Oxoprothracarcin, a novel pyrrolo[1,4]benzodiazepine antibiotic from marine Streptomyces sp. M10946.

A novel pyrrolo[1,4]benzodiazepine antibiotic, designated oxoprothracarcin (3), was isolated from the marine strain Streptomyces sp. M10946 along with three known secondary metabolites, cyclo(D)-Pro-(D)-Val (1), cyclo(D)-Pro-(D)-Leu (2), and limazepine A (4). The chemical structures of these substances were elucidated by spectroscopic analyses, including 1D- and 2D-NMR and ESI-MS. Antitumor and antibacterial assays indicated that compounds 1-4 weakly inhibit the growth of MDA-MB-231 and A549 cells. The isolation of compound 3 with a high yield (36 mg/10 L) indicated that this marine S. sp. M10946 may provide new lead compounds for structural modification and drug screening.