Fluostatins I–K from the South China Sea-Derived <i>Micromonospora rosaria</i> SCSIO N160

Abstract

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