Cytotoxic seco-cytochalasins from an endophytic Aspergillus sp. harbored in Pinellia ternata tubers.

Six new seco-cytochalasins A-F (1-6), two new asperlactones G-H (7-8) along with three known cytochalasins (9-11) were isolated from the solid cultures of an endophytic fungus Aspergillus sp. Their structures were elucidated by comprehensive spectral analysis, and their absolute configurations were determined through Mo2(OCOCH3)4-induced electronic circular dichroism (ECD) spectra and Rh2(OCOCF3)4-induced ECD experiment. Compounds 5 and 6 were rare seco-cytochalasins possessing an α, β-unsaturated furanone structure in their side-chains. These isolates exhibited cytotoxicity against human lung cancer A-549 cell line with IC50 values ranging from 7.8 to 70.2 μM. At the concentration of 16 μM, compound 4 also exerted a 3-fold enhancement of doxorubicin susceptibility on doxorubicin-resistant human breast cancer (MCF-7/DOX) cell line.