Ochracenes A-I, Humulane-Derived Sesquiterpenoids from the Antarctic Fungus Aspergillus ochraceopetaliformis.

Nine new humulane-derived sesquiterpenoids, ochracenes A-I (1-9), were isolated from the Antarctic fungus Aspergillus ochraceopetaliformis SCSIO 05702. Their structures including absolute configurations were elucidated on the basis of spectroscopic analysis, Mosher's method, and electronic circular dichroism analysis. Compared with previous humulane-type sesquiterpenoids, ochracenes A-I (1-9) featured novel carbon skeletons with corresponding methyl migration, ring cleavage, and carbon loss. Two unprecedented 8,9-secocyclic sesquiterpenoids (2 and 3) exhibited inhibitory effects on lipopolysaccharide-induced NO release in RAW 264.7 mouse macrophage cell lines with IC50 values of 14.6 ± 0.5 and 18.3 ± 1.7 μM, respectively.