Cytotoxic Ergosteroids from a Strain of the Fungus Talaromyces adpressus

Nine new ergosteroids (1–9) and seven known ones (10–16) were isolated from Talaromyces adpressus. Their structures and absolute configurations were determined by the interpretation of NMR spectroscopic data, HRESIMS, ECD calculations, and single-crystal X-ray diffraction analyses. Structurally, compound 1 was an ergosteroid with two epoxy and a 3α-OH group at ring A, while compounds 8 and 9 had a contracted ring A with a peroxy bridge between C-3 and C-9, which were reported for the first time. Compounds 2–6, 9, 11, and 15 displayed cytotoxic activities with IC50 values ranging from 0.4 to 32 μM, and compound 7 exhibited an immunosuppressive effect against LPS-induced B lymphocyte proliferation with an IC50 value of 8.6 μM. The structure–activity relationships of these compounds are briefly discussed.