Sesquiterpenes from Ainsliaea fragrans and their inhibitory activities against cyclooxygenases-1 and 2.

One new guaiane-type sesquiterpene glycoside, 2'-O-E-caffeoyl-8 alpha-hydroxy-11 alpha,13-dihydro-3 beta-O-beta-D-glucozaluzanin C (1), was isolated from the whole herb of Ainsliaea fragrans (Compositae), together with five known sesquiterpene lactones: 8 alpha-hydroxy-11 alpha,13-dihydro-3 beta-O-beta-D-glucozaluzanin C (2), 8 alpha-hydroxy-11 alpha,13-dihydrozaluzanin C (3), 3 alpha-hydroxy-11 beta,13-dihydro-8 alpha-O-beta-D-glucozaluzanin C (4), 3 beta-hydroxy-11 beta,13-dihydro-8 alpha-O-beta-D-glucozaluzanin C (5), 3 beta-O-beta-D-glucozaluzanin C (6). The structures of isolated compounds were established by means of 1D and 2D NMR spectroscopy and chemical methods. All isolates obtained in the present study were evaluated for their inhibitory effects against cyclooxygenases-1 and 2 in vitro, and the structure-activity relationships were also discussed.