Fluostatins I-K from the South China Sea-Derived Micromonospora rosaria SCSIO N160

The strain SCSIO N160 was isolated from a South China Sea sediment sample and was characterized as a Micromonospora rosaria species on the basis of its 16S rRNA gene sequence. Three new fluostatins, I-K (1-3), were isolated from the culture of M rosaria SCSIO N160, together with six known compounds, fluostatins C-F (4-7), rabelomycin (8), and phenanthroviridone (9). The structure of fluostatin D (5) was confirmed by an X-ray crystallographic study. The absolute configuration of 1 and 3 was assigned by electronic circular dichroism calculations. Compounds 8 and 9 exhibited good antimicrobial activities against Staphylococcus aureus ATCC 29213 with MIC values of 1.0 and 0.25 mu g/mL, respectively. Compound 9 also exhibited significant in vitro cytotoxic activities toward SF-268 (IC50 0.09 mu M) and MCF-7 (IC50 0.17 mu M).