Abstract
The flavonoids quercetin and kaempferol are major constituents of Ginkgo biloba extract. The ATP-binding cassette efflux transporter, breast cancer resistance protein (Bcrp, Abcg2), is involved in the transport of quercetin and represents a possible mechanism for the low bioavailability of quercetin. Our objective was to investigate whether kaempferol inhibits Bcrp-mediated quercetin efflux and determine whether it is a substrate for BCRP. The intracellular uptake of kaempferol, with and without specific inhibitors, was determined in Bcrp-expressing cells. The transport of quercetin or kaempferol (10 μM) across Madin-Darby canine kidney (MDCK) cell monolayers was investigated in both the apical (A)-to-basolateral (B) and B-to-A directions. Samples were analyzed using liquid chromatography-tandem mass spectrometry. Compared with the quercetin alone group, the transport ratio decreased 11.6-fold (from 97.5 to 8.37) in the presence of kaempferol in MDCK/Bcrp1 cells, indicating that kaempferol is a Bcrp inhibitor. The intracellular concentration of kaempferol was significantly increased in the presence of N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918), a potent Bcrp inhibitor, suggesting that kaempferol may also be a Bcrp substrate. Moreover, in MDCK/Bcrp1 cells, the Papp, B-A of kaempferol was much higher (17.7 ± 3.8 × 10−6 cm/s) than the Papp, A-B (0.279 ± 0.037 × 10−6 cm/s), with a transport ratio of 63.4. In contrast, the transport ratio of kaempferol was only 0.68 in Bcrp1-negative MDCK/Mock cells. We report for the first time that kaempferol is a Bcrp substrate, and our results indicate that kaempferol inhibits Bcrp-mediated quercetin efflux. Intestinal efflux by Bcrp may represent one possible mechanism for the low bioavailability of kaempferol. The use of flavonoids in combination may increase their bioavailability through transport interactions.
Footnotes
This work was supported in part by the Susan G. Komen Breast Cancer Foundation [Grant BCTR0601385].
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
doi:10.1124/dmd.110.035212.
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ABBREVIATIONS:
- BCRP/Bcrp
- Abcg2, breast cancer resistance protein
- P-gp
- P-glycoprotein
- MRP2
- multidrug resistance protein 2
- B
- basolateral
- A
- apical
- MDCK
- Madin-Darby canine kidney
- PBS
- phosphate-buffered saline
- HBSS
- Hanks' balanced salt solution
- GF120918
- N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide
- LC
- liquid chromatography
- MS/MS
- tandem mass spectrometry
- MS
- mass spectrometry
- EGCG
- epigallocatechin-3-gallate
- DGT
- decaffeinated green tea.
- Received June 30, 2010.
- Accepted December 7, 2010.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
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