Two-dimensional counter-current chromatography for the preparative separation of prenylflavonoids from Artocarpus altilis

Less Configuration and More Dimensionality: Preparative Heart-Cut Multidimensional Liquid Chromatography Based on Trapping Arrays

The resolving power of multiple dimensional liquid chromatography (mD-LC) is multiplicative as it adds dimensions. However, the issue in creating a preparative mD-LC system is that the higher the dimensionality, the more complicated the system configuration. Thus, we presented a new configuration of preparative mD-LC using one set of LC modules and trapping array-based multiple heart-cut interfaces. A preparative two-dimensional liquid chromatography (2D-LC) separation of herbal medicine formulation produced 40 compounds with a purity of >90%. During the separation process, the interface stores the fractions and allocates positions for the fractions from a different dimension; LC draws the fraction from the interface, makes ⁿD separation, and sends isolated fractions to the interface. By repeating this process, we achieved variable dimensionality of LC separations. We also presented a preparative 3D-LC separation of herbal medicines to validate the principle of "less configuration and more dimensionality". Thus, we can explore the higher dimensional preparative separations. The developed preparative mD-LC displayed exceptional power in the isolation of various compounds and has great potential in the application of natural products.

High-Speed Counter-Current Chromatography with an Online Storage Technique for the Preparative Isolation and Purification of Dihydroflavonoids from Sophora alopecuroides L

INTRODUCTION

High-speed counter-current chromatography (HSCCC) is an efficient and non-absorption separation technique, but limitations still exist in simultaneous isolation of complex structures of natural products. Moreover, particular methods are various for different kinds of natural products.

OBJECTIVE

A novel HSCCC strategy combined with an online storage recycling elution (OSR-CCC) technique was developed for the quick separation of naturally occurring dihydroflavonoids from the extract of the herb Sophora alopecuroides L.

METHODOLOGY

In the separation procedure, a storage loop and two six-port valves were connected to a HSCCC system. Effluent A was subjected to an online storage loop and then to recycling separation three times after effluent B was collected in head-to-tail mode. After completion of the recycling separation of effluent A, the elution was switched to tail-to-head mode to collect effluent C. A biphasic solvent system of n-hexane/ethyl acetate/methanol/water (9:6:6:8, v/v/v/v) was used as the separation solvent during the whole elution.

RESULTS

Six constituents were isolated simultaneously from the extract (200 mg) of S. alopecuroides by running HSCCC non-stop, and their purities were higher than 95.0%. Their structures were determined as the pterocarpan glycoside sophoratonkin (1) (10.0 mg) and five dihydroflavonoids, alopecurone F (2) (5.4 mg), lehmannin (3) (11.0 mg), alopecurone A (4) (35.0 mg), sophoraflavanone G (5) (21.0 mg), alopecurone B (6) (31.0 mg).

CONCLUSION

This recycling HSCCC method combined with an online storage technique could be a rapid, effective and simple approach to isolate stilbene-dihydroflavonoids from herbs of the Sophora genus simultaneously. Copyright © 2017 John Wiley & Sons, Ltd.

At-line hyphenation of high-speed countercurrent chromatography with Sephadex LH-20 column chromatography for bioassay-guided separation of antioxidants from vine tea (Ampelopsis grossedentata)

Vine tea (Ampelopsis grossedentata), a widely used healthy tea, beverage and herbal medicine, exhibited strong antioxidant activity. However, systematic purification of antioxidants, especially for those with similar structures or polarities, is a challenging work. Here, we present a novel at-line hyphenation of high-speed countercurrent chromatography with Sephadex LH-20 column chromatography (HSCCC-Sephadex LH-20 CC) for rapid and efficient separation of antioxidants from vine tea target-guided by 1,1-diphenyl-2-picryl-hydrazyl radical-high performance liquid chromatography (DPPH-HPLC) experiment. A makeup pump, a six-port switching valve and a trapping column were served as interface. The configuration had no operational time and mobile phase limitations between two dimensional chromatography and showed great flexibility without tedious sample-handling procedure. Seven targeted antioxidants were firstly separated by stepwise HSCCC using petroleum ether-ethyl acetate-methanol-water (4:9:4:9, v/v/v/v) and (4:9:5:8, v/v/v/v) as solvent systems, and then co-eluted antioxidants were on-line trapped, concentrated and desorbed to Sephadex LH-20 column for further off-line purification by methanol. It is noted that six elucidated antioxidants with purity over 95% exhibited stronger activity than ascorbic acid (VC). More importantly, this at-line hyphenated strategy could sever as a rapid and efficient pathway for systematic purification of bioactive components from complex matrix.

