Tricholosterols A–D, four new ergosterol derivatives from the mushroom Tricholoma terreum

Four undescribed steroids have been identified from fruiting bodies of the mushroom Tricholoma terreum. [Display omitted] •Four undescribed steroids have been obtained from Tricholoma terreum.•One compound possesses a rare D ring-opening skeleton.•Two compounds exhibited NO production inhibitory activities.•This is the first report of steroids from T. terreum. Four ergosterol derivatives, named tricholosterols A–D (1–4), have been isolated from the fruiting bodies of Tricholoma terreum. Their chemical structures have been determined using a combination of spectroscopic analysis as well as computational methods. Compound 1 possesses a rare D-ring opening ergosterol skeleton, while compounds 2–4 are rare degraded ergosterols. Compounds 1 and 4 exhibited moderate inhibitory activity against NO production with IC50 values of 27.6 and 31.8 μM, respectively. This is the first report of steroids from T. terreum.