Two new bicyclic lactones, myrotheciumones A (1) and B (2) which possessed a rare ring-fusion system were isolated from Myrothecium roridum (M. roridum), an endophytic fungus of the medicinal herb plant Ajuga decumbens (A. decumbens) via an in vitro cytotoxicity assay. Structures were deduced from 1D and 2D NMR (Nuclear magnetic resonance) data. Myrotheciumone A’s in vitro cytotoxicity and apoptotic activity were evaluated and myrotheciumone A was shown to exert cytotoxicity via inducing apoptosis in cancer cell line.

•Three cytochalasans along with two new ent-eudesmane sesquiterpenes and one known ent-eudesmane sesquiterpene were isolated.•Phenochalasin B (4) could induce the PARP cleavage in a time- and dose-dependent manner and induce apoptosis in HepG 2 liver cancer cells.•[12]-Cytochalasin (5) could strongly inhibite the expression of CDK 4 with a time dependent manner which may lead to the apoptosis in HepG 2 cell line.•[1,3] Dioxacyclotridecino (6) which possess the same skeleton did not show any cytotoxic activity.Available online from an cytotoxic endophytic fungus Botryotinia fuckeliana A-S-3, three cytochalasans phenochalasin B (4), [12]-cytochalasin (5) and one [1,3] dioxacyclotridecino (6), along with two new ent-eudesmane sesquiterpenes, 1-keto-4α,15-epoxyeudesm-11-ol (1), and ent-4(15)-eudesmen-5,6-ol-1-one (2), and one known ent-eudesmane sesquiterpene ent-4(15)-eudesmen-11-ol-1-one (3) were isolated. The structures of these compounds were elucidated by interpretation of spectroscopic data. Among these compounds, two cytotoxic constituents were identified.Download full-size image