Simocyclinones, a novel group of angucyclinone antibiotics, are produced by Streptomyces antibioticus Tü 6040. The compounds show antibacterial and antitumor properties. In submerged cultivation, the production of simocyclinones is strongly dependent on the carbon and nitrogen sources used in a chemically defined medium. Productivity of distinct components and diversity of simocyclinone compounds are influenced by the medium composition. Four series of simocyclinone compounds were detected by high-performance liquid chromatography (HPLC) diode array detector (DAD) and HPLC electrospray ionization (ESI) mass spectrometry (MS) analysis, isolated and the structures determined by nuclear magnetic resonance (NMR) techniques. Under optimized conditions, simocyclinone D8 was produced in an amount of 300 mg l(-1) and simocyclinone C4 in a concentration up to 50 mg l(-1).