Four new steroids from the endophytic fungus Chaetomium sp. M453 derived of Chinese herbal medicine Huperzia serrata

•The chemical constituents of the entophytic fungus Chaetomium sp. M453 were investigated.•Three unusual C25 steroids, neocyclocitrinols E-G and 3β-hydroxy-5,9-epoxy-(22E,24R)-ergosta-7,22-dien-6-one were isolated.•Their structures were elucidated by extensive 1D- and 2D-NMR, and HR-ESI-MS experiments.•The absolute configuration of 1 was determined by X-ray crystallographic analysis and CD analyses.•Compound 4 showed weak acetylcholinesterase inhibitory activity.

An endophytic fungus, Chaetomium sp. M453, was isolated from Huperzia serrata (Thunb. ex Murray) Trev. and subjected to phytochemical investigation. Three unusual C25 steroids, neocyclocitrinols E-G (1-3), and 3β-hydroxy-5,9-epoxy-(22E,24R)-ergosta-7,22-dien-6-one (4) together with three known steroids were isolated from solid fermentation products of the fungus, which were elucidated by extensive spectroscopic analyses, including 1D-, 2D-NMR, and HR-ESI-MS experiments. The absolute configuration of 1 was determined by X-ray crystallographic analysis and CD analyses. The acetylcholinesterase inhibitory activities of compounds 1-4 were tested in vitro. Compound 4 showed weak acetylcholinesterase inhibitory activity.

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