Oenin

All chemicals, cell culture media and supplements used for the study were purchased from Sigma-Aldrich (Budapest, Hungary). Fluorescent dyes including calcein-acetoxymethylester (calcein-AM) and Alexa 647 succinimidyl ester (A647) were obtained from Life Technologies, Inc. (Carlsbad, CA, USA). UIC2, the Pgp-specific mAb, was purified from hybridoma supernatants by affinity chromatography. The antibody-producing hybridoma cell line was obtained from the American Type Culture Collections (Manassas, VA, USA). UIC2 mAb was labeled with A647, and it was purified from the unconjugated dye by gel filtration using a Sephadex G-50 column. The dye-to-protein labeling ratio was determined for every antibody preparation and was found to be around 3. Lipophilic transporter substrates/inhibitors (e.g., calcein-AM and cyclosporine A (CsA)) were dissolved in dimethyl-sulfoxide (DMSO). All tested polyphenols (quercetin, quercetin-3-glucoside, naringenin, ellagic acid, cynidin-3-O-sophroside, oenin, malvin, kuromanin, keracyanin, caffeic acid, chlorogenic acid, trans-ferulic acid, catechin, epicatechin and narcissoside) were HPLC grade (with 99% purity) and were purchased from Sigma-Aldrich (Budapest, Hungary). Polyphenols were dissolved in DMSO or water according to the manufacturer’s instructions. For all experiments, the final DMSO concentration of samples was less than 1% (v/v).

The following compounds, with purity between 90–98% according to the manufacturer, were obtained from Sigma (St. Louis, MO): hydroxytyrosol, baicalein, cis‐2‐decenoic acid, morin, oenin, vitamin D3 (1,25‐dihydroxycholecalciferol) and vitamin C (ascorbic acid). The following compounds, with purity between 97–99% according to the manufacturer, were purchased from Tocris Bioscience (Bristol, UK): rosmarinic acid, kaempferol, piceatannol, rottlerin, luteolin and fisetin. Other reagents used in this study were organic kelp with standardized iodine content (i.e. 150 μg ml⁻¹ as 100% Daily Value) purchased from World Organic Ltd. (Auckland, New Zealand), and monolaurin (Lauricidin^®) purchased from Med‐Chem Laboratories, Inc., (Goodyear, AZ) as a pure sn‐1 monolaurin (glycerol monolaurate) derived from coconut oil.