Natural Organohalogen Compounds
Over the past decade, marine natural products chemists have demonstrated that marine organisms produce a wide variety of halogenated natural products. The halogenated natural products range in size from simple halomethanes to relatively large and complex
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Introduction
Over the past decade, marine natural products chemists have demonstrated that marine organisms produce a wide variety of halogenated natural products. The halogenated natural products range in size from simple halomethanes to relatively large and complex toxins. The principal sources of halogenated natural products are marine bacteria, marine algae and sponges, with smaller contributions from other marine invertebrates. Despite their importance in medicine, the halogenated antibiotics such as aureomycin and griseofulvin, which are manufactured by fermentation processes involving terrestrial microorganisms, have not been included as natural organohalogen compounds. This review of halogenated marine natural products will emphasize the major structural types of chemicals encountered, their chemotaxonomic relationships and, wherever possible, their potential environmental impact. Although there has been little research in these areas, the biosynthesis of halogenated organic compounds in marine organisms and the fate of halogenated marine natural products in seawater will be discussed briefly. Since it would be unrealistic to review every known halogenated marine natural product, I have selected representative examples from among groups of chemically similar compounds. Marine Bacteria
Several species or strains of marine bacteria have been shown to contain brominated pyrrole derivatives. In 1966, Burkholder et al. [1] showed that the antimicrobial agent produced by the marine bacterium Pseudomonas bromoutilis was a highly brominated pyrrole derivative J. The same pyrrole 1 was O. Hutzinger, The Natural Environment and the Biogeochemical Cycles © Springer-Verlag Berlin Heidelberg 1980
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subsequently found in four other antibiotic-producing strains of marine bacteria, including Chromobacterium sp. [2], which also contained tetrabromopyrrole 2 and hexabromobipyrrole 3. It is important to note that these halogenated bacterial metabolites were isolated because they possessed antimicrobial properties and not as a result of a systematic chemical investigation
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of marine bacteria. The production of antimicrobial compounds by marine bacteria is thought to provide a competitive advantage to the producing organism. However, when Chromobacterium sp. was grown in an enriched culture medium, sufficient amounts of the antibiotic pyrrole 1 were released into the medium to cause autotoxicity. This provides one simple illustration of the fact that the enriched culture medium required to grow a sufficient quantity of bacterial cells for chemical studies differs so considerably from the natural conditions found in the open ocean, on the surface of particles, or in the sediments, that we may never be able to determine the importance of marine bacteria in the production of halogenated natural products. Marine Algae
Considering the importance of the phytoplankton in the marine ecosystem, surprisingly little is known about the
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