title: Effects of the flavonoids biochanin A, morin, phloretin, and silymarin on P-glycoprotein-mediated transport.
abstract: Flavonoids are constituents of fruits, vegetables, and plant-derived beverages, as well as components in herbal-containing dietary supplements. The objective of this investigation was to characterize the effect of flavonoids on P-glycoprotein (P-gp)-mediated cellular efflux and to determine the molecular mechanism(s) of the flavonoid-drug interaction. Studies were conducted in the sensitive and multidrug resistant human breast cancer cell lines MCF-7 and MDA435/LCC6 and examined the effects of the flavonoids biochanin A, morin, phloretin, and silymarin on daunomycin (DNM) accumulation and doxorubicin cytotoxicity. The potential mechanism(s) involved in the interaction was evaluated by determining flavonoid effects on 1) P-gp ATPase activity, 2) [(3)H]azidopine photoaffinity labeling of P-gp, and 3) cellular P-gp levels. The flavonoids increased [(3)H]DNM accumulation in P-gp positive cells, but not P-gp negative cells, and these effects were both flavonoid concentration- and P-gp expression level-dependent. Biochanin A and silymarin potentiated doxorubicin cytotoxicity in P-gp positive cells. Biochanin A and phloretin stimulated, whereas morin and silymarin inhibited P-gp ATPase activity, confirming that these flavonoids interact with P-gp. Morin and silymarin significantly inhibited [(3)H]azidopine photoaffinity labeling of P-gp, suggesting a direct interaction with P-gp substrate binding. A 24-h preincubation with all flavonoids, followed by flavonoid removal, did not alter cellular P-gp level in P-gp positive cells. In conclusion, biochanin A, morin, phloretin, and silymarin all inhibited P-gp-mediated cellular efflux and the mechanism of the interaction involved, at least in part, a direct interaction. The findings of this study indicate a potential for significant flavonoid-drug interactions with P-gp substrates.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, State University of New York, Amherst, New York, USA.
authors.forename: Shuzhong
authors.initials: S
authors.lastname: Zhang
authors.forename: Marilyn E
authors.initials: ME
authors.lastname: Morris
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000903:Antibiotics, Antineoplastic / Q000493:pharmacokinetics; D001386:Azides / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D003630:Daunorubicin / Q000493:pharmacokinetics; D004095:Dihydropyridines / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology; D004347:Drug Interactions; D005419:Flavonoids / Q000494:pharmacology*; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D010693:Phloretin / Q000494:pharmacology; D019920:Photoaffinity Labels; D012838:Silymarin / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D014316:Tritium; D014407:Tumor Cells, Cultured; D047309:Flavones
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000251:Adenosine Triphosphatases; D000903:Antibiotics, Antineoplastic; D001386:Azides; D003630:Daunorubicin; D004095:Dihydropyridines; D004317:Doxorubicin; D005419:Flavonoids; D019833:Genistein; D010693:Phloretin; D019920:Photoaffinity Labels; D012838:Silymarin; D014316:Tritium; C041130:azidopine; C008548:morin; D047309:Flavones; C004541:biochanin A