Anti-MRSA Dimeric and Brominated Phenyltetracenoids Produced by Streptomyces morookaense SC1169

Eleven new phenyltetracenoid polyketides, streptovertimycins U ( ) and V ( ), 14-bromo-streptovertidione ( ), streptovertimycins W-Y ( - ), and streptovertimycins Z -Z ( - , together with the known congeners fasamycins R ( ) and S ( ) and accramycins A ( ) and B ( ), were isolated from the NaBr-supplemented rice-grown cultures of SC1169. Their structures were elucidated by extensive spectroscopic analysis, single-crystal X-ray diffraction analysis, and theoretical computations of ECD spectra. Compounds and are methylene-bridged dimers of accramycin A, and compounds and - are brominated fasamycin congeners. Compounds and - exhibited activity against the drug-resistant bacteria MRSA and VRE (MIC = 0.6-5.0 μg/mL), and the dimer displayed activity against MRSA (MIC = 2.5 μg/mL). Compounds - showed cytotoxicity against the human carcinoma A549, HeLa, HepG2, and MCF-7 cells in the IC range between 1.7 and 9.2 μM.