ABSTRACT
This chapter shows that secondary metabolites have been valuable, occasionally even indispensable, in classifications that are expected to be unequivocal and stable. Gross separations were originally introduced using paper chromatography or chemical paper tests, but these have not been used recently in chemotaxonomy except in a few simple diagnostic tests. Gas chromatography (GC) has mostly been used for volatile chemical compounds. High-performance liquid chromatography (HPLC) has become the method of choice for most nonvolatile secondary metabolites. HPLC using gradient elution on reversed-phase material allows a good separation of a large range of secondary metabolites with different polarities, and Ultra Violet (UV) and fluorescence detectors can be used to detect small amounts of most compounds with a chromophore. Diode array detection is particularly relevant in connection with HPLC but can also be used with micellar capillary electrophoresis (MCE). Certain secondary metabolites fluoresce strongly and so can be detected in very low amounts with a fluorescence detector.
