Isolation and identification of diverse steroids as Escherichia coli β-glucuronidase inhibitors from the Submerge-cultured mycelia of Hirsutella sinensis.

The ethanol extract of the submerge-cultured mycelia of Hirsutella sinensis (SCMHS) inhibited the Escherichia coli β-glucuronidase (EcGUS) in vitro. In-depth chemical investigation furnished 26 steroids, including a new compound hirsusterol A (1) featuring a rare 14,15-seco steroidal moiety and 25 known compounds with varied chemical diversity. The plausible biosynthetic pathway for hirsusterol A (1) was proposed. Except for ergosterol (22) and ergosterol peroxide (23), all the other compounds have never been obtained from H. sinensis previously. Compounds 8 and 23 were found to be potent uncompetitive inhibitors of EcGUS. This is the first report of these two steroids as EcGUS inhibitors. The findings of this study preliminary clarified the active ingredient underlying the EcGUS inhibition activity of SMCHS and provided potential drug leads for the development of new EcGUS inhibitors.