Rupestonic acids B-G, NO inhibitory sesquiterpenoids from Artemisia rupestris

Six new guaiane sesquiterpenoids, rupestonic acids B-G (1-6), have been isolated from the whole plants of Artemisia rupestris together with six known compounds (7-12). The structures of the new isolates (1-6) were elucidated on the basis of extensive 1D and 2D NMR analysis, and the absolute configurations were established by electronic circular dichroism (ECD) in combination with density functional theory calculations. In in vitro bioassays, compounds 2 and 6 exhibited significant inhibitory effects on LPS-stimulated NO production in BV-2 microglial cells with IC50 values of 2.6 and 2.2 μM, respectively.