Chromatographic investigations of furocoumarins fromHeracleum genus fruits

Summary Furocoumarins from extracts ofHeracleum genus fruits were separated using normal and reversed phase TLC and HPLC and isolated in the milligram scale using overloaded systems of column chromatography. Binary or ternary solvents containing a polar modifier (methanol, diisopropyl ether or acetonitrile) were used as the mobile phases. Preliminary report on this work was presented at the 47th International Congress of Pharmaceutical Sciences of F.I.P. in Amsterdam. The Netherlands, 30 August–5 September 1987.     

Comparison of the Microbiological Activities of Different Varieties of Hop (Humulus lupulus) Extracts by Thin-Layer Chromatography—Direct Bioautography

JPC – Journal of Planar Chromatography – Modern TLC - Commercially available hop pellets of different origins were extracted by use of ethanol and water, chromatographed on silica...     

Low-Temperature TLC-MS of Essential Oils from Five Different Sage (Salvia) Species

JPC – Journal of Planar Chromatography – Modern TLC - In a previous paper we discussed the possibility of fractionating the essential oils of different sage species by low-temperature...     

Two-dimensional thin-layer chromatography with adsorbent gradient as a method of chromatographic fingerprinting of furanocoumarins for distinguishing selected varieties and forms of Heracleum spp

There are a lot of taxonomic classifications of the genus Heracleum, and many authors indicate they need revision. Morphological identification is difficult to perform, as there are only few characteristic differences between each Heracleum species, varieties and forms. Furanocoumarins are characteristic compounds for the Apiaceae family, and they can be found in the whole genus in large quantities. Despite this fact, it is difficult to use the furanocoumarin profiles of plants, for their discrimination, as furanocoumarins are difficult to separate, due to their similar chemical structures and physicochemical properties. In this paper, a new, simple method is proposed for the discrimination of selected species, varieties and forms of the genus Heracleum. Thin-layer chromatography (TLC) with an adsorbent gradient (unmodified silica gel+octadecylsilica wettable with water) enables complete separation of the structural analogues. The proposed method gives the possibility to distinguish selected species, varieties and forms of the Heracleum genus, as they produce distinctive furanocoumarin fingerprints. The method is characterised by high specificity, precision, reproducibility and stability values. It is for the first time that graft TLC is used for constructing fingerprints of herbs. The complete separation of ten structural analogues, by combining gradient TLC with the unidimensional multiple development technique, has not been reported yet.     

Thin-layer chromatography of alkaloids on cyanopropyl bonded stationary phases. Part I

Selected alkaloids are chromatographed on cyanopropyl-silica thin layers using various nonaqueous and aqueous eluents. Because of the strong retention of these basic compounds, nonaqueous eluents containing medium polar diluents, strongly polar modifiers, and silanol blockers (ammonia or diethylamine) are required for separation. Likewise, aqueous eluents containing modifiers (acetonitrile, methanol, and tetrahydrofuran), buffered aqueous solutions at pH 2-8, ion-pair reagents [octane sulfonic acid sodium salt, sodium dodecyl sulphate, and bis-(2-ethylhexyl)phosphoric acid], or silanol blockers (ammonia, tetrabutyl ammonium chloride, and diethyl amine) are investigated. The separation selectivity as well as spot symmetry and efficiency system in the applied eluent systems are analyzed. The most selective and efficient systems are used in two-dimensional separations of isoquinoline alkaloids' mixture and the plant extracts Chelidonium majus, Fumaria officinalis, and Glaucium flavum. Two-dimensional thin-layer chromatography on cyanopropyl layer with diode array detection densitometry enables the separation and identification of some alkaloids in plant extracts.     

Retention process in reversed phase TLC systems with polar bonded stationary phases

