New sesquiterpenes from Inula japonica Thunb. with their inhibitory activities against LPS-induced NO production in RAW264.7 macrophages

Twenty-two new sesquiterpenes were isolated from the aerial parts of Inula japonica Thunb., together with fifteen known ones. Their structures were determined by detailed spectroscopic analysis, X-ray diffraction studies, and modified Mosher method. All 37 compounds were evaluated for the inhibition of LPS-induced nitric oxide (NO) production in RAW264.7 macrophages, and most of isolates significantly inhibited the NO production with IC50 values in the range of 3.5–20 μM. Besides, results obtained in our studies provided a structure–activity relationship that would be used to design anti-inflammatory agents in the future.