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At least 847 records · Page 47Linked to original sources
PubMed1988

Rapid separation of flavonoids by analytical high-speed counter-current chromatography.

A commercial model of the analytical high-speed counter-current chromatography instrument was used for separation of flavonoids from a crude ethanol extract of dried fruits of sea buckthorn (Hippophae rhamnoides). Using a two-phase solvent system of chloroform-methanol-water (4:3:2), a five-fold increase in flow-rate of the mobile phase from 60 to 300 ml/h resulted in a rapid separation of five components in less than 15 min without significant loss in peak resolution. Major flavonoid component, isorhamnetin, was identified in its pure state by mass spectrometric analysis.

Countercurrent Distribution↗
PubMed1986

Immuno-affinity partition of cells in aqueous polymer two-phase systems.

Poly(ethylene glycol) (PEG) was covalently coupled to IgG antibody preparations directed against human red blood cells. This modification reduces the tendency of the antibody to agglutinate cells and increases its affinity for the upper phase in dextran-PEG aqueous two-phase systems. These effects are related to the molecular weight of the PEG used for modification and to the number of PEG molecules attached to the antibody. Exposure of human red blood cells to PEG-modified antibody causes a substantial and specific increase in cell partition into the PEG-rich phase in a number of PEG-dextran aqueous two-phase systems. Pertinent phase-system parameters were examined. Following a single incubation with PEG-derivatized antibody, a mixture of sheep and human red blood cells was completely separated in 100 min by a 30-transfer countercurrent extraction using a two phase system which normally offers little resolution.

Animals↗
PubMed1991

Protein separation with aqueous-aqueous polymer systems by two types of counter-current chromatographs.

Two different types of counter-current chromatographs, the cross-axis coil planet centrifuge (X-axis CPC) and horizontal flow-through coil planet centrifuge (horizontal CPC), were evaluated for protein separation with an aqueous-aqueous two-phase polymer system. The sample solution, containing 10-200 mg each of cytochrome c, myoglobin, ovalbumin and hemoglobin in 2 ml of each phase was eluted with the lower phase. In both instruments, the effects of the flow-rate, revolution speed, and parameter beta (helical diameters of the multilayer coil) on the protein separation were investigated. The best results were obtained from the X-axis CPC operated at 750 rpm and a flow-rate of 2.0 ml/min using a multilayer coil with a small helical diameter (beta = 0.25-0.60). Four protein samples were well resolved in less than 5 h.

Animals↗
PubMed1990

Partition coefficients and capacity factors of some nucleoside analogues.

The AIDS epidemic has brought into focus the development of antiviral agents, of which nucleoside analogues are an important class. The single most important physico-chemical property of a chemotherapeutic agent is its hydrophobicity. This paper reports the hydrophobicity, determined as log partition coefficient (P) by the shake-flask method, of 25 nucleoside analogues. The capacity factors (k') of these analogues were also obtained by reversed-phase liquid chromatography. There is a very strong linear correlation between the log P and the log k' values of all the nucleoside analogues, indicating that hydrophobicity of nucleosides can be determined by liquid chromatography. Examination of the P data indicates that an empirical mathematical relationship exists between the partition coefficient value and the molecular structure of the nucleoside analogues. A table of constants and an equation is proposed to estimate the P of nucleoside analogues.

Antiviral Agents↗
PubMed2002

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.

Astragalus Plant↗
PubMed2002

Purification of icariin from the extract of Epimedium segittatum using high-speed counter-current chromatography.

Icariin was purified from the extract of Epimedium segittatum by high-speed counter-current chromatography with a two-phase solvent system composed of n-hexane-n-butanol-methanol-water (1:4:2:6, v/v). We used two multilayer coil planet centrifuges with different capacities. A 300 mg amount of the extract was separated using a semipreparative instrument equipped with a 230-ml capacity column to yield 103 mg of icariin at 86.2% purity. An 8 g amount of the extract was separated with a large preparative instrument equipped with a 2460-ml capacity column to produce 2.45 g of icariin at 85.7% purity. From these fractions over 98% pure icariin was obtained by recrystallization with water.

Chromatography, High Pressure Liquid↗
PubMed2002

Preparative separation of isomeric sulfophthalic acids by conventional and pH-zone-refining counter-current chromatography.

Two modes of high-speed counter-current chromatography (HSCCC) were applied to separate 3- and 4-sulfophthalic acid from a mixture. Conventional HSCCC was useful for the separation of up to several hundred milligram quantities of these positional isomers, while pH-zone-refining CCC was implemented successfully to separations at the multigram level. The conventional HSCCC separations were performed with a standard J-type HSCCC system that has a superior resolution but a lower level of retention of the stationary phase of the biphasic solvent system used (acidified n-butanol-water). The pH-zone-refining CCC separations were performed with an X-type HSCCC system (a cross-axis system) that has a higher capability for retention of the stationary phase. The purified positional isomers (over 99% pure as determined by HPLC) were characterized by 1H NMR and negative ion electrospray ionization mass spectrometry.

Chromatography, High Pressure Liquid↗
PubMed2002

Separation of salidroside from Rhodiola crenulata by high-speed counter-current chromatography.

High-speed counter-current chromatography (HSCCC) was used to purify salidroside from an extract of Rhodiola crenulata with two steps using a two-phase solvent system composed of ethyl acetate-n-butanol-water (1:4:5, v/v) in the first run and chloroform-methanol-isopropanol-water (5:6:1:4) in the second run. The method yielded 21.9 mg of salidroside from 1.216 g of the crude sample at 98% purity determined by HPLC analyses. Identification was performed by 1H NMR, 13C NMR, and MS.

