Abstract
Six new sesquiterpene lactones were isolated from Eupatorium semialatum (Asteraceae). Their structures were elucidated as esters of the eudesmanolides 8ß-hydroxyreynosin (1 and 2), 8ß-hydroxybalchanin (3 and 4) and 8ß-hydroxymagnolialide (5 and 6) with the isomeric 4-hydroxy-5-(5-hydroxytigloyloxy)tiglic acid (1, 3 and 5) and 5-hydroxy-4-(5-hydroxytigloyloxy)tiglic acid (2, 4 and 6), respectively. The chemotaxonomic importance of these findings is discussed.