Sesquiterpenoids from the roots of Aucklandia costus and their anti-inflammatory activities.

Five undescribed sesquiterpenoid dimers, aucklandiolides A-E (1-5), one new sesquiterpenoid glycoside, β-cyclocostunolide-15-β-D-glucopyranoside (6), and seventeen known analogues (7-23) were isolated from the roots of Aucklandia costus. Their structures were elucidated by comprehensive HRESIMS and NMR spectroscopic data analysis, and their configurations were confirmed by the computational calculations of ECD and NMR chemical shifts. Aucklandiolides A and B are the first examples of dimeric sesquiterpenoids with a unique 6/6/6/5/6/6 ring system originated from a proposed Diels-Alder cycloaddition between two eudesmane sesquiterpenoids. Besides, compounds 9-11, 20, and 22 showed significant inhibition of nitric oxide production in LPS-stimulated RAW 264.7 cells at a concentration of 20 μM.