Niduenes A−F, six functionalized sesterterpenoids with a pentacyclic 5/5/5/5/6 skeleton from endophytic fungus Aspergillus nidulans

Niduenes A−F (1−6), six novel sesterterpenoids with unprecedented 5/5/5/5/6 pentacyclic ring skeleton were isolated from endophytic fungus Aspergillus nidulans. Compounds 1 and 2 represent the first examples of aromatic pentacyclic sesterterpenoids. Their structures and configurations were elucidated by spectroscopic data and single-crystal X-ray diffraction analyses. Compound 4 demonstrated potent resensitization of SW620/AD300 cells to paclitaxel (PTX). Rhodamine 123 accumulation assay and docking analysis further support that 4 inhibitory the efflux function of P-glycoprotein (P-gp).