Ripromycin and other polycyclic macrolactams from Streptomyces sp Tu 6239: Taxonomy, fermentation, isolation and biological properties

Strain Tu 6239 was isolated from a soil sample collected in Brazil and determined as a new species of the genus Streptomyces. In the course of our HPLC-diode array screening program three metabolites were detected in the culture filtrate and mycelium extracts of strain Tu 6239. They were characterised as members of the macrolactam group, the new compound ripromycin (1), the previously described ikarugamycin (2) and a new derivative of it, ikarugamycin epoxide (3). They show antibiotic activities against Gram-positive bacteria and cytostatic effects to various human tumor cell lines.