Seven new cytotoxic phenylspirodrimane derivatives from the endophytic fungus Stachybotrys chartarum

Abstract

Seven undescribed phenylspirodrimane derivatives, stachybochartins A–G (1–7), and four known analogues (8–11) were isolated from the endophytic fungus Stachybotrys chartarum obtained from Pinellia ternata. Stachybochartins A–D are four rare C–C-coupled dimeric derivatives and stachybochartin G features a seco-bisabosqual skeleton. Their structures and configurations were elucidated via spectroscopic analysis, electronic circular dichroism (ECD) calculations, the ECD exciton chirality method and the modified Mosher's method. Stachybochartins A–D and G displayed cytotoxic activities against MDA-MB-231 breast cancer cells and U-2OS osteosarcoma cells, with IC₅₀ values ranging from 4.5 to 21.7 μM. Stachybochartins C and G exerted strong anti-proliferative activities against U-2OS cells in concentration- and time-dependent manners and induced apoptosis.