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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