ABSTRACT
The marine environment, with its enormous wealth of biological and chemical diversity, is unique in terms of the specic composition in both organic and inorganic substances present. Sessile marine invertebrates such as sponges, bryozoans, and tunicates, which mostly lack morphological defense structures, are producing a wide range of secondary metabolites, some of which provide a chemical defense function to the organism. These compounds have diverse and unusual structures which generally differ greatly to terrestrial natural products, with their exact function within the organism not always known. Due to their structural novelty, intricate carbon skeletons, and the ease at which the human body accepts these molecules with minimal manipulation, marine natural products are an important source of compounds that have had a crucial role in identifying novel chemical entities with useful drug properties (Cragg et al. 2006).
