Comparative analysis of the underground parts ofGentiana species by HPLC with diode-array and mass spectrometric detection

Summary The aim of this work was to compare the chemical composition of the underground parts (roots and rhizomes) ofGentiana cruciata L.,Gentiana pneumonanthe L., andGentiana asclepiadea L.— the three gentians native to Hungary—with that of the widely used stomachicGentiana lutea L., to determine which of the three Hungarian species could be used as a substitute forGentiana lutea in pharmaceutical preparations. The four gentians were compared by means of RPHPLC with diode-array detection (DAD) and electrospray ionization-mass spectrometric detection (ESI-MSD). The quantities of the lead compounds, the secoiridoid-glycosides, in 220 samples of the underground parts of gentians originating from several locations in Hungary, were determined by a more economical RPHPLC-DAD method. The occurrence of the characteristic compounds investigated—bitter principles and xanthones—in the underground parts of the speciesGentiana asclepiadea L. suggest it might be a potential replacement forGentiana lutea L. in pharmaceutical products. Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001     

Sample preparation and isolation using planar chromatographic methods

The state of art of the various preparative planar liquid chromatographic (PLC) methods is summarized, especially for off-line and on-line sample application. The sample purification possibilities for PLC techniques are discussed. Purification and isolation strategies using forced-flow planar chromatographic techniques, such as overpressured layer chromatography and rotation planar chromatography, are suggested in the form of flow charts.     

Sequential centrifugal layer chromatography (SCLC): A new technique for the isolation of natural compounds. Part 2: Comparative study on centrifugal layer chromatography (CLC) and SCLC for the separation of furocoumarin isomers

The new sequential centrifugal layer chromatography extends the possibilities for preparative separation of furocoumarin isomers. In the present work, isobergapten, pimpinellin, bergapten, isopimpinellin, and sphondin were isolated from a prepurified extract of Heracleum sphondylium roots using two different techniques, namely, centrifugal layer chromatography (CLC) and sequential centrifugal layer chromatography (SCLC). The former technique was carried out with four plates, whereas the latter method required only one plate, using the same mobile phase in each case. A further advantage of the SCLC method was that all completely separated compounds could be quickly and efficiently eluted in small volumes of mehtanol.     

Solid-liquid extraction strategy on the basis of solvent characterization

Summary Different solvents used for extraction are characterized on the basis of the Snyder theory. The individual solvent strength (s_i) and selectivity values (s_v) of the solvents are used to formulate an extraction strategy by use of selected solvents, in a manner similar to that used for the computer-aided HPLC and TLC “PRISMA” mobile phase optimization procedures. After a pre-assay using the nine proposed solvents, twelve measurements are necessary to obtain the global optimum. The new method allows successful solid-liquid extraction of compounds from biological matrices such as medicinal and aromatic plants. Data obtained from furocoumarin isomers and flavonoid glycosides extracted from different medicinal and aromatic plants are used to demonstrate the validity of the method. The structures and properties of the compounds to be extracted do not have to be known for the procedure to be used. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

Stationary phase optimized selectivity liquid chromatography: Basic possibilities of serially connected columns using the "PRISMA" principle

A new procedure (stationary phase optimized selectivity liquid chromatography: SOS-LC) is described for the optimization of the HPLC stationary phase, using serially connected columns and the principle of the "PRISMA" model. The retention factors (k) of the analytes were determined on three different stationary phases. By use of these data the k values were predicted applying theoretically combined stationary phases. These predictions resulted in numerous intermediate theoretical separations from among which only the optimal one was assembled and tested. The overall selectivity of this separation was better than that of any individual base stationary phase. SOS-LC is independent of the mechanism and the scale of separation.     

The role of planar chromatography in medicinal plant research

This paper summarizes the role of planar chromatography (PC) in medicinal and aromatic plant (MAP) research and development, and demonstrates the importance of the technique, after extraction, in the analysis of MAP (identification and quantitative determination of the separated compound/s), in the purification and isolation process, and in different types of screening procedure. Special attention is paid to analytical, micropreparative and preparative forced-flow techniques, for example overpressured-layer chromatography (OPLC) and rotation planar chromatography (RPC). The special features of analytical, micropreparative, and preparative layer chromatography (PLC), OPLC, and RPC are compared in tables. Purification and isolation procedures using forced-flow techniques are shown in flowcharts. Some applications, relating to different classes of substance, are presented to demonstrate the versatility of various planar chromatographic techniques.     

The “disturbing zone” in overpressure layer chromatography (OPLC)

This paper describes the fundamental factors causing the “disturbing zone” in OPLC. This phenomenon of distorted substance zones appears when the OPLC separation is started with a dry layer and is due to interaction between the gas that is physically bound to the surface of the sorbent (m_a) and the gas molecules dissolved in the eluent (m_s). Possibilities for elimination of the adverse effects of disturbing zones ultimately depend on the establishment of operating conditions that inhibit their initial formation. Since modification of the location of the disturbing zone is only possible within a very narrow range, the sole solution to this problem is to conduct a pre-run, which may be carried out with hexane in the case of separation of apolar compounds. For separation of polar substances, the pre-run may also be performed with hexane or with a solvent of the mobile phase in which the components are unable to migrate. The selection of this solvent may be considered during the optimization of the eluent system.