Pilot-Scale Libraries of Marine Cyanobacterial Natural Products

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DESCRIPTION (provided by applicant): Cyanobacteria are among the most ancient organisms on Earth and their ubiquitous presence to this day in terrestrial, freshwater and marine environments is indication for their success in competitive situations. Many cyanobacteria produce an array of different secondary metabolites, and it is estimated that some of these life forms devote up to 10% of their genome to secondary metabolism, presumably for defense purposes to gain competitive advantages. Cyanobacterial secondary metabolites (natural products) isolated so far have only been tested in very few assays, yet hit rates in cytotoxicity or target-based assays towards anticancer drug discovery have been quite high. Yet relatively little explored, secondary metabolites produced by marine cyanobacteria are privileged structures that are already well-optimized to interact with biological targets. The overall goal of this proposed research is to isolate known and to discover new natural products from benthic marine cyanobacteria that will possess unique structural features and will occupy biologically relevant chemical space not yet represented in the MLSMR. Furthermore, efforts will be undertaken to determine the best methods for culturing marine benthic cyanobacteria that optimize production of targeted compounds and also provide sustainable compound supply. First, "superproducing" cyanobacteria with proven rich secondary metabolite content will be re-collected from several locations in US waters in the Pacific and Florida and structurally diverse metabolites re-isolated and fully characterized. Second, we will determine the best methods for culturing marine benthic cyanobacteria that optimize production of targeted compounds, which also provides sustainable compound supply. Third, yet uncharacterized cyanobacteria will be collected from several locations in the western Pacific around Guam and in Florida. Extracts will be chromatographically fractionated and analyzed by NMR for the presence of secondary metabolites, i.e., peptides and peptide-polyketide hybrids. Compounds are purified by HPLC and structures elucidated by spectroscopic techniques, particularly NMR and mass spectrometry. PUBLIC HEALTH RELEVANCE: Marine cyanobacteria produce natural products which are structurally unique, biologically active, and have not been extensively tested for their activities against disease-relevant targets. These natural products will significantly enrich the diversity of the MLSMR.