High-speed countercurrent chromatography

Development of a strategy for a quick process for separation of volatile compounds in counter-current chromatography: purification of cinnamaldehyde from Cinnamomum cassia by high performance counter-current chromatography

It is a challenge for many researchers to separate volatile compounds. In this study, we introduce a rapid and efficient method of separating target compound from the twigs of Cinnamomum cassia by high performance counter-current chromatography. Under the bioassay guidance, the total extract exhibited a potential activity against NO production in RAW 264.7 macrophages and the total extract was further separated by high performance counter-current chromatography. Cinnamaldehyde (1) was enriched by counter-current chromatography (CCC) with reversed-phase mode using n-hexane-ethyl acetate-methanol-water (1:1:1:1,v/v/v/v) as the solvent system. Further identification was achieved by high performance liquid chromatography (HPLC).

Development of a novel cross-axis countercurrent chromatographic instrument with six separation columns: Design, dynamics, optimization, prototyping, and experiment

This paper presents the development of a novel cross-axis countercurrent chromatographic instrument (CCCI) with six separation columns, including design, dynamics, optimization, prototype construction, and experimental validation. The conceptual design and the structural design of the cross-axis CCCI are performed while considering the requirements for the separation operation and design. The dynamic analysis is carried out in order to guarantee the local balance and the global balance for the CCCI. The relationship between the mechanical structure parameters and partition efficiency is investigated by analyzing the effect of mechanical structure parameters on the centrifugal force field. By virtue of the modal analysis of the mechanical structure, the critical speed and the weak link of the CCCI are achieved. Aiming at the problem of the weak link, the structural optimization is done. The presented CCCI has six separation columns distributed around the central revolution axis, and it has more separation columns than that of the existing chromatographic instrument. The CCCI has an axial symmetry structure in the three-dimensional space. Thus it can have better dynamics stability than the CCCI having less separation columns with a symmetry structure in the plane. A physical prototype is built, and then the partition efficiency and its effect factors are tested by the single experimental variable method. The results show that the CCCI runs smoothly and has a good retention rate of stationary phase. It is also proved that the developed CCCI has a good partition efficiency on bovine serum albumin and lysozyme.

Ionic Liquid-Liquid Chromatography: A New General Purpose Separation Methodology

Ionic liquids can form biphasic solvent systems with many organic solvents and water, and these solvent systems can be used in liquid-liquid separations and countercurrent chromatography. The wide range of ionic liquids that can by synthesised, with specifically tailored properties, represents a new philosophy for the separation of organic, inorganic and bio-based materials. A customised countercurrent chromatograph has been designed and constructed specifically to allow the more viscous character of ionic liquid-based solvent systems to be used in a wide variety of separations (including transition metal salts, arenes, alkenes, alkanes, bio-oils and sugars).

Novel Designs for Centrifugal Countercurrent chromatography: V. Comparative Studies on Performance of Various Column Configurations

The conventional toroidal coil in centrifugal countercurrent chromatography has a low level of stationary phase retention, since a half of each helical turn is entirely occupied by the mobile phase. In order to cope with this problem, several new column designs including zigzag, saw-tooth and figure-8 patterns have been introduced and their performance was compared in terms of retention of the stationary phase (Sf), peak resolution (Rs), theoretical plate number (N) and column pressures. Overall results of experiments indicate that the figure-8 column yields the highest Rs when the lower phase is used as the mobile phase. Since the column pressure of all these new columns are much lower than that in the traditional toroidal coil column, the separation efficiency can be improved using a long separation column without a risk of column damage by high back pressure.

Novel Design for Centrifugal Countercurrent Chromatography: II. Studies on Novel Geometries of Zigzag Toroidal Tubing

The toroidal column using a zigzag pattern has been improved in both retention of the stationary phase and peak resolution. To further improve the retention of stationary phase and peak resolution, a series of novel geometric designs of tubing (plain, mid-clamping, flattened and flat-twisted tubing) was evaluated their performance in CCC. The results showed that the tubing which was flattened vertically against centrifugal force (vert-flattened tubing) produced the best peak resolution among them. Using vert-flattened tubing a series of experiments was performed to study the effects of column capacity and sample size. The results indicated that a 0.25 ml capacity column is ideal for analysis of small amount samples.

Novel Design for Centrifugal Counter-Current Chromatography: III. Saw Tooth Column

The toroidal coil using an equilateral triangular core and zigzag pattern column have improved both retention of the stationary phase and peak resolution of the conventional toroidal coil in centrifugal counter-current chromatography. To further improve the retention of stationary phase and peak resolution, a novel saw tooth column was designed and the performance of the system was evaluated at various flow rates. The results indicated that both retention of the stationary phase and peak resolution were improved as the flow rate was decreased and at a flow rate of 0.005 ml/min the resolution is remarkably increased. Modification of the tubing called flat-twisted tubing further improved the peak resolution without increasing the column pressure. With a decreased column length at a capacity of about 0.2 ml, resolution of the saw tooth column was 1.02.

