induced changes in UV transmittance of sunscreen films correlate with changes in concentration of sunscreen agents. In a parallel experiment, we also irradiated a thin film of the same product in the cavity of an electron spin resonance (ESR) spectrometer. We report the concomitant photolysis of avobenzone and octinoxate that predominates over expected E/Z photoisomerization and that irradiation of a film of this product produced free radicals detected by ESR spectroscopy that persisted even after exposure had ended.     

Application of Thin Layer,Ion Exchange and High Performance Liquid Chromatography to Separate Pharmacologically Active Components of an African Arrow Poison of Plant Origin

Abstract

We have applied thin layer chromatography (TLC), ion exchange chromatography (IEC) and, high performance liquid chromatography (HPLC) to separate and identify the pharmacologically active components of an african arrow poison of plant origin. On the basis of Rf values obtained from TLC, the active components of the toxin are unlike d-tubocurarine, atropine and, scopolamine. Dowex 1 × 2 IEC of 630 mg of crude toxin on a 2.5″ × 33″ column with step gradient elution (NaCl, 0.1 - 1. OM and NaOH, 0.1M) led to the identification of three distinct peaks. When the components of each of the three peaks were subjected to HPLC, the results confirmed the homogeneity of each of the isolated peaks except for the third peak which was a doublet.     

来源于类芽孢杆菌属碱性甲壳素酶的分离纯化及其性质

甲壳素,又名几丁质(chitin),是自然界中含量仅次于纤维素的第二大天然多糖,有第六生命要素之美称.其主要存在于甲壳类动物的外壳、真菌细胞的细胞壁以及一些昆虫的外壳中,每年自然界中约有100多亿吨甲壳素生成.甲壳素是由2-乙酰氨基-2-脱氧-D-吡喃葡萄糖和2-氨基-2-脱氧-D-吡喃葡萄糖通过β-1,4糖苷键连接而成的二元线性聚合物,分子链中分布许多羟基、氨基及乙酰氨基,形成大量分子间及分子内氢键,致使其结晶度较高,化学性质十分稳定,直接利用较为困难.甲壳素不溶于稀酸、稀碱以及一般有机溶剂,工业上常用强酸强碱法处理甲壳素,以制备壳寡糖类产品,但该方法具有产品结构不单一,环境污染较为严重等缺点.甲壳素酶可特异性水解甲壳素链中β-1,4糖苷键,得到甲壳寡糖和N-乙酰氨基葡萄糖.酶解法降解甲壳素工艺简单、反应条件温和、环境友好,有很好的应用前景.我们以Paenibacillus pasadenensis CS0611为出发菌株,以蟹壳粉末为培养基唯一碳源及氮源,在适宜条件下培养48 h.发酵液经离心、硫酸铵(80％饱和度)盐析、透析除盐后得到粗酶液.再利用HiTrap DEAE FF离子交换层析和HiLoad 26/600Superdex 200 pg凝胶过滤层析对该粗酶液进行分离纯化,以得到电泳纯甲壳素酶.所制备甲壳素酶比活力为10.28 U/mg,最终纯化倍数为5.3,酶活得率为15.7％.SDS-PAGE结果表明,该甲壳素酶相对分子质量约为69 kDa.后经MALDI-TOF-MS鉴定,该酶部分肽段和来源于另一株Paenibacillus pasadenenss的甲壳素酶(accession No:gi655151624)具有较高的同源性,进一步证实所纯化蛋白为甲壳素酶.对上述纯化的甲壳素酶的酶学性质进行研究,结果发现:其最适反应温度为50℃,在20-35℃内有较好的稳定性,50℃及以上热稳定性较差;最适pH为5.0,在pH4.0-11.0间具有较高稳定性,表明该酶具有很好的耐碱性;金属离子对该酶催化活性没有明显的激活作用,表明该甲壳素酶是非金属酶.同时,对该酶的底物特异性进行研究,发现该酶对胶体甲壳素和甲壳素水解能力较强,对淀粉和纤维素无水解能力,对不同脱乙酰度的壳聚糖的水解程度随脱乙酰度不同而变化,表明该酶只能特异性识别并降解GlcNAc-GlcNAc之间的糖苷键;以胶体甲壳素为底物时,米氏常数Km为4.41 mg/mL,最大反应初速度为1.08 mg/min.利用薄板层析和高效液相色谱对酶解产物进行分析,结果表明该甲壳素酶对胶体甲壳素的降解产物主要是(GlcNAc)2.综上所述,本研究所涉甲壳素酶在甲壳二糖的酶法制备方面具有较好的应用前景.