Sesquiterpenes from the rhizomes of Alpinia japonica and their inhibitory effects on nitric oxide production.

A novel norsesquiterpene (1), three new bisabolenes sesquiterpenes (2-4), along with 7 known compounds (5-11), were isolated from the rhizomes of Alpinia japonica. The structures of the new compounds were elucidated by analysis of spectroscopic data. The absolute configuration of C-1 in 3 was deduced via the circular dichroism data of the in situ formed [Rh2(OCOCF3)4] complexes. Inhibitory effects of the isolates on nitric oxide production in lipopolysaccaride-activated RAW264.7 macrophages were evaluated. Compound 6 showed significant inhibitory activity with IC50 value of 5.3 μΜ, and compounds 1, 3, 5 and 7-10 exhibited moderate inhibitory activities with IC50 values between 24.5 and 46.3 μM.