The retention of a solute in RP chromatography is a very complex process which depends on many factors. Therefore, the study of the influence of a mobile phase modifier concentration on the retention in different reversed phase chromatographic systems is very important for understanding the rules governing retention and mechanisms of substance separation in a chromatographic process. Composition changes and the nature of mobile phases enable tuning of the separated analytes' retention over a wide range of retention parameters and optimization of the chromatographic process as well. Optimization of the chromatographic process can be achieved by several different methods; one of them is the so-called interpretative strategy. The key approach adopted in this strategy is the implementation of adequate retention models that couple the retention of solute with the composition of a mixed mobile phase. The use of chemically bonded stationary phases composed of partially non-bonded silica matrix and organic ligands bonded to its surface in everyday chromatography practice leads to questions of the correct definition of the retention model and the dominant retention mechanism in such chromatographic systems. The retention model for an accurate prediction of retention factor as a function of modifier concentration and the heterogeneity of the adsorbent surface should be taken into consideration. In this work the influence of mobile-phase composition on the retention of sixteen model substances such as phenols, quinolines, and anilines used as test analytes in different RP-TLC systems with CN-, NH2-, and Diol-silica polar bonded stationary phases has been studied. The aim of this study is to compare the performance of three valuable retention models assumed as the partition, adsorption/partition, and adsorption mechanism of retention. All the models were verified for different RP-TLC systems by three statistical criteria. The results of investigations presented in this work demonstrate that the best agreement between the experimental and calculated Rf values was obtained by the use of new-generation retention models, which assume heterogeneity of adsorbent surface. The results reported here show that heterogeneity of the adsorbent surface may be important in analysis of the elution process in liquid chromatography. Consideration of the goodness of fit for the experimental data to the examined retention models is in conformity with the adsorption mechanism of retention on all polar bonded stationary phases in most eluent systems for most investigated compounds.     

The effect of chromatographic conditions on the separation of selected alkaloids in RP-HPTLC

Selected alkaloid standards were chromatographed on C18 W layers using various aqueous eluents containing an organic modifier and pH 3 buffer to suppress silanol ionization or an organic modifier and pH 8 buffer to suppress alkaloid ionization. Anionic ion pairs such as sodium dodecyl sulfate, octane-1-sulfonic acid sodium salt, pentane-1-sulfonic acid sodium salt, and bis(2-ethylhexyl)ortho-phosphoric acid are used to improve peak shape, efficiency, and selectivity. Amines (e.g., diethylamine, triethylamine, and tetrabutylamonium chloride) are incorporated into mobile phases to block surface silanols. The effect of chromatographic conditions on the separation of the investigated alkaloids is analyzed by the comparison of particular densitograms, asymmetry factor, or theoretical plate number. The best efficiency, peak symmetry, and separation selectivity of the investigated compounds is obtained through the addition of amine (especially diethylamine) to the mobile phases.     

The Effect of Chromatographic Conditions on the Separation of Selected Alkaloids on Silica Layers

JPC – Journal of Planar Chromatography – Modern TLC - Alkaloid standards have been chromatographed on silica layers with a variety of aqueous and nonaqueous mobile phases. The effect on...     

Characterization of Mint Essential Oils by High-performance Liquid Chromatography and Chemometrics

The raw material from Mentha piperita L, M. arvensis L, M. longifolia L, M. spicata, and M. suaveolens from various locations were extracted using steam distillation to obtain the mint essential oils. High-performance liquid chromatography was used to obtain fingerprints of the mint samples. SpecAlign, Savitzky–Golay, recursive alignment by fast Fourier transform, Pearson’s correlation coefficient, and principal component analysis were used to characterize the chromatograms. The results were used to confirm the similarities of M. longifolia collected in Ostrowsko, Poland in 2013 and 2014. The considerable similarity of these M. longifolia samples demonstrates that the reported chemometric approach is suitable for the classification of plant materials.     

TLC-MS versus TLC-LC-MS fingerprints of herbal extracts. Part III. Application of the reversed-phase liquid chromatography systems with C18 stationary phase

In the previous paper from this series, we proposed mass spectrometric fingerprinting of complex botanical samples upon the examples of the pharmacologically important phenolic acids and flavonoids selectively extracted from Salvia lavandulifolia. In this study, we explore fingerprinting efficiency with a novel two-dimensional analytical system composed of the reversed-phase thin-layer chromatography and the reversed-phase high performance liquid chromatography with mass spectrometric detection (2D RP-TLC-RP-LC-MS). We also compare its efficiency with that of the one-dimensional analytical system (the reversed-phase thin-layer chromatography with mass spectrometric detection; 1D RP-TLC-MS). As our present study is basically focused on the method development, we considered it as justified to carry out our comparison with the phenolic acid extracts selectively derived from the Salvia lavandulifolia species, similar as it was done in Part II from this series. Upon the results obtained, it was established that the 1D RP-TLC-MS mode and the 2D RP-TLC-RP-LC-MS mode can be applied to fingerprinting of herbal extracts, and that the 2D RP-TLC-RP-LC mode can provide a more abundant information than that originating from the 1D RP-TLC mode.