Sesquiterpene lactones from Inula falconeri, a plant endemic to the Himalayas, as potential anti-inflammatory agents

► A series of sesquiterpene lactones were isolated from I. falconeri. ► Structures mainly belonged to guaiane, pseudoguaiane, and xanthane skeletons. ► 4, 11, 24, and 31 presented more potent nitric oxide inhibition than aminoguanidine. ► A preliminary structure-activity relationship was established.