Secondary metabolites concept

The enormous diversity of microorganisms is a factor that must be kept in mind for future drug development. Only a minor proportion of bacteria and fungi have been cultured or examined for secondary metabolite production. For example, only 5% of the total number of fungal species have been described. Of those described (69,000), only 16% (11,500) have been cultured. It has been estimated that 1 gram of soil contains 1000 to 10,000 species of undiscovered prokaryotes The extensively used concept of isolation of microbial strains fixim different geographical and climatic locations around the world still gathers support. ... 

Recently, Merck KGaA in Darmstadt in cooperation with AnalytiCon AG (Berlin) presented a HPLC-based Workstation (SepBox) designed for the extraction and separation of plant material in a more preparative scale which has also successfully been used for the separation of secondary metabolites from culture broths of microorganisms. On the other hand, it has been shown that automated solid phase extraction (SPE) can achieve high quality samples from cultivation of microorganisms in an easy and cost-effective manner. In the latter case modified Zymark RapidTrace modules have been used in the automation concept which advantageously does not need HPLC-techniques [353]. 

The concept of primary and secondary metabolites is outlined and it is concluded that an exact definition is not especially useful. The coexistence of metabolites and the cellular machinery for their transformation is outlined by the concept of com-partmentation (Appendix 1). Tertiary metabolites and xenochemicals are defined for the sake of completeness (Section 2.1) and the current theories of the function of secondary metabolites are briefly discussed (Section 2.2). 

---