Two new sesquiterpenes and six norsesquiterpenes from the solid culture of the edible mushroom Flammulina velutipes

One new sesquiterpene with a novel carbon skeleton, flammulinol A (1), one new isolactarane sesquiterpene and six isolactarane-related norsesquiterpenes, flammulinolides A–G (2–8), as well as sterpuric acid, were isolated from the solid culture of Flammulina velutipes. The structures of the new compounds were elucidated by spectroscopic methods. The absolute configuration of C-3 in 1 was determined via the circular dichroism data analysis based on the octane rule of cyclopentenone, whereas the absolute configurations of compounds 2, and 5–8 were assigned using the circular dichroism data of the Rh₂(OCOCF₃)₄] complex. Compounds 2, 3, and 7 showed strong cytotoxicity against KB cell line with the IC₅₀ of 3.9, 3.6, and 4.7 μM, respectively. Compound 4 showed strong cytotoxicity against Hela cell line with the IC₅₀ of 3.0 μM. The plausible biosynthetic pathway for 2–9 in F. velutipes was discussed.