Polymethoxylated flavones in orange juice are inhibitors of P-glycoprotein but not cytochrome P450 3A4.
The presence in orange juice of compounds that specifically inhibit the P-glycoprotein (P-gp) drug efflux transporter, but not the cytochrome P450 (CYP) isozyme CYP3A4, was investigated. The uptake of [(3)H]vinblastine, a substrate of P-gp, by Caco-2 cells was measured. An ethyl acetate extract of orange juice did not affect the initial uptake rate of [(3)H]vinblastine but significantly increased the steady-state uptake, as did cyclosporin A (20 microM), an inhibitor of P-gp. No significant effect on the uptake of 3-O-[(3)H]methylglucose or [(14)C]phenylalanine by Caco-2 cells was found, compared with the control. When the extract was separated on a Cosmosil column, the eluate with 70% methanol showed the most potent ability to increase [(3)H]vinblastine uptake. Additional separation of the 70% methanol eluate on a silica gel column with hexane-acetone (3:1) gave 3,3',4',5,6,7,8-heptamethoxyflavone (HMF) and 4',5,6,7,8-pentamethoxyflavone (tangeretin). HMF, tangeretin, and 3',4',5,6,7,8-hexamethoxyflavone (nobiletin), another methoxyflavone contained in orange juice, all increased the steady-state uptake of [(3)H]vinblastine by Caco-2 cells in a concentration-dependent manner. The order of potency of these compounds at the concentration of 50 microM was tangeretin > HMF > nobiletin. None of these methoxyflavones inhibited 6beta-hydroxylation of testosterone catalyzed by CYP3A4. The ethyl acetate extract of orange juice and these methoxyflavones also increased steady-state [(3)H]vinblastine uptake by LLC-GA5-COL300 cells (a cell line transfected with human MDR1 cDNA). We conclude that these methoxyflavones enhanced vinblastine uptake by specifically inhibiting drug efflux via P-gp. They may have potential as agents for reversing multidrug resistance or for recovering the bioavailability of certain drugs.
Takanaga
H
H
Department of Pharmaceutics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Ohnishi
A
A
Yamada
S
S
Matsuo
H
H
Morimoto
S
S
Shoyama
Y
Y
Ohtani
H
H
Sawada
Y
Y
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors*; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000378:metabolism; D001628:Beverages / Q000032:analysis*; D018938:Caco-2 Cells; D002470:Cell Survival / Q000187:drug effects; D002957:Citrus / Q000737:chemistry*; D016572:Cyclosporine / Q000494:pharmacology; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D047309:Flavones; D005419:Flavonoids / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D006900:Hydroxylation; D018374:LLC-PK1 Cells; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors*; D012997:Solvents; D013552:Swine; D013739:Testosterone / Q000378:metabolism; D014747:Vinblastine / Q000378:metabolism
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000972:Antineoplastic Agents, Phytogenic; D065607:Cytochrome P-450 Enzyme Inhibitors; D047309:Flavones; D005419:Flavonoids; D012997:Solvents; D013739:Testosterone; D014747:Vinblastine; D016572:Cyclosporine; C008661:nobiletin; D006899:Mixed Function Oxygenases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; C059006:tangeretin