Sesquiterpenoids isolated from the leaves of Aucklandia costus and their inhibitory effect on nitric oxide production.

Twelve previously undescribed sesquiterpenoids (named auckcostusnoids A-L, 1-12), together with eighteen known analogues (13-30), were isolated from the leaves of Aucklandia costus. The structures of compounds 1-12 were elucidated through comprehensive spectroscopic analyses, and their absolute configurations were established by a combination of NMR and electronic circular dichroism (ECD) calculations. Structurally, all isolated sesquiterpenoids were classified into bisabolane-type (1-8 and 13) and eudesmane-type (9-12 and 14-30) skeletons, among which the bisabolane-type sesquiterpenoids are reported from A. costus for the first time. Notably, compound 11 represents a rare 12,13-dinoreudesman sesquiterpenoid. All isolates were subsequently evaluated for their inhibitory effects on LPS-induced nitric oxide production in RAW264.7 macrophages. Compounds 10 and 27 exhibited moderate inhibitory activity, with IC50 values of 29.47 ± 1.47 and 38.97 ± 0.76 μM, respectively. Whereas compounds 9, 11, and 13 showed weak inhibitory effects, with inhibition rates of 38.70∼45.48% at a concentration of 40 μM.