Anti-MRSA Dimeric and Brominated Phenyltetracenoids Produced by 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.