Hokkaido University, Hakodate, Japan
Oceans provide enormous and diverse habitats for marine life. The distinct feature of marine life is the domination of invertebrates, which account for more than 95% of marine animals. Most marine invertebrates are sessile and soft-bodied and lack obvious physical defenses. Instead, they have evolved to defend by chemical means against predation and overgrowth by other fouling organisms. In fact, their secondary metabolites have unusual structural features and potent biologic activities, many of which are not found in terrestrial natural products. This review focuses on bioactive metabolites isolated mainly from marine invertebrates with a special emphasis on the uniqueness of marine natural products.
The world's oceans cover more than 70% of the earth's surface and represent greater than 95% of the biosphere. Species ranging from 3 to 100 million are estimated to inhabit in the oceans. All but 1 of the 35 principal phyla in the animal kingdom are represented in aquatic environments; 8 phyla are exclusively aquatic. Most of them are sessile and soft-bodied organisms, most of which have evolved by chemical means to defend against predators and overgrowth by competing species. As expected, a variety of bioactive metabolites were found in marine invertebrates (see a series of reviews on marine natural products published in Natural Product Reports since 1984).
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