One-step separation of nine structural analogues from Poria cocos (Schw.) Wolf. via tandem high-speed counter-current chromatography

A novel one-step separation strategy-tandem high-speed counter-current chromatography (HSCCC) was developed with a six-port valve serving as the switch interface. Nine structural analogues including three isomers were successfully isolated from Poria cocos (Schw.) Wolf. by one step. Compared with conventional HSCCC, peak resolution of target compounds was effectively improved in tandem one. Purities of isolated compounds were all over 90% as determined by HPLC. Their structures were then identified via UV, MS and (1)H NMR, and eventually assigned as poricoic acid B (1), poricoic acid A (2), 3β,16α-dihydroxylanosta-7, 9(11), 24-trien-21-oic acid (3), dehydrotumulosic acid (4), polyporenic acid C (5), 3-epi-dehydrotumulosic acid (6), 3-o-acetyl-16α-hydroxydehydrotrametenolic acid (7), dehydropachymic acid (8) and dehydrotrametenolic acid (9) respectively. The results indicated that tandem HSCCC can effectively improve peak resolution of target compounds, and can be a good candidate for HSCCC separation of structural analogues.

Safety Evaluation of Artocarpus altilis as Pharmaceutical Agent in Wistar Rats

This study was designed to elucidate the acute toxicity of Artocarpus altilis leaf and bark extracts. In acute toxicity study, no mortality or any toxic reaction was recorded in any group after 14 days of administering the extracts (2000 mg Kg⁻¹ BW). The extracts (ALA, ABA, ALM, and ABM) did not cause any behavioural or physical changes in experimental rats. There was no significant (P ≤ 0.05) difference in the biochemical parameters analysed between the groups. Slight elevation in activities of AST and ALT in extract treated groups was observed, but this did not exert any deleterious effect on the normal metabolism which was supported by the histopathology of liver. Histopathological studies showed no remarkable changes after 14 days of oral administration of ALA, ABA, ALM, and ABM extracts. The study contributes to establishing the nontoxic quality parameters of Artocarpus altilis leaf and bark parts and the results suggest the safety of the extracts in therapeutic uses.

Development of a method to extract and purify target compounds from medicinal plants in a single step: online hyphenation of expanded bed adsorption chromatography and countercurrent chromatography

Pure compounds extracted and purified from natural sources are crucial to lead discovery and drug screening. This study presents a novel two-dimensional hyphenation of expanded bed adsorption chromatography (EBAC) and high-speed countercurrent chromatography (HSCCC) for extraction and purification of target compounds from medicinal plants in a single step. The EBAC and HSCCC were hyphenated via a six-port injection valve as an interface. Fractionation of ingredients of Salvia miltiorrhiza and Rhizoma coptidis was performed on the hyphenated system to verify its efficacy. Two compounds were harvested from Salvia miltiorrhiza, one was 52.9 mg of salvianolic acid B with an over 95% purity and the other was 2.1 mg of rosmarinic acid with a 74% purity. Another two components were purified from Rhizoma coptidis, one was 4.6 mg of coptisine with a 98% purity and one was 4.1 mg of berberine with a 82% purity. The processing time was nearly 50% that of the multistep method. The results indicate that the present method is a rapid and green way to harvest targets from medicinal plants in a single step.

Modeling gradient elution in countercurrent chromatography: efficient separation of tanshinones from Salvia miltiorrhiza Bunge

