Scabrosteroids A-D, Four Pyrrolidinone-Ergosterol Heterodimers from Penicillium scabrosum FXI744.

Scabrosteroids A-D (1-4), four novel steroidal heterodimers, were isolated from Penicillium scabrosum FXI744. These compounds represent the first naturally occurring pyrrolidinone-ergosterol hybrids, linked by a C-3/C-3' bond between pyrrolidinone and ergosterol moieties. Their structural elucidation, including the determination of absolute configurations, was accomplished using HRESIMS, NMR, X-ray crystallography, and ECD calculation. A plausible biosynthetic pathway for these metabolites was proposed. Biological evaluation revealed that compounds 1-4 inhibited NO production with IC50 values ranging from 9.5 to 14.4 μM, and compounds 1 and 4 also showed moderate in vitro immunosuppressive effects.