Monalbidins A-E, Decalins with Potential Cytotoxic Activities from Marine Derived Fungus Monascus albidus BB3

Five new decalins, monalbidins A-E (1, 2 and 7-9), together with 16 known compounds (3-6 and 10-21), were isolated from the AcOEt extract of marine derived fungus Monascus albidus BB3 cultured in GPY medium. Among the known compounds, 1-hydroxymonacolin L (11), dehydromonacolin J (15), 8-O-acetylmonacolin J (19) and O-acetylmonacolin K (21) were separated from natural sources for the first time. Their structures were determined by comprehensive analysis on the 1D and 2D NMR, HR-ESI-MS, UV and IR data, and their absolute configurations were assigned by experimental and calculated ECD data, and X-ray single-crystal diffraction analysis. Monalbidins C and D (7 and 8), monacolin K methyl ester (13), dehydromonacolin L (14), dehydromonacolin K (16), monacolin K (20) and O-acetylmonacolin K (21) showed moderate cytotoxicity against human cancer cell lines SUNE1, HepG2, QGY7701, HCT116 and MDA-MB-231.