Arsenal for survival: secondary plant products

The rise and fall over the first fifty years of plant chemosystematics, emp loying secondary products, is outlined here. The retention of some degree o f activity in this field is recommended, especially with the flavonoids tha t are of universal occurrence. This is not only to further refine systems o f plant classification below the family level, but also to map the still la rgely uncharted territory of bioactive metabolites in plants. Almost every plant species has a unique collection of secondary constituents distributed throughout its tissues, a proportion of which is likely to respond positiv ely to an appropriate medical bioassay. The success of the chemosystematic approach to the search for a renewable source of taxol, the anti-cancer dru g from Taxus brevifolia, is described.