3. Chemical Defence in Marine Ecosystems

Summary

Nature has provided a broad arsenal of structurally diverse and pharmacologically active compounds that serve as highly effective drugs or lead structures for the development of novel drugs to combat a multitude of diseases. Traditionally, terrestrial organisms represent the richest source of natural drugs. Considering the fact that over 70% of the surface of the earth is covered by oceans that harbour a rich biodiversity, aspiration in marine bioprospecting as a viable counterpart for the discovery of bioactive compounds from the terrestrial environment seems justified. Interestingly, the majority of marine natural products involved in clinical or preclinical trials is produced by invertebrates, which is in contrast to compounds derived from the terrestrial environment where plants by far exceed animals with respect to the production of bioactive metabolites. The fact that bioactive metabolites are predominantly found in sessile or slow-moving marine organisms that lack physical defence structures thus appears to reflect the ecological importance of these compounds with respect to inter- as well as intraspecific interactions, for example predation, competition for space and fouling. Numerous natural products from marine invertebrates show striking structural similarities to known metabolites of microbial origin. This fact suggests that microorganisms such as bacteria and microalgae that often live associated with marine invertebrates are at least involved in the biosynthesis or are in fact the true sources of these respective metabolites in many cases.