C25 steroids from the marine mussel-derived fungus Penicillium ubiquetum MMS330

Abstract Two new unusual C25 steroid epimers, 24-O-methyl-24-epi-cyclocitrinol (1) and 24-O-methylcyclocitrinol (2), together with the known oxylipin α-dimorphecolic acid (3), were isolated from the extract of cultures of a Penicillium ubiquetum MMS330 strain sampled from the blue mussel Mytilus edulis. The structures of the new compounds were established based on 1D and 2D NMR spectral analyses and CP3 conformation analysis. LC–MS dereplication of other C25 steroids in culture extracts was also performed on the basis of their HRMS/MS fragmentation patterns, allowing to detect other analogues. Biological activities of compounds 1 and 2 were evaluated as a mixture on the two human cancer cell lines KB and MCF-7.