Marine sponges, plant secondary metabolite

While secondary metabolites of plants and animals have been the subject of many chemical investigations, their associations and roles in their host organism are at times controversial this is particularly so, when insufficient observations exist. Nevertheless, natural products provide fruitful areas of research [69]. There is little doubt that chemical defense against predators is an important aspect of survival. In the marine environment, early observations of nudi-branch- sponge relationships were reported and those relating to isocyano compounds are summarized in Table 6. 

The relative contribution to the cup of natural products by marine and terrestrial organisms is outlined in Table 9.1. Column entries are the phylum, class or order, number of species, biogenetic class of metabolites produced, their bioactivity level, and a qualitative indication as to the average molecular complexity (Whitlock 1998). The latter property receives closer attention in Table 9.II for specific molecular skeletons. These data warrant several conclusions. First, unusual secondary metabolites on land derive mostly fi-om green plants and arthropods, while in the sea are the algae, sponges, cnidarians, bryozoans, and ascidians that give most. This is true no matter if the molecular skeleton, or the actual metabolite, or even the bioactivity, is examined. 

Clerodane-type secondary metabolites have been found in several hundreds of plant species from various families and in organisms from other taxonomic groups, such as fungi, bacteria, and marine sponges.8 Especially, various genera from the plant families Labiatae and Verbenaceae have been identified as rich sources of clerodanes with antifeedant activity.63 Species of the genus Scutellaria (Labiatae) produces some of the most potent clerodane antifeedants known so far. 

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