An isoquinoline alkaloid from the Chinese herbal plant Corydalis yanhusuo W.T. Wang inhibits P-glycoprotein and multidrug resistance-associate protein 1

► An alkaloid from herbal plant inhibits P-gp and MRP1 as a competitive inhibitor. ► The alkaloid glaucine suppressed expression of both genes. ► Glaucine can reverse multidrug resistance of cancer cells effectively.