Recovery and recycling of solvent of counter-current chromatography: The sample of isolation of zeaxanthin in the Lycium barbarum L. fruits.

An efficient method of recovering and recycling solvent for counter-current chromatography was established by which zeaxanthin was separated from Lycium barbarum L. fruits. A column with activated carbon combined with high performance counter-current chromatography formed the recovering and recycling solvent system. Using the solvent system of n-hexane-ethyl acetate-ethanol-water (8:2:7:3, v/v) from the references, five injections were performed with an almost unchanged purity of zeaxanthin (80.9, 81.2, 81.5, 81.3, and 80.2% respectively) in counter-current chromatography separation. Meanwhile, the mobile phase reduced by half than conventional counter-current chromatography. By this present method, an effective improvement of counter-current chromatography solvent utilization was achieved.

Chiral counter-current chromatography: A survey of its instrument, mechanism, procedure, and applications.

The chiral separation by counter-current chromatography has made great progress in the past three decades. It has become increasingly popular in the field of chiral separation, and many applications have been introduced during the last years. This review mainly focuses on the current topics, applications, and trends in chiral separation by counter-current chromatography. It contains the development of modern counter-current chromatography apparatus, theory of counter-current chromatography, overview of applications of chiral counter-current chromatography enantioseparation, its current situation, and challenges. At last, some conclusions and perspectives also have been discussed in this review.

Full use of the liquid nature of the stationary phase: The development of elution-extrusion counter current chromatography.

Elution-extrusion counter current chromatography extrudes the most solute retained in the column with the highest possible peak resolution. It can greatly improve the hydrophobic window. In recent years, elution-extrusion counter current chromatography has received extensive attention in the separation of complex samples. This article first reviews the development and application of elution-extrusion counter current chromatography, including its origin, mechanism, advantages and disadvantages, and some representative applications. At the same time, this review also shared our visions and ideas on how to improve the elution-extrusion mode. This article aims to provide certain reference for the research of this technology.

The applicability of high-speed counter current chromatography to the separation of natural antioxidants.

Antioxidants play an essential role in human health, as they have been found to be capable of lowering the incidence of many diseases, such as cancer and angiocardiopathy. Currently, more attention is paid to natural antioxidants because of the possible insecurity of synthetic antioxidants. Thus, the development of efficient techniques or methods to separate antioxidants from natural sources is requested urgently. High-speed counter current chromatography (HSCCC) is a unique support-free liquid-liquid chromatographic technique and has been widely applied in the field of separation of natural products. In this review, we summarize and analyze the related researches on the application of HSCCC in the separation of various natural antioxidants so far. The purpose of the article is to provide a certain theoretical support for the separation of natural antioxidants by HSCCC, and to make full use of advantages of HSCCC in the separation of bioactive components. In particular, some key problems associated with the separation strategies, the structural categories of natural antioxidants, solvent system choices, and the application of different elution modes in HSCCC separation, are summarized and commented. We expect that the content reviewed can offer more evidence for the development of the field of natural antioxidants separation, so as to achieve large-scale preparation of natural antioxidants.

Effective on-line high-speed shear dispersing emulsifier technique coupled with high-performance countercurrent chromatography method for simultaneous extraction and isolation of carotenoids from Lycium barbarum L. fruits.

An efficient combination strategy based on high-speed shear dispersing emulsifier technique and high-performance countercurrent chromatography was developed for on-line extraction and isolation of carotenoids from the fruits of Lycium barbarum. In this work, the high-speed shear dispersing emulsifier technique has been employed to extract crude extracts using the upper phase of high-performance countercurrent chromatography solvent system composed of n-hexane-dichloromethane-acetonitrile (10:4:6.5, v/v) as the extraction solvent. At the separation stage, the high-performance counter-current chromatography process adopts elution-extrusion mode and the upper phase of the solvent system as stationary phase (reverse-phase mode). As a result, three compounds including zeaxanthin, zeaxanthin monopalmitate, and zeaxanthin dipalmitate with purities of 89, 90, and 93% were successfully obtained in one extraction-separation operation within 120 min. The targeted compounds were analyzed and identified by high-performance liquid chromatography, mass spectrometry, and NMR spectroscopy. The results indicated that the present on-line combination method could serve as a simple, rapid, and effective way to achieve weak polar and unstable compounds from natural products.

Counter-current chromatography melamine-modified column and its separation mechanism.

