Structure elucidation of a new triterpene from Inonotus obliquus.

Ethyl acetate (EtOAc) fraction of the Inonotus obliquus (Hymenochaetaceae) significantly inhibited nitric oxide production in lipopolysaccharide (LPS)-induced murine BV2 microglial cells. A new triterpene, characterized as inonotusol H (1), was isolated from the EtOAc fraction using the bioactivity-guided fractionation together with four known triterpenes, inotodiol (2), trametenolic acid (3), inonotsutriols A (4), and inonotusol A (5). Among them, Compounds 2-4 significantly reduced LPS-induced nitric oxide production to 4.5 ± 0.8%, 47.4 ± 4.4%, and 2.8 ± 1.7%, respectively, at a concentration of 30 μM.