Plant extracts chromatographic systems

GENERAL PRINCIPLES OF THE CHOICE OF CHROMATOGRAPHIC SYSTEMS IN PLC OF PLANT EXTRACTS... 

The choice of the chromatographic system depends on the chemical character of the extracts being separated. The mobile phase should accomplish all requirements for PLC determined by volatility and low viscosity, because nonvolatile components (e.g., ion association reagents and most buffers) should be avoided. It means that, for PLC of plant extracts, normal phase chromatography is much more preferable than reversed-phase systems. In the latter situation, mixtures such as methanol-ace-tonitrile-water are mostly used. If buffers and acids have to be added to either the... 

Supercritical fluid extraction (SFE) is today an important technique for the extraction of a large number of differing analytes from various matrices such as pollutants from soils, fats from food stuffs, active substances from plants, and additives from polymers. The obtained extracts are normally analyzed on a chromatographic system even though other... 

At the end of the 1930s, adsorption chromatography in columns as introduced by Tswett had become a powerful separation technique for plant extracts and natural products. Simultaneously, the need for a more rapid alternative suitable for identification of separated substances led to the invention of an open chromatographic system. In 1938, Izmailov and Shraiber reported the separation of belladonna alkaloids on a thin adsorbent layer, coated onto microscopic slides. Development of circular chromatograms was achieved by placing small amounts of various solvents to the center of samples previously applied as spots onto the layer. This method was an extremely rapid microtechnique requiring only small amounts of stationary and mobile phases. 

However, antioxidant screening in complex mixtures of plant origin requires simple and rapid in vitro models for a possible combination with chromatographic techniques such as TLC, HPLC, HSCCC, or CPC. The reduction of the stable free-radical DPPH (l,l-diphenyl-2-picryUiydrazyl) by antioxidant substances is currently the most widely used chemical test for the screening of plant extracts. Only a few bioassay-guided fractionation processes have also evaluated the antimicrobial, antibacterial activity, or cytotoxicity of fractions enriched in specific flavonoids by using HSCCC or CPC liquid-liquid systems [30, 35]. 

Matysik, G., and Soczewinski, E. (1996). Computer-aided optimization of stepwise gradient TLC of plant extracts. J. Planar Chromatogr.—Mod. TLC 9 404-412. Matyska, M., and Soczewinski, E. (1993). Optimization of chromatographic systems in TLC by graphical method and with a computer program. Chem. Anal. (Warsaw) 38 555-563. 

The results in Table I show that, in the presence of plant material, the standard GA3 is spread over a considerably wider range than is usual. However, after the sample is further purified by the second run, the mobility of GA3 returns to normal. The same pattern of distribution, with zone III as maximum, is manifest in the natural run, although at considerably lower fluorescent intensities. For both fractions, the presence of GA3 is confirmed by the capryl system. A portion of zone III of the natural extract gave positive response proportional to concentration in the pinto bean seedling assay and in the dwarf maize mutants I and V assay. The relative activity on both mutants was approximately equal, as is required for GA3 (26). The correlation of relatively specific biological growth activity with chromatographic and chemical behavior affirms the presence of a GA3-like substance in kudzu vine. 

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