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.

Four new gamma-pyrones, nocapyrones A-D (1-4), were isolated from an organic extract of the Nocardiopsis strain HB383, which was isolated from the marine sponge Halichondria panicea. These are the first gamma-pyrones reported from a Nocardiopsis strain. The structures were elucidated on the basis of one- and two-dimensional NMR experiments and supported by HPLC-UV/MS and HRESIMS analyses. The biosynthesis of nocapyrone A was investigated by feeding experiments with (13)C-labeled compounds. In addition, one diketopiperazine, which was only known as a synthetic compound before, was isolated. The bioactivies of 1, 2, and the diketopiperazine were evaluated in a panel of assays.

Dereplicated novel actinomycetes from neglected habitats provide high quality biological material for screening programs designed to detect novel bioactive secondary metabolites. 2 Such organisms include neutrotolerant acidophilic streptomycetes which grow from pH 4.5 to 7.5, with an optimum between pH 5.0 and 5.5. 3 Members of this group were isolated from a hay meadow soil taken from Cockle Park Experimental Farm in Northumberland, UK. The isolates were grown as submerged cultures in complex media, and extracts from the culture filtrates and mycelia included in our HPLC-diode array screening program to detect novel secondary metabolites by means of an in-house HPLC-UV-Vis database, which contains approximately 950 natural products, mainly antibiotics. 4 Strain BK 190 was of interest because of the presence of three prominent peaks in the HPLC profile of a culture filtrate extract. The strain was assigned to the genus Streptomyces by its morphological and chemotaxonomic properties. 5 Strain BK 190 formed an extensively branched substrate mycelium, a grey aerial spore mass and aerial hyphae, which differentiated into spiral chains of smooth-surfaced spores on oatmeal agar, contained LL-diaminopimelic acid, galactose, glucose and xylose as major sugars, N-acetylated muramic acid, predominant amounts of hexa-and octa-hydrogenated menaquinones with nine isoprene units, and produced iso-and anteiso-branched fatty acids with C 15:0 and iso-C 16:0 as major components. The temperature and pH ranges for growth were 10-35 1C and pH 4.0-8.0, respectively. Phylogenetic analyses showed that the organism was most closely related to the type strain of Streptomyces sanglieri; the two organisms shared a 16S rRNA similarity of 99.9%, a value that corresponds to a single nucleotide difference at 1434 locations.The metabolite with retention time of 12.3 min in our standardized reversed-phase gradient elution profile was identified by HPLC-diode array and HPLC-ESI-MS analysis to be elaiomycin (1), an azoxy antibiotic that was first isolated from Streptomyces hepaticus and found to strongly inhibit the growth of Mycobacterium tuberculosis. 6 Two further prominent peaks, elaiomycin B (2) with a retention time of 16.4 min, and elaiomycin C (3) with a retention time of 17.2 min showed characteristic UV-vis spectra that differed from those of all of the reference compounds stored in the database. A significant production of 1-3 was observed in oatmeal medium in the 100 ml shake flask scale, which was reproducible in a scale up to a 20-liter fermentor. Strain BK 190 reached a maximal biomass of 12 volume (%) at a cultivation time of 96 h and this correlated with the highest production of elaiomycins, which reached yields of 24 mg l À1 elaiomycin (1), 15 mg l À1 elaiomycin B (2) and 9.5 mg l À1 elaiomycin C (3) in the culture filtrate, and 15 mg l À1 of 2 and 12 mg l À1 of 3 in the mycelium, respectively. Compounds 1-3 were isolated from the culture filtrate by separation on an Amberlite XAD-16 column (Rohm and Haas Deutschland, Frankfurt...