Prenylated xanthones as potential P-glycoprotein modulators.

Dimethylallyl (DMA) derivatives of a naturally occurring xanthone (decussatin 1) were prepared. Their activity as potential P-glycoprotein inhibitors was monitored by affinity of direct binding and compared to that of corresponding DMA-flavones. Both classes of compounds exhibited the same structure-activity relationships. Decreasing polarity enhanced the binding affinity for the P-glycoprotein C-terminal cytosolic domain since DMA derivatives were more active, but unsubstituted hydroxyl group close to the carbonyl was required for efficient activity.