Flavonoids from the stems of Ammopiptanthus nanus and their in vitro and in vivo anti-inflammatory activities.

Ammopiptanthus nanus (M. Pop.) Cheng f. (A. nanus) is known for its anti-rheumatoid arthritis effects in folk medicine. This study conducted an anti-inflammatory activity-guided exploration of A. nanus stem crude extract. Twenty-five flavonoids, including five isoflavonoids with novel structures, were isolated and identified. Their structures were determined by using HRESIMS, NMR, IR, UV, optical rotation data and X-ray crystallography. Among them, compound 1 features a unique dihydropyran skeleton connected to the A-ring of the isoflavone. The obtained flavonoids were screened for their anti-inflammatory effects in LPS-induced RAW 264.7 cells. Notably, lupiwighteone (14) with an IC50 value of 22.76 ± 3.37 μM, showed the most potent inhibitory effect, which could suppress the release of NO by inhibiting the expression of iNOS protein. Further in vivo experiment results revealed that lupiwighteone (14) might improve the survival rates in mice subjected to LPS-induced septic shock and selectively suppress the release of IL-1β to inhibit NLRP3 inflammasome.