Sesquiterpenes from Rhododendron nivale and Their Anti-Inflammatory Activity.

Two new germacrane sesquiterpenes, named nivalenoids A and B (1 and 2), along with four known sesquiterpenes (3-6), were isolated from the Rhododendron nivale. The structures of compounds 1 and 2 were elucidated by integrating spectroscopic analyses, including NMR, UV, IR, as well as HR-MS data. Anti-inflammatory activity by inhibiting lipopolysaccharide (LPS)-induced NO production in RAW 264.7 cells revealed that compared with the positive control dexamethasone (IC 50 =2.50 μM), compounds 1 and 2 showed mild anti-inflammatory activity, with IC 50 value of 27.55 μM and 53.26 μM, respectively.