A new benz[a]anthracene derivative called mayamycin (1) was identified in cultures of Streptomyces sp. strain HB202, which was isolated from the marine sponge Halichondria panicea and selected because of its profound antibiotic activity. The ability to produce aromatic polyketides was indicated by genetic analyses, demonstrating the presence of a type II polyketide synthase. The production of mayamycin (1) was induced by variation of the culture conditions. The structure of 1 was elucidated by HPLC-UV/MS and NMR spectroscopy. Mayamycin (1) exhibited potent cytotoxic activity against eight human cancer cell lines and showed activity against several bacteria including antibiotic-resistant strains.

New bioactive secondary metabolites, called abenquines, were found in the fermentation broth of Streptomyces sp. strain DB634, which was isolated from the soils of the Chilean highland of the Atacama Desert. They are composed of an amino acid linked to an N-acetyl-aminobenzoquinone. Isolation of the abenquines (1-4), their structure elucidation by NMR analysis and MS, as well as the kinetics of their production are presented. The abenquines show inhibitory activity against bacteria, dermatophytic fungi and phosphodiesterase type 4b. The amino acid attached to the quinone is relevant to the enzyme inhibitory activity. The Journal of Antibiotics (2011) INTRODUCTIONThe Northern Chilean highlands of the Atacama Desert comprise a number of extreme habitats, including permanent arid soils exposed to very high UV irradiation and strong fluctuations in temperature, various types of salt lakes differing in salinity and mineral salts composition and also geothermal-driven hot springs and geysers. These habitats make this area extraordinarily interesting for studies of microbial communities adapted to extreme environmental conditions. Previous studies have shown that salt lakes of this area harbor unique communities of anoxygenic phototrophic bacteria 1 and cyanobacteria. 2 Recently, we have isolated a number of actinobacteria from arid soils of the Atacama Desert and characterized them in regard to their potential to synthesize secondary metabolites. In this study, we present the secondary metabolite profile of one of the isolated Streptomyces strains.

Bioactive compounds were detected in crude extracts of the fungus, Calcarisporium sp. KF525, which was isolated from German Wadden Sea water samples. Purification of the metabolites from the extracts yielded the five known polyesters, 15G256α, α-2, β, β-2 and π (1–5), and five new derivatives thereof, named calcarides A–E (6–10). The chemical structures of the isolated compounds were elucidated on the basis of one- and two-dimensional NMR spectroscopy supported by UV and HRESIMS data. The compounds exhibited inhibitory activities against Staphylococcus epidermidis, Xanthomonas campestris and Propionibacterium acnes. As the antibacterial activities were highly specific with regard to compound and test strain, a tight structure-activity relationship is assumed.

Geranylphenazinediol (1), a new phenazine natural product, was produced by the Streptomyces sp. strain LB173, which was isolated from a marine sediment sample. The structure was established by analysis of NMR and MS data. 1 inhibited the enzyme acetylcholinesterase in the low micromolar range and showed weak antibacterial activity. In order to get a more detailed picture of the activity profile of 1, its inhibitory potential was compared to that of related structures.

Microbial studies of the Mediterranean sponge Tethya aurantium led to the isolation of the fungus Bartalinia robillardoides strain LF550. The strain produced a number of secondary metabolites belonging to the chloroazaphilones. This is the first report on the isolation of chloroazaphilones of a fungal strain belonging to the genus Bartalinia. Besides some known compounds (helicusin A (1) and deacetylsclerotiorin (2)), three new chloroazaphilones (helicusin E (3); isochromophilone X (4) and isochromophilone XI (5)) and one new pentaketide (bartanolide (6)) were isolated. The structure elucidations were based on spectroscopic analyses. All isolated compounds revealed different biological activity spectra against a test panel of four bacteria: three fungi; two tumor cell lines and two enzymes.