New sesquiterpenic acids from Inula wissmanniana

Abstract 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 IC 50 value of 1.04 μM.