In this work, to further verify and develop the novel counter-current chromatography modified column separate mode, a melamine modified counter-current chromatography column was prepared. Meanwhile, the modified counter-current chromatography column was used to separate stevioside and rebaudioside A with the same partition coefficient in chosen solvent system to evaluate its separation efficiency. The results show that because of the presence of intermolecular forces between melamine and model compounds, better separation could be achieved on the modified column while it's almost impossible to be separated on the unmodified column. So the results of this research further show that column modified method is a possible approach to further increase the separation ability of counter-current chromatography. Take advantage of large sample handing capacity of counter-current chromatography, the mothed may have great potential to be an efficient method of separation and preparation enantiomer compounds.

A simple gradient equilibrium method for better separation in countercurrent chromatography.

The stationary phase retention is one of the most important parameters in countercurrent chromatography. In this work, a simple gradient equilibrium method was developed to further improve the stationary phase retention based on the optimized condition in the traditional equilibrium model. Meanwhile, this novel gradient equilibrium method was used to separate three flavone model compounds and compared with the conventional isocratic equilibrium method to evaluate the separation efficiency. The results show that better resolution or shorter separation time could be achieved with gradient equilibrium compared to isocratic equilibrium. So this novel equilibrium method has enormous potential for obtaining a better separation or saving the separating time in the preparative separation of target compounds.

Surface modification of polytetrafluoroethylene column for two-stationary phase separations by counter-current chromatography.

To improve the separation capability of CCC, a novel solid-liquid two-stationary phases CCC (ASP-CCC) column was prepared employing graphene oxide (GO) conjugated poly-dopamine (PD) coating (GO/PD) as auxiliary stationary phase (ASP). The results of Scanning electron microscopy (SEM), contact angle and X-ray photoelectron spectroscopy (XPS) indicated that nanostructured GO and PD were successfully grafted on the inner wall of the PTFE column. Three alkaloid compounds were selected as the target analytes to evaluate the performance of the novel column. Because of the intermolecular force (hydrogen bond, electrostatic interaction and π-π interaction) between the ASP and model compounds, three analytes were well separated with this novel ASP-CCC column. Additionally, the novel column exhibited higher stationary phase retention ratio, about 8%, than original column without changing the chromatographic condition. Furthermore, the eluotropic sequence of analytes on novel column was in accordance with that in the original column. This suggested that the novel column is a CCC column with auxiliary stationary phase (ASP) in its own right, and the present separation mode is the combination of partition chromatography and adsorption chromatography.

[Chemical constituents of Tamarix chinensis].

OBJECTIVE: To study the chemical consistuents of Tamarix chinensis. METHODS: The compounds were isolated and purified by column chromatography and their structures were elucidated through spectroscopic analysis. RESULTS: Nine compounds were isolated and identified as isotamarixen(1), matairesinol(2), tetepathine(3), kaempferol(4), 4'-methylkaempferol(5),4',7-dimethylkaempferol (6), hexacosyl-3-caffeate(7), ferulic acid(8) and 3-methoxyl methyl gallate(9). CONCLUSION: Compounds 1-3,7 and 8 are isolated from this plant for the first time, compounds 1-3,7 are isolated from Tamarix genus for the first time.

[Studies on the chemical constituents from flower of Paulownia fortunei].

OBJECTIVE: To study the chemical constituents of the flower of Paulownia fortunei. METHODS: The constituents were isolated by column chromatography and their structures were elucidated through spectroscopic analysis. RESULTS: The compounds were identified as: apigenin (I), luteolin (II), Hesperetin (III), Naringenin-7-O-beta-D-glucoside (IV), Arbutin (V), 4-hydroxybenzyl-beta-D-glucoside (VI), abscisic acid (VII) and 1-acetoxy-3-hydroxypropan-2-yl-3-hydroxypentanoate (VIII). CONCLUSION: All these compounds are obtained from the flower of this plant for the first time.

[Chemical constituents from the flower of Paulownia fortunei( seem. ) Hemsl].

OBJECTIVE: To study the chemical constituents of the flower of Paulownia fortunei (Seem.) Hemsl. METHODS: The constituents were isolated by column chromatography and their structures were elucidated through spectroscopic analysis. RESULTS: The compounds were identified as diplacone( I ) ,3 '-O-methyldiplacone ( II ) , mimulone ( ll) , ursolic acid( IV ), beta-sitosterol ( V ), daucosterol ( VI). CONCLUSION: All these compounds were obtained from the flower for the first time.