LAUSR

A new antibiotic complex of six aureolic acids was isolated from the marine sediment-associated strain Streptomyces sp. KMM 9048. Four of the compounds (3–6) were found to be similar but not identical to the known chromomycins A2, A3, demethyl chromomycin A3 and A4. The two remaining compounds, A2–1 (1) and A3–1 (2), were established as novel chromomycin analogs, which did not contain sugar B. Spectroscopic methods including 1D and 2D NMR, and HRMS and MS/MS were applied for structure elucidation. Compounds 1-5 showed strong antimicrobial activity against Gram-positive indicatory bacteria Enterococcus faecium, Staphylococcus aureus, S. epidermidis, and Bacillus subtilis. Antitumor assay indicated that all tested compounds, in different manners, inhibited colony formation of RPMI-7951 and SK-Mel-28 cancer cells. This is the first study reporting the inhibitory effects of chromomycin analogs 1–5 on the colony formation of the investigated cancer cell lines. Compound 3, in a concentration of 5 nM, inhibited colony formation of RPMI-7951 and SK-Mel-28 cells by 82 % and 72 %, respectively. Our finding indicated that, of the compounds tested, 3 and 4 are promising anticancer and antimicrobial agents.