Countercurrent chromatography (CCC) is a support-free liquid-liquid chromatography using centrifugal fields to hold the liquid stationary phase. CCC has been widely applied in the separation of various natural and synthetic components using a variety of biphasic liquid systems. The related hexane or heptane/ethyl acetate/methanol or ethanol/water biphasic liquid systems demonstrated their significance in CCC. Gradient is difficult in CCC since any composition change in one phase induces a composition change of the other phase to maintain phase equilibrium. This work provides a new insight into linear gradient elution in CCC that is feasible with some biphasic liquid systems such as selected compositions of the hexane/ethyl acetate/ethanol/water systems. The equations modeling solute motion inside the CCC column are proposed. Particular compositions of the liquid system, namely the hexane/ethyl acetate/ethanol/water 8:2:E:W compositions with E + W = 10, were studied from W = 1 to 9. They showed moderate changes in the upper organic phase compositions. The model is tested with the separation of tanshinones from the rhizome of Salvia miltiorrhiza Bunge. Different linear solvent gradient profiles were experimentally performed between 8:2:5:5 and 8:2:3:7 compositions and the results were evaluated using the proposed model. Five tanshinones including dihydrotanshinone I, cryptotanshinone, tanshinone I, 1,2-dihydrotanshinquinone, and tanshinone IIA have been successfully separated (>95% purities) using a gradient profile optimized by the developed model. The gradient model can be used only with biphasic liquid systems in which one phase shows minimum composition changes when the other phase composition changes notably. This case is not the general case for biphasic liquid systems but can be applied with specific compositions of the quaternary hexane or heptane/ethyl acetate/methanol or ethanol/water most useful CCC liquid systems.

Design of countercurrent separation of Ginkgo biloba terpene lactones by nuclear magnetic resonance

Terpene lactones such as bilobalide, ginkgolides A, B, C, and J are major bioactive compounds of Ginkgo biloba L. Purification of these compounds is tedious due to their similar chemical properties. For the purpose of developing an effective and efficient method for both analytical and preparative separation of terpene lactones in G. biloba, an innovative orthogonality-enhanced high-speed countercurrent chromatography (HSCCC) method was established. Taking advantage of quantitative (1)H NMR (qHNMR) methodology, partition coefficients (K) of individual terpene lactones were calculated directly from crude G. biloba leaf extract, using their H-12 signals as distinguishing feature. The partitioning experiment assisted the design of a two dimensional (2D) HSCCC procedure using a pair of orthogonal HSCCC solvent systems (SSs), ChMWat +4 and HEMSoWat +3/0.05%. It was surprising that the resolution of ginkgolides A and B was improved by 25% in the HEMWat +3 SS modified with 0.5% DMSO. Consequently, all five terpene lactones could be well separated with qHNMR purity>95% from G. biloba leaf extract. The separation was further evaluated by offline qHNMR analysis of HSCCC fractions associated with Gaussian curve fitting. The results showed less than 2% error in HSCCC retention predicted from the partitioning experiment. This compelling consistency demonstrates that qHNMR-derived K determination ("K-by-NMR") can be used to predict CCC fractionation and target purification of analytes from complex mixtures. Furthermore, Gaussian curve fitting enabled an accurate prediction of less than 2% impurity in the CCC fraction, which demonstrates its potential as a powerful tool to study the presence of minor constituents, especially when they are beyond the detection limit of conventional spectroscopic detectors.

Developments of instruments and methods related with high-speed countercurrent chromatography and their applications in research of natural medicines

High-speed countercurrent chromatography (HSCCC) is a liquid-liquid separation chromatographic technique which uses no solid supporting medium. During its rapid development in the last 30 years, great progress has been made in the instrumentation, the basic study and application of HSCCC. It has significant advantages over other instrumental separation techniques, in its high efficiency and continuous processing capability. In recent years, HSCCC has been widely used in research and development of natural medicines and functional foods, including preparative separation, fingerprint analysis and screening of bioactive constituents. A review of the technique is presented in this paper.

On-line coupling of counter-current chromatography and macroporous resin chromatography for continuous isolation of arctiin from the fruit of Arctium lappa L

In this work, we have developed a novel hybrid two-dimensional counter-current chromatography and liquid chromatography (2D CCC x LC) system for the continuous purification of arctiin from crude extract of Arctium lappa. The first dimensional CCC column has been designed to fractionalize crude complex extract into pure arctiin effluent using a one-component organic/salt-containing system, and the second dimensional LC column has been packed with macroporous resin for on-line adsorption, desalination and desorption of arctiin which was effluent purified from the first CCC dimension. Thus, the crude arctiin mixture has been purified efficiently and conveniently by on-line CCC x LC in spite of the use of a salt-containing solvent system in CCC separation. As a result, high purity (more than 97%) of arctiin has been isolated by repeated injections both using the ethyl acetate-8% sodium chloride aqueous solution and butanol-1% sodium chloride aqueous solution. By contrast with the traditional CCC processes using multi-component organic/aqueous solvent systems, the present on-line CCC x LC process only used a one-component organic solvent and thus the solvent is easier to recover and regenerate. All of used solvents such as ethyl acetate, n-butanol and NaCl aqueous solution are low toxicity and environment-friendly. Moreover, the lower phase of salt-containing aqueous solution used as mobile phase, only contained minor organic solvent, which will save much organic solvent in continuous separation. In summary, our results indicated that the on-line hybrid 2D CCC x LC system using one-component organic/salt-containing aqueous solution is very promising and powerful tool for high-throughput purification of arctiin from fruits of A. lappa.

