Special Problems with the Extraction of Plants

There is increasing scientific interest in the extraction and isolation of secondary metabolites from plants; for example, as part of biosynthetic, biochemical, chemotaxonomic, ecological, phytochemical, pharmacological, and plant tissue culture studies. This chapter is intended to provide guidance for those interested in phytochemistry and intending to work on the isolation of secondary metabolites from plants of new and known structure. The secondary metabolites of plants are compounds with no apparent function in the primary metabolism of the organism, and these substances tend to be of restricted taxonomic distribution (1 ). Such metabolites have an extensive history of use as therapeutic agents (2 ,3 ). The most common plant secondary metabolites occur in the following groups: alkaloids, anthraquinones, coumarins, essential oils (lower terpenoids and phenylpropanoids), flavonoids, steroids, and terpenoids (cardenolides, diterpenoids, iridoids, monoterpenoids, sesquiterpenoids [including sesquiterpene lactones], and triterpenoids) (4 ).