Naturally occurring thin-layer chromatography

The methods employed for isolation of the alkaloids depend on the nature of the compounds, and specific conditions have frequently been devised for the selective isolation of particular types of compounds. Usually, fresh or dried plant material is extracted with dilute acid solution or with alcohol, and the extract obtained is further fractionated by extraction into organic solvents with variation of pH. Extraction columns (288), membrane processes (425), and ion-exchange materials (288-290) may be particularly useful for subfractionation or isolation procedures. For further identification and isolation of separate compounds, preparative thin-layer chromatography, (288, 291, 292, 426), liquid chromatography (293, 294), or gas chromatography may be used (202, 296, 297). Because some of the products reviewed in this chapter occur naturally in very small amounts, they have not been isolated in crystalline form. Gas chromatography-mass spectrometry (87, 213, 299), mass fragmentography (192), and mass spectrometry-mass spectrometry (301, 359) have proved to be particularly useful techniques for identification of trace alkaloids in complex mixtures. 

C assy tha filiformis also showed traces of the presence of 0-methylcassy-filine (XCVIII) on the basis of comparisons of the NMR-spectra of chromatographic fractions in which it predominated with the spectrum of authentic 0-methylcassyfiline prepared from cassyfiline, (XVIIb), and by comparative thin-layer chromatography. However, the naturally occurring 0-methylcassyfiline was not isolated in pure form. This base would correspond to norocoteine (13a). 

J7. Jones, K., and Heathcote, J. G., The rapid resolution of naturally occurring amino acids by thin-layer chromatography. J. Chromatogr. 24, 106-111 (1966). 

Figure 25 Synthesis of various d-lysergyl peptide lactams catalysed by d-lysergyl peptide synthetase (LPS). Compounds formed from [9-10- H]dihydrolysergic acid, proline and different combinations of two amino acids occurring in the position of the natural ergopeptines were extracted from reaction mixtures, separated by thin-layer chromatography and analysed. The structures of the indicated bands are given. The indicated lanes contain products from reactions mixtures of LPS with [9-10- H]dihydrolysergic acid, proline, ATP and alanine+phenylalanine (1), a-aminobutyric acid (Abu)+phenylalanine (2), valine+phenylalanine (3), valine+leucine (4), a-aminobutyric acid+leucine. All amino acids were present in saturating conditions...

Abramson, D., and M. Blecher Quantitative two-dimensional thin-layer chromatography of naturally occurring phospholipids. J. Lipid Res. 6, 628 (1964). 

Arvidson, G. a. E. Fractionation of naturally occuring lecithins according to degree of unsaturation by thin-layer chromatography. J. Lipid Res. 6, 574 (1965). 

Thin-layer Chromatography.— Improved or more-rapid separations by t.l.c. have been reported for mono-, di-, tri- and oligo-saccharides, naturally occurring pentitols and hexitols, iridoid D-glucopyranosides, methylated nucleosides, " and D-arabinosyl-, o-ribosyl-, and 2-deoxy-D-ery Aro-pentosyl-nucleotides. " ... 

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