7β,8β-epoxy-(22E,24R)-24-methylcholesta-4,22-diene-3,6-dione (1), a new steroid, along with five known analogues (2-6), was isolated from the deep sea-derived fungus, Aspergillus penicillioides SD-311. Strikingly, 1 possessed a rare 7,8-epoxidation moiety. Meanwhile, this is the first time to report natural products from this fungus species. The structures were established by extensive spectroscopic analysis. The absolute configuration was determined by X-ray diffraction experiments. Compound 1 showed antibacterial activity against Vibrio anguillarum with MIC value of 32.0 µg/mL, while 2 displayed inhibitions against Edwardsiella tarda and Micrococcus luteus with MIC values both of 16 µg/mL.
Keywords: 7β,8β-epoxy steroid; Aspergillus penicillioides; deep sea-derived fungus; marine natural products.