Pseudoverticin, a novel benzoquinone-derived ansamycin antibiotic obtained as new cell cycle inhibitor from Streptomyces pseudoverticillus YN17707

Pseudoverticin (1), a novel benzoquinone-derived ansamycin antibiotic showing cell cycle inhibitory activity, was isolated from the fermentation broth of Streptomyces pseudoverticillus YN17707 together with the known ansamycin antibiotic geldanamycin (2) through a bioassay-guided separation procedure. The structure of 1 was elucidated by spectroscopic methods, being characterized by an ansa bridge the same as that in 2 and a novel benzoquinone-derived moiety. Pseudoverticin (1) arrested the cell cycle of tsFT210 cells at the G0/G1 phase with the MIC value of 2.5 μM.