Strategies of solvent system selection for the isolation of flavonoids by countercurrent chromatography

Flavonoids form a large class of important naturally occurring bioactive compounds. Their isolation and purification from natural sources can sometimes be very difficult and time-consuming when traditional phytochemical techniques are used. Countercurrent chromatography (CCC), a support-free liquid-liquid partition chromatography technique, is very useful for the isolation of polar compounds and its use is increasing in the natural products field. In this paper, we propose strategies of solvent system selection for the isolation of flavonoids by CCC, based on data from the literature, plus incorporation of own practical experiences. The selected references report the isolation of over 300 different flavonoid compounds from more than 100 plant species, using 40 different solvent systems, showing the versatility of this technique. The solvent system hexane-ethylacetate-methanol-water is proposed as a starting point for the separation of samples containing free flavonoids, as it was cited in more than 60% of the papers. A "fine tuning" step is proposed at each level of this solvent family. Other modifications include exchanging the alcohol in the system as well as introducing a fifth solvent. The solvent system ethyl-acetate-butanol-water is proposed as the starting point for glycosylated flavonoids. Other solvent systems are also discussed. The use of gradients is proposed for samples containing both free and glycosylated flavonoids, as the polarity window is larger in these cases. High-speed countercurrent chromatography was used in 89% of the reviewed data.

Countercurrent chromatography: people and applications

The scientific literature was scanned for the published research articles dealing with countercurrent chromatography (CCC) over the time period 1980-May 2008. The search returned 1638 articles that were analyzed focussing on people and applications. Concerning the people, it was found that the geographical location of the CCC authors was relatively well balanced between USA, Asia with mainly China and Japan and Europe. Yoichiro Ito, the inventor of the technique, is by far the most productive author in the field with 331 articles or more than one over five CCC articles published in the time period. Without surprise, English is the dominant language with more than 82% of the articles. A significant 8% amount of CCC articles were published in Chinese in Chinese journals. Chromatography journals are the logical tribune for half of the published CCC articles. Concerning the applications, the separation and purification of natural compounds is the dominant theme in CCC making the subject of more than one article over two. Starting from the plant extract, CCC in few steps can produce significant amounts of more than 95% pure compounds used for identification and/or property studies. Other applications are found in the pharmaceutical and chemical field. The separation of enantiomers on the preparative scale is a field of growing importance.

Countercurrent separation of natural products

An assessment of the technology and method development in countercurrent chromatography (CCC) and centrifugal partition chromatography (CPC), collectively referred to as countercurrent separation (CS), is provided. More than six decades of CS theory and applications are critically reviewed and developed into a practical guide to CS for natural products research. The necessary theoretical foundation is given for better use of CS in the separation of biological molecules of any size, small to large, and from any matrix, simple to complex. The three operational fundamentals of CS--instrumentation, biphasic solvent systems, and theory--are covered in a prismatic fashion. The goal of this review is to provide the necessary background and references for an up-to-date perspective of CS and to point out its potential for the natural products scientist for applications in natural products chemistry, metabolome, and proteome research involving organisms from terrestrial and marine sources.

Natural product isolation

Since the 1990s, interest in natural product research has increased considerably. Following several outstanding developments in the areas of separation methods, spectroscopic techniques, and sensitive bioassays, natural product research has gained new attention for providing novel chemical entities. This updated review deals with sample preparation and purification, recent extraction techniques used for natural product separation, liquid-solid and liquid-liquid isolation techniques, as well as multi-step chromatographic operations. It covers examples of papers published since the NPR review 'Modern separation methods' by Marston and Hostettmann,1 with major emphasis on methods developed and the research undertaken since 2000.