Novel Design for Centrifugal Countercurrent Chromatography: I. Zigzag Toroidal Column

The toroidal coil using an equilateral triangular core has improved both retention of the stationary phase and peak resolution of the conventional toroidal coil in centrifugal countercurrent chromatography. To further improve the retention of stationary phase and peak resolution, a novel zigzag toroidal coil was designed and the performance of the system was evaluated at various flow rates. The results indicated that both retention of stationary phase and peak resolution were improved as the flow rate was decreased. Modification of the tubing by pressing at given intervals with a pair of pliers improved the peak resolution without increasing the column pressure. All these separations were performed under low column pressure indicating the separation can be further improved by increasing the column length and/or revolution speed without damaging the separation column.

PREPARATIVE ISOLATION OF ISORHAMNETIN FROM STIGMA MAYDIS USING HIGH-SPEED COUNTERCURRENT CHROMATOGRAPHY

Preparative high-speed countercurrent chromatography (HSCCC) has been successfully used for the isolation and purification of isorhamnetin from Stigma maydis. This was achieved in two stages: the first separation was performed with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (HEMW) at a volume ratio of 5:5:5:5, yielding isorhamnetinat 65.6 %, which is followed by the second run using a two-phase solvent system composed of HEMW 5:5:6:4, v/v. From 700 mg of the crude extract 11.8 mg of isorhamnetin was obtained at a high purity of 98%. The final identification was performed by MS, (1)H-NMR and (13)C-NMR spectra.

Comparative Study on Separation and Purification of Isoflavones from the Seeds and Sprouts of Chickpea by HSCCC

Chickpea is known as a plant that is rich in protein, carbohydrates, and nutrition, and its seeds and sprouts have been processed into various health foods. In the present study, four isoflavones were purified from the seeds and sprouts of chickpea by high speed countercurrent chromatography (HSCCC) using two biphasic solvent systems composed of n-hexane-ethyl acetate-methanol-water (5:5:5:5, v/v) and ethyl acetate-water (1:1 v/v). The results indicated that 14.2 mg of formononetin, 15.7 mg of biochanin A, 9.1 mg of ononin, 11.3 mg of biochanin A-7-O-β-D-glucoside were obtained from 150 mg of sprout extracts with the purity of 92.26%, 95.86%, 95.32%, and 96.56%, respectively. Compared with the sprouts, separation of seed extracts yielded less amounts of biochanin A-7-O-β-D-glucoside and biochanin A with lower purity. The results indicate that four main isoflavones in chickpea, i.e., isoflavones, formononetin, biochanin A, ononin, and biochanin A-7-O-β-D-glucoside, are substantially increased by biosynthesis during the seed germination.

Spiral Tube Assembly for High-Speed Countercurrent Chromatography: Choice of Elution Modes for Four Typical Two-Phase Solvent Systems

Optimal elution modes were determined for four typical two-phase solvent systems each with different physical parameters to achieve the best peak resolution and retention of the stationary phase by spiral tube high-speed countercurrent chromatography using a suitable set of test samples. Both retention of the stationary phase and partition efficiency are governed by an interplay between two forces, i.e., Archimedean Screw force and radial centrifugal force gradient of the spiral channel. In the polar solvent system represented by 1-butanol./acetic acid/water (4:1:5, v/v/v) with settling time of over 30 s, the effect by the radial centrifugal gradient force dominates giving the best separation of dipeptides either by pumping the lower phase from the inner terminal or the upper phase from the outer terminal of the spiral channel. In the moderately hydrophobic two-phase solvent system represented by hexane/ethyl acetate/methanol/0.1 M HCl (1:1:1:1) with settling time of 19 s, and two hydrophobic solvent systems of hexane/ethanol/water (5:4:1, v/v/v) and non-aqueous binary system of hexane/acetonitrile both having settling time of 9, the effect of the Archimedean screw force play a major role in hydrodynamic equilibrium, giving the best separations by pumping the lower phase from the head or the upper phase from the tail of the spiral channel.

APPLICATION OF PREPARATIVE HIGH-SPEED COUNTERCURRENT CHROMATOGRAPHY FOR SEPARATION OF ELATINE FROM DELPHINIUM SHAWURENSE

Preparative separation of elatine in Delphinium shawurense was achieved for the first time using high-speed countercurrent chromatography (HSCCC). The separation was performed with a solvent system composed of ethyl acetate-chloroform-methanol-water (3:0.1:2:3, v/v) using the lower organic phase as a mobile phase under a revolution speed of 800 rpm. This yielded 72 mg of elatine at over 97% purity with an approximately 95% recovery. The chemical structure was identified by MS and NMR.

Detection of novel secondary metabolites

The study of antibiotics and other fermentation products has shown that a seemingly unlimited number of compounds with diverse structures are produced by microorganisms. The continued high rate of discovery of new chemical entities, in the light of the abundance of microbial products already described, is due to creative screening procedures that incorporate such features as the emphasis on unusual microorgnaisms, their special propagation and fermentation requirements, supersensitive and highly selective assays, genetic engineering both for the biosynthesis of new compounds and in the development of screening systems, early in vivo evaluation, improved isolation techniques, modern procedures for structure determination, computer-assisted identification, and an efficient multidisciplinary approach. This review focuses on the genesis and development of the gamut of methodologies that have led to the successful detection of the wide variety of novel secondary metabolites that include antibacterial, antigungal, antiviral and antitumour antibiotics, enzyme inhibitors, pharmacologically and immunologically active agents, products useful in agriculture and animal husbandry, microbial regulators, and other compounds for which no bioactive role has yet been found.