Rare C25 Steroids Produced by Penicillium chrysogenum P1X, a Fungal Endophyte of Huperzia serrata

Three new metabolites, norcyclocitrinol A (1), erythro-11-hydroxyneocyclocitrinol (2), and pesudocyclocitrinol A (3), along with six known analogs, i.e., neocyclocitrinols A-D (4-7, resp.), cyclocitrinol (8), and 24-epicyclocitrinol (9), were isolated and identified from the culture broth of Penicillium chrysogenum P1X, a fungal endophyte of Huperzia serrata. Compounds 1-9 were identified by spectroscopic methods to share the same C-25-steroid skeleton featuring an unusual bicyclo[4.4.1] A/B ring system. In particular, 1 represents the first example of a C-25 steroid with a bisnor C-atom side chain. All compounds were evaluated for their cytotoxic activities against HeLa and HepG2 cell lines. However, none of them exhibited a significant cytotoxicity at a concentration of 20 mu M.