Preparative Separation and Purification of Kaempferol, Isorhamnetin, and Quercetin by High-Speed Countercurrent Chromatography

Controlled-cycle pulsed liquid-liquid chromatography. A modified version of Craig's counter-current distribution

A new liquid-liquid chromatography technique developed from a combination of controlled-cycle operation and a pulsed-mixing technique is suggested and validated. The controlled-cycle pulsed liquid-liquid chromatography (CPLC) system operates without involving a centrifuge and consists, of a series of multistage units, and a method for imparting pulsation motion to the liquids inside the units (the pulsation cycle). This chromatography technique can be considered as an improved continuous form of Craig's counter-current distribution method, or, alternatively, as a form of droplet chromatography with the cycling mode of operation. The theoretical model has been designed to account for the effects of the basic parameters influencing the CPLC operation. The theoretical model's suitability was proved by direct comparison between the experimental and model responses. The CPLC devices containing 1, 2, 4 and 5 multistage columns (each column was divided into 26 stages) have been designed, fabricated and tested; experiments were conducted to test the chromatographic behavior of organic (monocarboxylic) and mineral acids. The mass transfer rate in the stages depends on the nature of both--phase and sample systems: the highest values were achieved in experiments with acetic acid by using the octane/water biphasic system, where an equilibrium concentration distribution between stationary and mobile phases in the stages was attained. The results obtained demonstrated the potential of the new technique for preparative and industrial scale separations.

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.

Support-free pulsed liquid-liquid chromatography

A simple technique of support-free liquid-liquid chromatography is suggested that operates without incorporation of a centrifuge. The pulsed chromatography apparatus consists of a stationary coiled tube and a pulsation device to produce reciprocating motion of liquid phases within each individual coil segment. This reciprocating motion generates a centrifugal force field varying in intensity and direction that leads to an improved mixing of the two liquid phases and retains the stationary phase in the coiled tubing. The intensity of the back and forth motion of liquid phases within each coil unit can be varied by varying the frequency and/or the amplitude of the pulsations generated by the pulsation device. As the magnitude of the stationary phase retention is of paramount importance for success of the technique, the retention of the stationary phase in the pulsed coil column was experimentally studied. A few experiments were conducted to test the chromatographic behavior of valeric (n-pentanoic) and caproic (n-hexanoic) acids. The results obtained demonstrate the potential of the new separation method for preparative purposes.

Isolation and purification of acteoside and isoacteoside from Plantago psyllium L. by high-speed counter-current chromatography

Two isomeric phenylethanoid glycosides, acteoside and isoacteoside were isolated and purified from the seeds of Plantago psyllium L. for the first time by high-speed counter-current chromatography (HSCCC) using a solvent system consisting of ethyl acetate-water (1:1, v:v). By injecting 200 mg of the n-butanol extract of P. psyllium for five consecutive times, the two-step HSCCC procedure yielded a total of 165 mg of acteoside and 17.5 mg of isoacteoside from 978 mg extract. The recovery rates for acteoside and isoacteoside were 90 and 84%, respectively, and the purities were 98 and 94%, respectively. The HSCCC fractions were analyzed by HPLC and the structures were identified by UV, LC-APCI-MS in negative ion mode, and confirmed by NMR experiments.

Preparative isolation and purification of coumarins from Angelica dahurica (Fisch. ex Hoffm) Benth, et Hook. f (Chinese traditional medicinal herb) by high-speed counter-current chromatography

A preparative high-speed counter-current chromatography (HSCCC) method for isolation and purification of coumarins from Angelica dahurica (Fisch. ex Hoffin) Benth, et Hook. f(Baizhi in Chinese) was successfully established by using n-hexane-methanol-water as the two-phase solvent system in gradient elution mode. The upper phase of n-hexane-methanol-water (5:5:5, v/v) was used as the stationary phase of HSCCC. The mobile phase used in HSCCC was the lower phase of n-hexane-methanol-water (5:5:5, v/v) and n-hexane-methanol-water (5:7:3, v/v) that was changed in gradient. Three major components including imperatorin, isoimperatorin and oxypeucedanine were isolated, each at over 98% purity as determined by high-performance liquid chromatography (HPLC). The peak fractions of HSCCC were identified by 1H-NMR and 13C-NMR.

Preparative isolation and purification of hydroxyanthraquinones and cinnamic acid from the Chinese medicinal herb Rheum officinale Baill. by high-speed counter-current chromatography

A high-speed counter-current chromatography (HSCCC) method for preparative separation and purification of five hydroxyanthraquinones and cinnamic acid from the Chinese medicinal herb Rheum officinale Baill. was developed by using pH-gradient elution. The purities of rhein, emodin, aloe-emodin, chrysophanol, physcion and cinnamic acid were all over 98%, as determined by high performance liquid chromatography (HPLC). The structures of them were identified by 1H NMR.

Application of high-speed counter-current chromatography to the preparative separation and purification of baicalin from the Chinese medicinal plant Scutellaria baicalensis

Baicalin was separated and purified for the first time from the traditional Chinese medicinal plant Scutellaria baicalensis Georgi by high-speed counter-current chromatography. Crude baicalin was obtained by extraction with methanol-water (70:30, v/v) from S. baicalensis Georgi. The separation was performed in two steps with a two-phase solvent system composed of n-butanol-water (1:1, v/v), in which the lower phase was used as the mobile phase at a flow-rate of 1.0 ml min(-1) in the head-to-tail elution mode. A total of 37.0 mg of baicalin at 96.5% purity was yielded from 200 mg of the crude baicalin (containing 21.6% baicalin) with 86.0% recovery as determined by HPLC analysis.

