Sarcanolides C–E: three new lindenane sesquiterpenoid dimers with anti-inflammatory activities from Sarcandra glabra

Three new lindenane-type sesquiterpenoid dimers, sarcanolides C-E (1-3), were isolated from the roots of Sarcandra glabra. Sarcanolide C (1) possesses a unique decacyclic scaffold with an unusual orthoformate unit. The structures of 1-3 were determined through extensive spectroscopic analysis, while their absolute configurations were determined by comparison of calculated and experimental electronic circular dichroism (ECD) spectra. Compounds 1-3 were evaluated for their inhibitory activity against LPS-induced nitric oxide (NO) production in RAW264.7 macrophages. All the isolates displayed a moderate inhibitory effect against NO production with IC50 values in the range of 13.4-17.2 mu M, comparable to that of the positive control L-NMMA.