Seven drimane-type sesquiterpenoids from an earwig-associated Aspergillus sp.

Drimane-type sesquiterpenoids are widely distributed in fungi. From the ethyl acetate extract of the earwig-derived Aspergillus sp. NF2396, seven new drimane-type sesquiterpenoids, named drimanenoids A−G ( 1 − 7 ), were isolated. Their structures were elucidated by diverse spectroscopic analysis including high-resolution ESI-MS, one- and two-dimensional NMR spectroscopy. Drimanenoids A−F ( 1 − 6 ) are new members of drimane-type sesquiterpenoid esterified with unsaturated fatty acid side chain at C-6. Drimanenoids C ( 3 ), D ( 4 ) and F ( 6 ) showed antibacterial activity against five types of bacteria with different inhibition diameters. Drimanenoid D ( 4 ) exhibited moderate cytotoxicity against human myelogenous leukemia cell line K562 with an IC₅₀ value of 12.88 ± 0.11 μmol·L⁻¹.