Myricetin (MYR) and ampelopsin (AMP, or dihydromyricetin) are flavonoid aglycones found in certain plants and dietary supplements. During the presystemic biotransformation of flavonoids, mainly sulfate and glucuronide derivatives are produced, which are the dominant metabolites in the circulation. In this study, we tested the interactions of MYR, myricetin-3'-O-sulfate (M3'S), AMP, and ampelopsin-4'-O-sulfate (A4'S) with human serum albumin (HSA), cytochrome P450 enzymes (CYPs), and organic anion-transporting polypeptides (OATPs) using in vitro models, including the recently developed method for measuring flavonoid levels in living cells. M3'S and MYR bound to albumin with high affinity, and they showed moderate displacing effects versus the Site I marker warfarin. MYR, M3'S, AMP, and A4'S exerted no or only minor inhibitory effects on CYP2C9, CYP2C19, and CYP3A4 enzymes. M3'S and MYR caused considerable inhibitory actions on OATP1B1 at low micromolar concentrations (IC50 = 1.7 and 6.4 μM, respectively), while even their nanomolar levels resulted in strong inhibitory effects on OATP2B1 (IC50 = 0.3 and 0.4 μM, respectively). In addition, M3'S proved to be a substrate of OATP1B1 and OATP2B1. These results suggest that MYR-containing dietary supplements may affect the OATP-mediated transport of certain drugs, and OATPs are involved in the tissue uptake of M3'S.

Department of Laboratory Medicine Medical School University of Pécs Pécs Hungary

Department of Pharmacology Faculty of Pharmacy University of Pécs Pécs Hungary

Doctoral School of Biology Institute of Biology Eötvös Loránd University Budapest Hungary

Drug Resistance Research Group Institute of Molecular Life Sciences Research Centre for Natural Sciences HUN REN Budapest Hungary

Institute of Microbiology of the Czech Academy of Sciences Prague Czech Republic

Molecular Medicine Research Group János Szentágothai Research Centre University of Pécs Pécs Hungary

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