Chemical constituents from Inonotus obliquus and their antitumor activities.

Four new lanostane-type triterpenes (inonotusanes D-G, 1-4), including a 24,25,26,27-tetranorlanostane, together with 11 known compounds (5-15), including 7 lanostane derivatives, 2 steroids and 2 aromatic compounds, were isolated from the sclerotia of Inonotus obliquus. Their structures were elucidated by 1D and 2D NMR spectroscopy and HRMS. To our knowledge, 1 is the first 24,25,26,27-tetranorlanostane-type triterpenoid from fungus, and this is the first time that 31-member lanostane-type triterpenes, 5 and 6, have been isolated from the sclerotia of I. obliquus instead of from its submerged culture. 7 and 8 are also new isolates of this genus. Compounds 1, 8, 12 and 13 exhibited strong cytotoxicity against the 4T1 (mouse breast cancer) cell line, with IC50 9.40, 7.79, 9.06 and 9.31 μM, respectively. 8, 12 and 13 also exhibited strong cytotoxicity against the the MCF-7 (human breast cancer) cell line, with IC50 8.35-9.01 μM.