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Instant insight: In from the cold
03 May 2007
Bill Baker from the University of South Florida, Tampa, US, extols the virtues of cold-water marine natural products and considers their future prospects
The words coral and sponge might conjure up pleasant thoughts of warm tropical waters and colourful fishes. The organic chemists among us may think of terpenes and polyketides, while pharmacologists might reflect on anti-inflammatory or anti-cancer agents. That these disparate images are not incongruous is testament to the growing role of marine organisms as sources of biomedically important chemical diversity. Yet much remains to be discovered. With more than 70 per cent of the earth covered by oceans, marine natural products represent only 10 per cent of natural products described to date.
Diving under ice: not your routine scuba trip
© Norbert Wu
Nonetheless, accumulating biological and chemical research, points to a rich cold-water flora and fauna and an active ecology, as dependant upon chemical defenses as many lower latitude habitats. Among bioactivity-producing organisms, sponge biodiversity in Antarctica is as high as that found at temperate latitudes, and deep sea microbial fauna are among the most diverse known. Recent studies have also shown cold-water invertebrate-associated microbe communities are robust. From the chemical laboratory, unique structural motifs have emerged, as have biological activity profiles that have caught the attention of the pharmaceutical industry. Variolin B, for example, is a structurally unique cyclin-dependent kinase inhibitor from an Antarctic sponge that is in clinical development as an anti-cancer drug. Meridianins and palmerolides derive from Antarctic tunicates and have advanced in synthetic and pharmacological studies. Meridianins have a similar activity to variolin B, while palmerolide A, a potent inhibitor of the enzyme vacuolar-ATPase, targets melanoma. In addition to cytotoxicity, cold-water natural products are known to act as antibiotic, antiviral, antifouling, hemolytic, serotonergic, and ion channel modulating agents, as well as displaying inhibitory activity toward a number of specific enzymes.
Antarctic sponges supply variolin B
So the cold-water chemical diversity story has yet to unfold, but the case is compelling. While sampling will always be more challenging in these environments, there is little doubt that chemical rewards of cold-water biodiversity await the intrepid bioprospector.
Read Bill Bakers review on 'Cold-water marine natural products' in an upcoming issue of Natural Product Reports.