Countercurrent Distribution↗
PubMed2002

Purification of (+)-dihydromyricetin from leaves extract of Ampelopsis grossedentata using high-speed countercurrent chromatograph with scale-up triple columns.

Purification of (+)-dihydromyricetin from an extract (16 g) of leaves of Ampelopsis grossedentata was performed using a preparative triple-column countercurrent chromatograph. With a solvent system composed of n-hexane-ethyl acetate-methanol-water (1:3:2:4, v/v) 11.3 g of (+)-dihydromyricetin was obtained at a high purity of over 99% by HPLC at 254 nm in 9 h.

Ampelopsis↗
PubMed2002

Purification of long-chain fatty acid ester of epigallocatechin-3-O-gallate by high-speed counter-current chromatography.

Epigallocatechin-3-O-gallate (EGCG) was modified by catalytic esterification with hexadecanoyl chloride. A long-chain fatty acid ester derivative was obtained from the purification of this reaction product by high-speedcounter-current chromatography using a solvent system composed of n-hexane-ethyl acetate-methanol-water (1:1:1:1, v/v). The structure of the derivative, epigallocatechin-3-O-gallate-4'-hexadecanate, was elucidated by IR, MS and 1H NMR.

Catechin↗
PubMed2003

Separation of andrographolide and neoandrographolide from the leaves of Andrographis paniculata using high-speed counter-current chromatography.

The bioactive diterpenes andrographolide and neoandrographolide from the leaves of Andrographis paniculata NEES (Acanthaceae) were successfully separated by counter-current chromatography. A single 280-min separation yielded 189 mg of 99.9% andrographolide and 9.5 mg of 98.5% neoandrographolide applying water-methanol-ethyl acetate-n-hexane (2.5:2.5:4:1) solvent system. Structure confirmation was done by electrospray MS, one-dimensional NMR experiments, circular dichroism, optical rotation dispersion, and specific optical rotation [alpha]D.

Andrographis↗
PubMed2003

Isolation and identification of four flavonoid constituents from the seeds of Oroxylum indicum by high-speed counter-current chromatography.

Four flavonoids, chrysin, baicalein, baicalein-7-O-glucoside, baicalein-7-O-diglucoside (Oroxylin B) and one unknown flavonoid have been isolated and purified for the first time in the seeds of Oroxylum indicum by high-speed counter-current chromatography with a two-phase solvent system composed of chloroform-methanol-water (8:10:5, v/v). Then, 50 mg baicalein-7-O-glucoside, 10.5 mg baicalein-7-O-diglucoside, 4.5 mg chrysin-7-O-diglucoside, 25 mg baicalein and 45 mg chrysin could be obtained after injecting 20 mg/ml sample extract ten times and their purities were 96, 90, 85, 95 and 98%, respectively. All these constituents were identified by high-performance liquid chromatography-mass spectrometry and nuclear magnetic resonance.

Bignoniaceae↗
PubMed2003

Linear two-step gradient counter-current chromatography analysis based on a recursive solution of an equilibrium stage model.

The implementation of gradients in continuously operated chromatographic counter-current processes has recently attracted considerable interest as a method to improve the performance of this effective separation method. If liquid mobile phases are applied it is advantageous to set the solvent strength in the desorbent stream higher than that in the feed stream. As a consequence. the components to be separated are more retained in the adsorption zones and more easily eluted in the desorption zones. Due to the additional degrees of freedom the design and the optimization of such a two-step gradient counter-current process is difficult. In this paper a steady state equilibrium stage model is used to simulate the process under linear conditions. A simple solution of the underlying model equations is presented capable to describe efficiently the unit for large stage numbers typically encountered in chromatographic columns. Due to the rapidity of the algorithm developed a broad range of operating conditions can be evaluated systematically for different types of gradients. The impact of (a) the functional dependence of the adsorption equilibrium constants on the solvent composition, (b) the number of equilibrium stages and (c) the specification of purity requirements is illustrated and discussed based on results of parametric calculations. The results achieved emphasize the potential of two-step gradient counter-current chromatography.

Countercurrent Distribution↗
PubMed2003

Purification of quinoline yellow components using high-speed counter-current chromatography by stepwise increasing the flow-rate of the mobile phase.

Quinoline yellow (Color Index No. 47005) consists of multiple components that show a large difference in their partition coefficients (K), ranging from 0.03 to 3.3 in the solvent system tert.-butyl methyl ether (MTBE)-1-butanol-acetonitrile-aqueous 0.1 M trifluoroacetic acid (TFA). Consequently, it requires an excessively long elution time for the simultaneous separation of all components by the standard high-speed counter-current chromatography technique, which uses a constant flow-rate of the mobile phase. In order to overcome this problem, we increased the flow-rate of the mobile phase stepwise from 0.1 to 2.0 mL/min. Using this new procedure, six components (0.2-6.1 mg) were successfully isolated from 25 mg of a commercial quinoline yellow preparation in a single run using a two-phase solvent system composed of MTBE-1-butanol-acetonitrile-aqueous 0.1 M TFA (1:3:1:5, v/v). The purified components were analyzed by high-performance liquid chromatography, electrospray ionization mass spectrometry, and nuclear magnetic resonance spectroscopy.

Countercurrent Distribution↗
PubMed2003

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.

Astragalus propinquus↗
PubMed2003

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.

Countercurrent Distribution↗