Lanostane-type triterpenoids from the fungus <i>Inonotus obliquus</i>

Triterpenoids of the lanostane type are the primary characteristic compounds isolated from <i>Inonotus obliquus</i>. Phytochemical investigations on the EtOAc extract of the fungus led to the isolation of three new lanostane-type triterpenoids (compounds <b>1-3</b>) and 18 known derivatives. Their structures were determined from spectroscopic data, including NMR and HR-ESI-MS data, and quantum chemical calculations. The isolated lanostane-type triterpenoids exhibit a range of structures, characterised by the different C-17 side chains such as a 21, 24-cyclopentanol moiety, a γ-lactone ring, and a tetrahydrofuran ring. The ¹³C chemical shifts variation for both C-21 and C-24 in 21, 24-cyclolanostanes were examined and summarised, offering a useful diagnostic tool to determine the relative configuration of the 21, 24-cyclopentanol moiety in the four types of 21, 24-cyclolanostanes.