Rare prenyleudesmane diterpenoids with reversal of multidrug resistance activity from Dysoxylum densiflorum.

Dysoxydenins A-M (1-13), thirteen new and rare prenyleudesmane diterpenoids were isolated and elucidated from the fruits of Dysoxylum densiflorum. Their structures, especially the absolute configurations of bridged C-5/C-7 in double ring skeleton and C-11 or C-14 in the flexible side chain, were elucidated through a comprehensive approach involving nuclear magnetic resonance (NMR) spectroscopy, electronic circular dichroism (ECD), Mosher, quantum chemical calculations, and single-crystal X-ray crystallography with Cu Kα radiation. Compounds 1, 3-7, 9, 10 shown significant reversing effects on multidrug resistance in MCF-7/doxorubicin (DOX) cells, which of 3 was higher than that of positive drug Verapamil. These rare but abundant prenyleudesmane diterpenoids also have the potential to serve as the chemotaxonomic marker of Dysoxylum plant differing from other Meliaceae plant.