Discovery of Antimicrobial Oligoindoles from a Cold-Seep-Derived Halomonas Strain

Mining bioactive secondary metabolites from microorganisms originating from deep-sea cold seep holds significant potential for discovering novel drug lead compounds. In this study, three known indole derivatives (<b>1</b>-<b>3</b>) were isolated from cold-seep-derived <i>Halomonas meridiana</i> OUCLQ22-B7. Subsequently, two-new indole dimers, meribisindole A (<b>4</b>) and meribisindole B (<b>5</b>), with nine known metabolites (<b>6</b>-<b>14</b>) were obtained via indole precursor feeding strategy. The structure of these compounds was elucidated via a combination of spectroscopic methods and circular dichroism (CD) measurement. Antimicrobial assays revealed that compounds <b>4</b>, <b>7</b> and <b>8</b> exhibited potent inhibitory activity against <i>Fusarium oxysporum</i> CICC 41029 with minimal inhibitory concentrations (MICs) of 0.39-12.5 μg/mL, and compound <b>11</b> showed significant growth inhibition against <i>Staphylococcus aureus</i> CCARM 3090 with MIC value at 0.098 μg/mL.