Bioactive Secondary Metabolites from Marine and Terrestrial Bacteria: Isoquinolinequinones, Bacterial Compounds with a Novel Pharmacophor

After a chemical and biological pre-screening of bacterial extracts, 17 Streptomycetes (including eleven terrestrial and six marine-derived strains) and ten North Sea bacteria (including five Roseobacter strains) were studied in detail. From the North Sea strains, 47 compounds were obtained, from which eleven are new secondary metabolites from bacteria. The eleven terrestrial Streptomycetes were found to produce 45 compounds, out of which ten natural products are reported here for the first time. From the marine Streptomycetes 25 compounds were isolated, five of which were new natural products. Altogether, 118 metabolites were isolated, including, 6 macrolides, 1 peptide, 13 quinones, 3 polyenes, and 2 isoquinolinequinones. Their structures were elucidated using spectroscopic methods, including HPLC-MS, MALDI-TOF, and NMR experiments. Biological activities were tested against bacteria, fungi, algae, saline shrimps, and nematodes.