Five New Meroterpenoids from the Fruiting Bodies of the Basidiomycete Clitocybe clavipes with Cytotoxic Activity

Five new meroterpenoids, clavipols A–B (1–2) with a 12-membered ether ring and clavilactones G–I (3–5) having a 10-membered carbocycle connected to a hydroquinone and an α,β-epoxy/unsaturated lactone, were obtained from the fruiting bodies of the basidiomycete Clitocybe clavipes. Their structures were determined by comprehensive analysis of their spectroscopic data, and the absolute configuration of 1 was established by quantum chemical calculations of electronic circular dichroism (ECD). All the isolated compounds (1–5) were tested for their cytotoxic activity against three human tumor cell lines (Hela, SGC-7901, and SHG-44) in vitro after treatment for 48 h. Compound 4 exhibited moderate cytotoxic activity against Hela and SGC-7901 tumor cell lines, with IC(50) values of 23.5 and 14.5 µM, respectively.