Helenalin: Mechanism of Toxic Action

Several range plants, including Hymenoxys odorata (bitterweed) and Helenium microencephalum DC (smallhead sneezeweed) contain toxic principles believed to be the etiologic agents responsible for severe losses of grazing livestock1. Hymenoxon, a sesquiterpene lactone, has been isolated from Hymenoxys odorata and studies with laboratory animals have demonstrated that this compound elicits toxic effects which resemble those reported for field case studies. Helenalin, a structurally related sesquiterpene lactone isolated from Helenium microencephalum DC, exhibits toxic properties which resemble those reported for hymenoxon and suggests that these compounds act via a common mechanism.