TY - JOUR T1 - Polymethoxylated Flavones in Orange Juice Are Inhibitors of P-glycoprotein but Not Cytochrome P450 3A4 JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 230 LP - 236 VL - 293 IS - 1 AU - Hitomi Takanaga AU - Ayako Ohnishi AU - Shiho Yamada AU - Hirotami Matsuo AU - Satoshi Morimoto AU - Yukihiro Shoyama AU - Hisakazu Ohtani AU - Yasufumi Sawada Y1 - 2000/04/01 UR - http://jpet.aspetjournals.org/content/293/1/230.abstract N2 - 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 [3H]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 [3H]vinblastine but significantly increased the steady-state uptake, as did cyclosporin A (20 μM), an inhibitor of P-gp. No significant effect on the uptake of 3-O-[3H]methylglucose or [14C]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 [3H]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 [3H]vinblastine by Caco-2 cells in a concentration-dependent manner. The order of potency of these compounds at the concentration of 50 μM was tangeretin > HMF > nobiletin. None of these methoxyflavones inhibited 6β-hydroxylation of testosterone catalyzed by CYP3A4. The ethyl acetate extract of orange juice and these methoxyflavones also increased steady-state [3H]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. The American Society for Pharmacology and Experimental Therapeutics ER -