The Flavonoid Kaempferol Is Responsible for the Majority of Estrogenic Activity in Red Wine

Abstract

The preventive effect of moderate red wine consumption on cardiovascular and hormone-related diseases and the estrogenic activity of red wines have been attributed to resveratrol. In the present study, we wished to determine which polyphenols in red wine have a high affinity for estrogen receptors (ER). The estrogenicity of the red wines, assessed with ligand binding and yeast transactivation assays, was primarily mediated by estrogen receptor β (ERβ), with equivalent concentrations ranging from 40 to 140 nmol/L. Estrogenicity was more weakly mediated by estrogen receptor α (ERα), with equivalent concentrations of ~14 nmol/L and minimal ERα transactivation. Kaempferol and apigenin strongly bound to ERβ, with inhibitory concentrations (IC₅₀) of 5.1 × 10⁻⁸ M and 3.8 × 10⁻⁷ M, respectively. <i>trans</i>-Resveratrol and quercetin were moderate binders, with IC₅₀ of 4.0 × 10⁻⁶ M and 1.1 × 10⁻⁶ M, respectively; naringenin and myricetin bound with low affinity ERβ (1.0 × 10⁻⁵ M). Most compounds had low affinity to ERα, with IC₅₀ greater than 1 × 10⁻⁵ M; the exceptions were kaempferol and apigenin, with IC₅₀ of 8.2 × 10⁻⁶ M and 2.3 × 10⁻⁶ M, respectively. In this study of eight wines, only 2% of the estrogenic activity was due to <i>trans</i>-resveratrol, thus suggesting revision of the hypothesis that the estrogenicity of red wines is due to <i>trans</i>-resveratrol. In light of the possible positive health effects of ER-β ligands in red wine, vintners may aim to optimize the polyphenol composition in wines without changing sensory properties.