Introduction

First, there is a strong biological and ecological rationale for plants and marine invertebrates to produce novel bioactive secondary metabolites. The importance of plants and marine organisms as a source of novel compounds is probably related in large measure to the fact that they are not mobile, and hence must defend themselves by deterring or killing predators, whether insects, œsh, microorganisms, or animals. Plants and marine organisms have thus evolved a complex chemical defense system, which can involve the production of a large number of chemically diverse compounds. It has been proposed that all natural products have evolved to bind to speciœc receptors,1 and evidence for the advantage that the natural products give an organism over predators has been found in ecological studies in the marine environment related to predator deterrence.2 As far as microbial species are concerned, secondary metabolites from the prokaryota and also from certain phyla in the eukaryota are actually synthesized in a combinatorial manner.3 This is the case because the genes that are ultimately responsible for the chemical structures that are obtained from these microbes, plants, and marine invertebrates can frequently be “shufŸed” between taxa, and these shufŸed genes produce diverse secondary metabolites, some of which are of use to man.