Knowledge is of two kinds. We know a subject ourselves, or we know where we can find information on it Samuel Johnson, 18 April, 1775* Sterols are among the most studied groups of natural products with interest commencing in the 19th century and running to the present. Investigations have embraced the refinement of separation procedures, the development of new analytical techniques and instrumentation for structure elucidation, the unravelling of biosynthetic mechanisms, the determination of the physiological functions of sterols, and the role they play in health and disease. In the past 20-30 years interest in the medical implications of sterol biochemistry, studies on the sterols of plants, algae and fungi, and the identification of the many unusual sterols from marine organisms have proceeded in parallel and somewhat independently. Although the motiva tion and goals for the various lines of investigation have differed widely the researchers working in each of these areas have contributed a wealth of knowledge to the literature relating to the analysis of sterols and many diverse new sterols have been discovered. We conceived this book as a modest attempt to bring together some of this literature in the hope that it may be helpful to newcomers to sterol research. We had originally intended to produce a 'handbook' outlining in detail the protocols to be followed for sterol extraction, chromatography, NMR analysis, etc. in order to identify the components of a sterol mixture.
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ISBN-13
978-94-009-1447-6 (9789400914476)
DOI
10.1007/978-94-009-1447-6
Schweitzer Klassifikation
1 Nomenclature and biosynthesis of sterols and related compounds.- 1.1 Introduction.- 1.2 IUPAC-IUB recommended nomenclature for steroids and triterpenoids.- 1.3 The biosynthesis of sterols and triterpenes.- 2 Extraction of sterols from tissues.- 2.1 Introduction.- 2.2 Extraction methods.- 2.3 Separation of sterols from extracted lipids.- 2.4 Examples of the extraction of sterols.- References.- 3 Initial separation methods.- 3.1 Introduction.- 3.2 Digitonin precipitation of sterols.- 3.3 Separation of free sterols and steryl conjugates from a total lipid by adsorption column chromatography.- 3.4 Thin-layer chromatography.- 3.5 The use of mini-columns for the preliminary separation of sterol fractions.- 3.6 Hydrolysis of steryl conjugates.- 3.7 Silver nitrate or argentation chromatography.- 3.8 Autoxidation and isomerization of sterols.- References.- 4 High-performance liquid chromatography of sterols.- 4.1 Introduction.- 4.2 Normal- and reversed-phase HPLC.- 4.3 HPLC detectors.- 4.4 HPLC of sterol derivatives.- 4.5 Influence of column temperature on sterol separation by HPLC.- 4.6 Retention data of sterols on HPLC.- 4.7 Sterol separation factors on HPLC.- 4.8 Differentiation of C-24 epimers of 24-alkylsterols on reversed-phase HPLC.- References.- 5 Gas-liquid chromatography of sterols.- 5.1 Introduction.- 5.2 Packed columns and the stationary phase.- 5.3 Capillary columns.- 5.4 Sample injection and detection.- 5.5 Derivatization of sterols.- 5.6 Preparative GC.- 5.7 Retention time data.- 5.8 Separation factors.- 5.9 GC of the C-24 epimers of 24-alkylsterols.- 5.10 GC of steryl conjugates.- References.- 6 Infrared and ultraviolet spectroscopy of sterols.- 6.1 Introduction.- 6.2 Infrared spectroscopy.- 6.3 Ultraviolet spectroscopy.- References.- 7 Mass spectrometry of sterols.- 7.1 Introduction.- 7.2 Sample ionization.- 7.3 Derivatives used for mass spectrometry of sterols.- 7.4 Mass-spectral fragmentations of the sterol rings.- 7.5 Mass-spectral fragmentations of the sterol side chain.- 7.6 Mass spectra of tetracyclic and pentacyclic triterpene alcohols.- 7.7 Mass spectrometry of steryl conjugates.- References.- 8 1H NMR spectroscopy of sterols.- 8.1 Introduction.- 8.2 Methyl signals.- 8.3 Methine and olefinic protons.- 8.4 Quantitative estimation of C-24 epimeric 24-alkylsterol mixtures.- 8.5 Aromatic solvent induced shifts (ASIS).- 8.6 Lanthanide-induced shifts (LIS).- References.- 9 13C NMR spectroscopy of sterols.- 9.1 Introduction.- 9.2 Methods for signal assignments.- 9.3 13C Chemical shift data of sterols and triterpene alcohols.- References.- 10 One-dimensional and two-dimensional NMR spectroscopy of sterols.- 10.1 Introduction.- 10.2 ID NMR spectroscopy.- 10.3 2D NMR spectroscopy.- 10.4 Connectivity diagrams for use with 2D NMR data.- 10.5 Generalized 1D and 2D strategies for sterols and related compounds.- 10.6 Complete assignments of 1H NMR spectra of sterols.- References.- 11 X-ray crystallography of sterols.- References.- 12 Sources of sterols.- 12.1 Introduction.- 12.2 4-Desmethylsterols.- 12.3 Large-scale purification of 4-desmethylsterols.- 12.4 Sterols with methyl groups at C-4 and/or C-14.- 12.5 Tetracyclic triterpene alcohols.- 12.6 Pentacyclic triterpene alcohols and ketones.- 12.7 The use of inhibitors of sterol biosynthesis to produce specific sterols.- 12.8 Sources of sterols and tetra- and pentacyclic triterpenes.- References.- Appendix 1 The trivial names of sterols.- Appendix 2 Structures of pentacyclic triterpenes.- Appendix 3 Physical data of selected sterols and triterpenes.- Appendix 4 The quantification of sterols.