Preparative separation and purification of squalene from the microalga Thraustochytrium ATCC 26185 by high-speed counter-current chromatography

High-speed counter-current chromatography (HSCCC) was successfully applied to the preparative separation and purification of squalene from microalgae. Crude squalene was obtained from the microalga Thraustochytrium ATCC 26185 by extraction with organic solvents. The crude squalene was further separated using a waterless two-phase solvent system composed of n-hexane-methanol (2:1, v/v). The upper phase as the mobile phase was pumped into the column at a flow-rate of 2.0 ml min(-1) in the tail-to-head elution mode. The fractions purified and collected were analyzed by high-performance liquid chromatography. The method yielded 0.2 mg squalene at 96% purity from 150 mg of the crude squalene (0.14% squalene) with 95% recovery. The separation of squalene by HSCCC was completed in 90 min.

Preparative isolation and purification of two isoflavones from Astragalus membranaceus Bge. var. mongholicus (Bge.) Hsiao by high-speed counter-current chromatography

Two isoflavones, calycosin-7-O-beta-D-glycoside and formononetin-7-O-beta-D-glycoside, were separated from n-butanol extract of the root of Astragalus membranaceus Bge. var. mongholicus (Bge.) Hsiao by high-speed counter-current chromatography in two steps using two different solvent systems composed of ethyl acetate-ethanol-n-butanol-water (30:10:6:50, v/v) and ethyl acetate-ethanol-water (5:1:5, v/v). From 200 mg of crude extract, calycosin-7-O-beta-D-glycoside (12 mg) and formononetin-7-O-beta-D-glycoside (10 mg) were isolated at over 95% purity by HPLC analyses, and their structures were identified by MS, 1H NMR and 13C NMR.

Preparative isolation and purification of calycosin from Astragalus membranaceus Bge. var. mongholicus (Bge.) Hsiao by high-speed counter-current chromatography

Calycosin was purified from an ethyl acetate extract of the root of Astragalus membranaceus Bge. var. mongholicus (Bge.) Hsiao by high-speed counter-current chromatography. The separation was performed in two steps with a two-phase solvent system composed of n-hexane-chloroform-methanol-water (1:3:3:2, v/v). From 200 mg of the crude extract, 14.8 mg of calycosin was obtained at over 99% purity as determined by HPLC analysis, and its chemical structure was confirmed by MS, 1H and 13C nuclear magnetic resonance.

Application of analytical and preparative high-speed counter-current chromatography for separation of lycopene from crude extract of tomato paste

Lycopene was isolated from 100 mg of crude extract of tomato paste containing about 9% of lycopene. Analytical high-speed counter-current chromatography (HSCCC) was first used for the systematic selection of the two-phase solvent system. Then preparative HSCCC separation was performed with a nonaqueous solvent system composed of n-hexane-dichloromethane-acetonitrile at an optimum volume ratio of 10:3.5:6.5. This yielded 8.6 mg of lycopene at over 98.5% purity as determined by HPLC analysis.

Large-scale separation of resveratrol, anthraglycoside A and anthraglycoside B from Polygonum cuspidatum Sieb. et Zucc by high-speed counter-current chromatography

High-speed counter-current chromatography was successfully applied to the large-scale separation of resveratrol, anthraglycoside A and anthraglycoside B from the crude extract of Polygonum cuspidatum Sieb. et Zucc using a two-phase solvent system composed of chloroform, methanol and water. Resveratrol, anthraglycoside A and anthraglycoside B were separated from multigram quantities (5 g) of crude extract of P. cuspidatum. The separation yielded 200 mg to 1 g of these three compounds each at over 98% purity as determined by HPLC. The chemical structures of these components were identified by nuclear magnetic resonance (NMR) and MS.

Preparative isolation and purification of hydroxyanthraquinones from Rheum officinale Baill by high-speed counter-current chromatography using pH-modulated stepwise elution

Analytical and preparative high-speed counter-current chromatography was successfully used for the isolation and purification of hydroxyanthraquinones from Rheum officinale Baill (Dahuang) using pH-modulated stepwise elution. Four major components including chrysophanol, emodin, physcion and aloe-emodin were isolated each at over 98% purity.

Application of analytical and preparative high-speed counter-current chromatography for separation of alkaloids from Coptis chinensis Franch

Analytical high-speed counter-current chromatography (HSCCC) was used for the systematic selection and optimization of the two-phase solvent system to separate alkaloids from Coptis chinensis Franch. The optimum solvent system thus obtained led to the successful separation of alkaloids from C. chinensis Franch by preparative HSCCC. One batch separation yielded four pure alkaloids, including palmatine, berberine, epiberberine and coptisine from the crude alkaloid extract.

Multidimensional counter-current chromatographic system and its application

A multidimensional counter-current chromatographic system was set up for the first time with two sets of high-speed counter-current chromatography instruments. This system was successfully applied to the preparative separation of isorhamnetin, kaempferol and quercetin from crude flavone aglycones of Ginkgo biloba L. and Hippophae rhamnoides L. with a two-phase solvent system composed of chloroform-methanol-water (4:3:2, v/v/v).