Chemodiversity and the biological role of secondary metabolites, some thoughts for selecting plant material for drug development

Plants produce various defence compounds; some are constitutively expressed, while others are activated upon cell damage, or are produced after induction through exogenous signalcompounds. From the physiological role of the secondary metabolites in plants one can draw some conclusions about the chance of finding new biologically active compounds. In the search for biologically active compounds, particularly young tissues and seedlings seem to be interesting sources. Treatment of plant material with for example glycosidases may result in the generation of new compounds. Infected plant materials may be an additional source for different types of secondary metabolites, which may also be found in plant cell cultures after treatment with elicitors. Such compounds are particularly of interest for screening for antimicrobial and antitumor activity. Inducible pathways may also be the cause of considerable variation in different collections of plant material.