Tricholosterols A-D, four new ergosterol derivatives from the mushroom Tricholoma 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.