Theionbrunonines A and B: Dimeric Vobasine Alkaloids Tethered by a Thioether Bridge from <i>Mostuea brunonis</i>

Theionbrunonines A and B (<b>1</b> and <b>2</b>), the first examples of monoterpene bisindole alkaloids linked by a thioether bridge, were isolated from the stems of <i>Mostuea brunonis</i>, guided by a molecular networking-based dereplication strategy. Their structures were elucidated by a combination of spectroscopic data and ECD calculations. A plausible biosynthetic pathway for <b>1</b> and <b>2</b> was postulated. Theionbrunonines A and B (<b>1</b> and <b>2</b>) showed moderate antiplasmodial activities in the micromolar range against the strain FcB1 of <i>Plasmodium falciparum</i> and no cytotoxic activity against the MRC-5 cell line at 20 μM.