UCH9, a New Antitumor Antibiotic Produced by Streptomyces: I. Producing Organism, Fermentation, Isolation and Biological Activities

We developed a microbial prescreen using Bacillus stearothermophilus NUB3620 and bacteriophage TP-68 to detect potential antitumor compounds acting on DNA or topoisomerases. During the course of screening microbial cultures for their antibacteriophage activities, we found that Streptomyces sp. isolated from a soil sample collected in Iwakuni city, Yamaguchi prefecture, Japan, produced a new antitumor antibiotic, UCH9. UCH9 was isolated from culture broth by a combination of EtOAc extraction and column chromatography. UCH9 has a new structure related to the antitumor antibiotic chromomycins. It exhibited antimicrobial activity against Gram-positive organisms. UCH9 also showed cytotoxic activity against HeLa S3 cells with an IC50 value of 13nM and exhibited antitumor activity in vivo against mouse leukemia P388.