Antibacterial and Cytotoxic Phenyltetracenoid Polyketides from Streptomyces morookaense

Formicapyridine-type racemates, streptovertidines A (1) and B (2), a 7,24-seco-fasamycin, streptovertidione (3), and the fasamycin-type streptovertimycins I–T (4–15), together with 13 known fasamycin congeners (16–28), were isolated from soil-derived Streptomyces morookaense SC1169. Their structures were elucidated by extensive spectroscopic analysis and theoretical computations of ECD spectra. The fasamycin-type compounds 5, 8–12, 14, and 15 exhibited activity against the drug-resistant bacteria MRSA and VRE (MIC: 1.25–10.0 μg/mL). All isolates, except 3, 4, 10, and 24, displayed cytotoxicity against at least one of the human carcinoma A549, HeLa, HepG2, and MCF-7 cells (IC50 3 to 1 were carried out and supported that the pyridine ring formation in formicapyridines proceeds nonenzymatically via 1,5-dicarbonyl condensation with ammonia.