Anthecularin: A Novel Sesquiterpene Lactone from <i>Anthemis auriculata</i> with Antiprotozoal Activity

Anthecularin (1), a minor sesquiterpene lactone with a novel ring system was isolated from Greek Anthemis auriculata (Asteraceae). Its structure was elucidated by means of NMR, HRMS, and X-ray crystallography. Anthecularin showed antitrypanosomal (IC50 = 10.1 μg/mL) and antiplasmodial activity (IC50 = 23.3 μg/mL) and inhibited two key enzymes of the plasmodial type II fatty acid biosynthesis pathway, PfFabI and PfFabG (IC50 values = 14 and 28.3 μg/mL, respectively). A probable biogenesis of 1 is also proposed and discussed.