Sesquiterpenoids from Tussilago farfara and their inhibitory effects on nitric oxide production.

Tussilagone (TSL) and its allied sesquiterpenoids were considered as the main active principles of the flower buds of Tussilago farfara, which has been widely used in China as an antitussive herbal medicine. Six new bisabolane-type sesquiterpenoids, tussfararins A-F (1-6), along with 12 known sesquiterpenoids, were isolated from the flower buds of T. farfara. Structures of the new compounds were elucidated by extensive spectroscopic analysis. The biological analysis showed that compounds 1, 3, 6, and 7 inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells with IC50 values of 13.6-24.4 µM.