Lanostane-type triterpenoids from the fungus Inonotus obliquus

Triterpenoids of the lanostane type are the primary characteristic compounds isolated from Inonotus obliquus. Phytochemical investigations on the EtOAc extract of the fungus led to the isolation of three new lanostane-type triterpenoids (compounds 1-3) 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.