Sesquiterpenoids from Inula lineariifolia inhibit nitric oxide production

Fourteen sesquiterpenoids including six new analogues (1-6) were isolated from the aerial parts of Inula lineariifolia.. The structures of the new sesquiterpenoids were determined by spectroscopic data analysis, and the structures of 1 and 6 were confirmed by single-crystal X-ray diffraction data and the modified Mosher method. All 14 compounds were examined for the inhibition of LPS-induced nitric oxide production in RAW264.7 macrophages. Compounds 6, 13, and 14 were found to inhibit nitric oxide production potently, with IC(50) values of 0.11, 0.25, and 0.10 microM, respectively.