A consecutive preparation method based upon accelerated solvent extraction and high-speed counter-current chromatography for isolation of aesculin from Cortex fraxinus

Nuclear magnetic resonance-based solvent system selection for counter-current chromatography separation of compounds present in the same high-performance liquid chromatography peak: Flavonoids in barley seedlings as an example

Partition coefficient is a key parameter for counter-current chromatography separation. High-performance liquid chromatography (HPLC) is the most commonly used tool for the screening of partition coefficients. However, HPLC technology is not applicable to the compounds present in the same chromatographic peak. Nuclear magnetic resonance (NMR) technology could easily distinguish compounds according to their characteristic absorption even if they exist in the same HPLC peak. In this study, two flavonoids present in the same HPLC peak were successfully purified by counter-current chromatography with a solvent system screened by NMR to show the great potential of NMR technology in the screening of the partition coefficient of co-efflux compounds. Through NMR screening, an optimized ethyl acetate/n-buthanol/water (7:3:10, v/v/v) system was applied in this study. As a result, two flavonoids, including 4.8 mg of 3'-methoxyl-6'''-O-feruloylsaponarin and 9.8 mg of 6'''-O-feruloylsaponarin were separated from 15 mg of the mixture. There is only one methoxy group difference between the two flavonoids. This study provides a new strategy for the screening of counter-current chromatography solvent systems and broadens the application scope of counter-current chromatography.

Preparation of 5-hydroxymethylfurfural from Schisandra chinensis (Turcz.) Baill by high-speed counter-current chromatography: Comparison of conventional and consecutive separation

Schisandra chinensis is a kind of plant with high medicinal value, which contains many medicinal ingredients, including 5-hydroxymethylfurfural. In the present study, an efficient method based on high-speed counter-current chromatography was established for the preparation of 5-hydroxymethylfurfural from Schisandra chinensis. Petroleum ether-ethyl acetate-methanol-water (2:5:2:5, v/v) was selected as the solvent system for high-speed counter-current chromatography. In order to improve the yield of single separation, the sample size was continuously optimized and improved. The result showed that 1250 mg was the most suitable sample size, and 41 mg of the target compound with 97% purity was obtained by a single run. To further improve the yield, consecutive high-speed counter-current chromatography was introduced and compared with the results of high-speed counter-current chromatography single run. The results showed that although the purity was reduced to 92%, 430 mg of the target compound was obtained from 12.5 g of ethanol extract within 670 min after 10 consecutive injections. It indicated that consecutive separation not only increased the yield of the target compound, but also saved the separation time and greatly improved the separation efficiency of high-speed counter-current chromatography.

A simple and highly efficient counter-current chromatography method for the isolation of concentrated fractions of compounds based on the sequential sample loading technique: Comparative theoretical study of conventional multiple and intermittent sample loading counter-current chromatography separations

A new modification of the conventional multiple sample loading (MSL) mode - sequential sample loading (SSL) - is suggested to enhance further the performance of the counter-current chromatography (CCC) separation processes. The sequential sample loading technique is simple and easy to implement: the continuous sample solution supply to a CCC column is alternated (interrupted) with short periods of the "pure" mobile phase supply. Periodic (batch) and continuous SSL CCC separations can be designed and implemented. In continuous processes, the sample solution loading is carried out in the form of separate series, consisting of a number of sequential sample solution loads. In this work, the modeling of the conventional multiple sample loading and the sequential sample loading counter-current chromatography is used to compare the two operating modes considered. Equations for the calculation of band profiles, the recovery yield and the purity are given. Equations are also derived permitting the calculation of the optimum operating parameters of the separation processes. It is shown that the use of sequential sample loading makes it possible to produce fractions of purified compounds with a much higher concentration than in the original sample solution. The simulations of the conventional multiple sample loading and the sequential sample loading counter-current chromatography separations are presented in "Mathcad" software.

