New sesquiterpenic acids from Inula wissmanniana.

Eight new (1-8) and two known (9 and 10) sesquiterpenic acids featuring α-methylene-γ-carboxyl units were isolated from the whole plants of Inula wissmanniana, along with two new germacranolides (11 and 12). Their structures were elucidated based on detailed spectroscopic analysis, including HRESIMS, 1D and 2D NMR, and X-ray crystallography. Notably, the skeleton of 1 was firstly discovered from nature, while that of 2 was discovered for the second time. All the compounds were evaluated for their inhibition against LPS-induced nitric oxide (NO) production in RAW264.7 macrophages. Compound 11 exhibited the strongest activity with the IC50 value of 1.04 μM.