Nitrobenzoyl Sesquiterpenoids with Cytotoxic Activities from a Marine-Derived Aspergillus ochraceus Fungus

Nitrobenzoyl sesquiterpenoids are rare from natural sources. Two new nitrobenzoyl sesquiterpenoids, insulicolide B (1) and insulicolide C (3), and the new natural product 14-O-acetylinsulicolide A (2) were isolated from culture extracts of the marine-derived fungus Aspergillus ochraceus Jcma1F17, together with three known nitrobenzoyl sesquiterpenoids (4-6) and a derivative sesquiterpenoid (7). The structures of the new compounds, including their absolute configurations, were determined by NMR and MS spectroscopic data analyses and comparison between the calculated and experimental ECD spectra. The nitrobenzoyl sesquiterpenoids (1-6) were evaluated for their cytotoxicities against three renal carcinoma cell lines, ACHN, OS-RC-2, and 786-O cells, and compounds 2, 4, and 5 displayed activities with IC₅₀ values of 0.89 to 8.2 μM. Further studies indicated that 2 arrested the cell cycle at the G0/G1 phase at a concentration of 1 μM and induced late Apoptosis at a concentration of 2 μM after a 72 h treatment of 786-O cells.