Operating mode and parameter selection in liquid-liquid chromatography

The presence of a liquid stationary phase in liquid-liquid chromatography (LLC) allows for high versatility of operation as well as adaptability to different sample types and separation tasks. LLC, also known as countercurrent chromatography (CCC) or centrifugal partition chromatography (CPC), offers the user a variety of operating modes, many of which have no direct equivalent in conventional preparative liquid-solid chromatography. These operating modes have the potential to greatly improve LLC separation performance compared to the standard "classical" isocratic batch injection mode, and they often require minimal to no addition of equipment to the standard set-up. However, reports of the use of alternative LLC operating modes make up only a fraction of the literature. This is likely due, at least in part, to the lack of clear guidelines and methods for operating mode and parameter selection, leaving alternative process options to be avoided and underutilized. This review seeks to remedy this by providing a thorough overview of the available LLC operating modes, identifying the key characteristics, advantages and disadvantages, and areas of application of each. Additionally, the equations and short-cut models aiding in operating mode and parameter selection are presented and critiqued, and their notation is unified for clarity. By rendering LLC and its alternative operating modes more accessible to current and prospective users, it is hoped to help expand the application of this technology and support the achievement of its full potential.

Efficient Protocol for Isolation of Rhaponticin and Rhapontigenin with Consecutive Sample Injection from Fenugreek (Trigonella foenum-graecum L.) by HSCCC

High efficiency and less solvent consumption are the essential requirements of high-speed countercurrent chromatography (HSCCC), especially for the large-scale preparation. In this study, an efficient HSCCC strategy with consecutive sample injection was successfully developed to rapidly separate and purify rhaponticin and rhapontigenin from the seeds of the Chinese medicinal herb fenugreek (Trigonella foenum-graecum L.). The effective separation was achieved using n-hexane-ethyl acetate-methanol-water (1:4:2:6, v/v/v/v) as the two-phase solvent system, in which the mobile phase was eluted at an optimized flow rate of 2.2 mL/min and a revolution speed of 850 rpm. After consecutively loading four identical fenugreek samples, each containing 120 mg, HSCCC separation yielded 146.4 mg of rhaponticin and 174.8 mg of rhapontigenin with purities of 98.6 and 99.1%, respectively, as determined by high-performance liquid chromatography at 320 nm. Their chemical structures were identified using UV spectroscopy, (1)H-NMR and (13)C-NMR. The HSCCC method with consecutive sample injection allowed faster separation and produced less solvent waste, suggesting that it is an efficient way to rapidly separate and purify natural products on a large scale.

Liquid chromatography tandem mass spectrometry in study of the pharmacokinetics of six steroidal saponins in rats

A rapid, simple and sensitive high-performance liquid chromatography tandem mass spectrometry method was developed and validated for simultaneous determination of six main steroidal saponins in Paris polyphylla in rat plasma. Ginsenoside Rg3 was selected as the internal standard (IS). Plasma samples were pretreated with protein precipitation, and the separation was achieved on a reverse phase Agilent poroshell120 EC-C18 column using a gradient mobile phase system of acetonitrile-water containing 0.1% formic acid. The triple quadruple mass spectrometer was set in negative electrospray ionization mode and multiple reaction monitoring (MRM) was used for six steroidal saponins quantification. The precursors to produce ion transitions monitored for polyphyllin I, polyphyllin II, polyphyllin VI, polyphyllin VII, dioscin, gracillin and IS were m/z 899.5>853.4, 1059.5>1013.5, 783.4>737.4, 1075.5>1029.5, 913.5>867.4, 929.5>883.4 and 819.5>783.4, respectively. The intra- and inter-day precisions (RSD%) were less than 13% and the average extraction recoveries ranged from 85% to 97.0% for each analyte. Six steroidal saponins were proved to be stable during sample storage, preparation and analytical procedures. The established method was employed for simultaneous quantification and successfully used for the first time for the pharmacokinetics evaluation of the six main compounds after intragastric administration of P. polyphylla extract in Sprague-Dawley rats.