Roemerine, an aporphine alkaloid, isolated from the leaves of Annona senegalensis, functions by interacting with P-glycoprotein. Roemerine reverses the multidrug-resistance phenotype with cultured cells[1].
[1]. M You, et al. (-)-Roemerine, an Aporphine Alkaloid From Annona Senegalensis That Reverses the Multidrug-Resistance Phenotype With Cultured Cells. J Nat Prod. 1995 Apr;58(4):598-604.