Two new sesquiterpenoids (1 and 2) and a new ent-pimarane type diterpenoid (3), together with eighteen known compounds (4-21), were isolated from the whole plants of Siegesbeckia pubescens. The structures of the new compounds were determined on the basis of 1D-, 2D NMR and HRESIMS data. All compounds were evaluated for their inhibitory effects on LPS-induced nitric oxide production in RAW 264.7 macrophages. Of these, highly oxygenated germacrane type sesquiterpenoids (1-2 and 13-14) showed significant inhibitory effects with IC50 values ranging from 3.9 to 16.8 μM.
Keywords: Asteraceae; Ent-pimarane diterpenoid; Germacrane sesquiterpenoid; Nitric oxide production inhibitor; Siegesbeckia pubescens.
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