Sesquiterpenoids from Inula racemosa Hook. f. inhibit nitric oxide production.

A novel trinorsesquiterpene (1), three new (2-4), and 10 known sesquiterpenes were isolated from the roots of Inula racemosa Hook. f. The structures and absolute configurations of the new sesquiterpenes were elucidated by extensive spectroscopic and computational methods. All compounds were evaluated for their inhibition of LPS-induced nitric oxide production in RAW264.7 macrophages, and the results indicated that compounds 9, 12, and 13 moderately inhibited nitric oxide production with IC₅₀ values of 7.39 ± 0.36, 6.35 ± 0.26, and 5.39 ± 0.18 µM, respectively. © Georg Thieme Verlag KG Stuttgart · New York.