Preparative chromatography counter current

Until separation techniques such as chromatography (28,29) and counter-current extraction had advanced sufficientiy to be of widespread use, the principal alkaloids were isolated from plant extracts and the minor constituents were either discarded or remained uninvestigated. With the advent of, first, column, then preparative thin layer, and now high pressure Hquid chromatography, even very low concentrations of materials of physiological significance can be obtained in commercial quantities. The alkaloid leurocristine (vincristine, 22, R = CHO), one of the more than 90 alkaloids found in Catharanthus roseus G. Don, from which it is isolated and then used in chemotherapy, occurs in concentrations of about 2 mg/100 kg of plant material. 

Ito, Y., Efficient preparative counter-current chromatography with a coil planet centrifuge, J. Chromatogn, 214, 122, 1981. 

High performance liquid chromatography (HPLC) has been by far the most important method for separating chlorophylls. Open column chromatography and thin layer chromatography are still used for clean-up procedures to isolate and separate carotenoids and other lipids from chlorophylls and for preparative applications, but both are losing importance for analytical purposes due to their low resolution and have been replaced by more effective techniques like solid phase, supercritical fluid extraction and counter current chromatography. The whole analysis should be as brief as possible, since each additional step is a potential source of epimers and allomers. 

Wei, Y. et ah. Application of analytical and preparative high-speed counter-current chromatography for separation of lycopene from crude extract of tomato paste, J. Chromatogr. A, 929, 169, 2001. 

At present, it has only been possible to isolate and identify high concentrations of one compound, isorhamnetin, from pollen of Phleum pretense using high-speed counter-current chromatography. This does not reflect the lack of proper technology, but rather the preparation, time and expense of isolating cryptic and perhaps ephemeral compounds via techniques involving more sophisticated HPLC and mass spectrometry. Consistent with the author s earlier hypothesis that an isorhamnetin class... 

A. Weisz, E. P. Mazzola, J.E. Matusik and Y. Ito, Preparative separation of isomeric 2-(2-quinolinyl)-lH-indene-l,3(2H)-dione monosulfonic acids (6SA and 8SA) of the color additive D C Yellow No. 10 (Quinoline Yellow) by pH-zone refining counter-current chromatography./. Chromatogr.A, 923 (2001) 87-96. 

Kohler N, Wray V, Winterhalter P (2008) Preparative isolation of procyanidins from grape seed extracts by high-speed counter-current chromatography. J Chromatogr A 1177 114-125... 

Degenhardt, A. et al.. Preparative separation of polyphenols from tea by high-speed counter-current chromatography, J. Agric. Food Chem., 48, 3425, 2000. 

In order to obtain sufficient quantities of these phytoecdysones for more detailed biological studies, droplet counter-current chromatography (DCCC) was adapted . DCCC Is an especially efficient method for the preparative separation of polar compounds like the phytoecdysones. Thus with DCCC, while requiring only small volumes of solvent, more than 50 mg of each of the Ajuga phytoecdysones were rapidly and nondestructlvely separated and fully recovered (Fig. 6) from each 500 mg Injection. 

When the separation procedures described in detail above are unsatisfactory for the separation of a mixture of organic compounds, purely physical methods may be employed. Thus a mixture of volatile liquids may be fractionally distilled (compare Section 2.26) or a mixture of non-volatile solids may frequently be separated by making use of the differences in solubilities in inert solvents. The progress of such separations may be monitored by application of the various chromatographic techniques detailed in Section 2.31, or indeed these techniques may be employed on the preparative scale for effecting the separation itself (e.g. flash chromatography, p. 217). The techniques of counter current distribution, fractional crystallisation or fractional sublimation (Section 2.21) may also be employed where appropriate. 

The alkaloids were best isolated from the ethanol extract of the plant material, partially fractionated by counter-current distribution, and subsequently purified by preparative chromatography. Of the 11 known Cephalotaxus alkaloids (105-115 in Figs. 8 and 9), cephalotaxine (105a) is ubiquitous and the most abundant (up to 64% of the total alkaloid extract) in all species examined. C. wilsoniana Hay., which yields only minor quantities of cephalotaxine, is the exception, however it is rich in Homoerythrina alkaloids,... 

Ito, Y. Cross-axis synchronous flow-through coil planet centrifuge free of rotary seals for preparative counter-current chromatography. Part I Apparatus and analysis of acceleration. Sep. Sci. Technol. 1987, 22, 1971. 

Marston, A. Hostettmann, K. Counter-current chromatography as a preparative tool—Applications and perspectives. J. Chromatogr., A 1994, 658, 315-341. 

Whether medium-pressure liquid chromatography (MPLC), counter-current chromatography (CCC), or preparative thin-layer chromatography (PTLC) was used. 

Most of the development work on preparative liquid chromatography has been restricted to batch chromatography and batch systems and only comparatively recently has it been extended to continuous chromatography. For separations at pressures up to 30 bar a counter-current machine is commercially available. A schematic diagram of such a chromatograph, the so-called sequential separator... 

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