Sesquiterpenoids with diverse carbon skeletons from the roots of Cichorium glandulosum and their anti-inflammatory activities

A total of thirteen sesquiterpenoids with diverse skeletons including four new sesquiterpenoids, glandulosines A − D (1–4), a new natural product, glandulosine E (5), and eight known sesquiterpene lactones (6–13) were isolated from the roots of Cichorium glandulosum Boiss. et Huet (Asteraceae). Their structures were determined by extensive spectroscopic experiments including NMR, electronic circular dichroism (ECD), calculated ECD, Rh2(OCOCF3)4-induced ECD, and single-crystal X-ray diffraction analysis, as well as chemical methods. This is the first report of the crystal structure of 11β,13-dihydrolactucin (11). Thirteen isolated sesquiterpenoids (1−13) were evaluated for their anti-inflammatory activities in vitro, and three guaiane sesquiterpene lactones, glandulosine E (5), scorzoside (9), and lactucin (10) showed moderate inhibitory activity against LPS-induced nitric oxide (NO) production in RAW 264.7 macrophages.