LC-MS guided isolation of gracilistones A and B, a pair of diastereomeric sesquiterpenoids with an unusual tetrahydrofuran-fused tricyclic skeleton from Acanthopanax gracilistylus and their potential anti-inflammatory activities

Gracilistones A ( 1 ) and B ( 2 ), two new eudesmane-type sesquiterpenoids with an unusual tetrahydrofuran-fused 6/6/5 tricyclic ring system, were obtained from Acanthopanax gracilistylus under the guidance of LC-MS investigation. Their structures and absolute configurations were assigned by extensive spectroscopic analyses and quantum calculation methods. Compounds 1 and 2 showed potent inhibitory activity against LPS-induced nitric oxide production in RAW 264.7 macrophages, compared with the positive control L-NMMA. In addition, compounds 1 and 2 were also evaluated for their antioxidant (DPPH • and ABTS •+ ) and xanthine oxidase (XO) inhibitory activities, and they exhibited weak inhibitory effects at 100 μM.