(-)-(S)-Equol (4',7-Dihydroxyisoflavan) is an orally bioavailable, non-steroidal estrogen naturally produced by the metabolism of the isoflavonoid daidzein by human intestinal microflora, with potential chemoprotective and estrogen receptor (ER) modulating activities. S-equol preferentially binds to and activates the beta isoform of ER in certain target tissues, while having an antagonistic effect in other tissues. This modulates the expression of ER-responsive genes in a tissue-specific manner. This agent may increase bone mineral density, affect vasomotor symptoms, and may decrease the proliferation rate of susceptible cancer cells. In addition, this agent interferes with the activity of enzymes involved in steroid biosynthesis. S-equol inhibits dihydrotestosterone (DHT) production and may inhibit the proliferation of androgen-driven prostate cancer. S-equol is the biologically active enantiomer while R-equol is essentially inactive and has a weak affinity for alpha-ER.

ERRβ:0.73 nM(Ki)

Equol是由肠道微生物作用于大豆植物雌激素daidzein产生的代谢产物。该化合物对两种ER（雌激素接受器，包括ERalpha和ERbeta）具有更高的亲和力。Equol以R-equol和S-equol的对映异构体存在，其中S-equol对ERbeta具有较高的结合亲和力，Ki值为16 nM；而R-equol的结合力相对较弱，偏好与ERalpha结合，Ki值为50 nM。[1] 在抗氧化活性方面，Equol优于所有其他异黄酮。[2] Equol具有抗雌激素特性。[3] 在刺激雌激素反应方面，Equol的效力是daidzein的100倍。与daidzein相比，Equol在与3 H-雌二醇竞争结合到ER时更为有效。Equol以浓度依赖的方式促进MCF-7细胞的生长。尽管Equol表现出雌激素活性，但将MCF-7细胞同时暴露于Equol和雌二醇中，可以有效降低pS2 mRNA表达，从而导致ER mRNA表达的下调。[4]

Each well of a 24-well plate is seeded with 1 × 105 MCF-7 cells in 1 mL of media B. Twenty-four hours after plating, equol at the indicated concentration is added. Equol is dissolved in ethanol (final concentration of ethanol in the medium is 1%). The medium is changed every 24 hours and equol is replenished with each change. Cell growth is determined on the sixth day by the sulphorhodamine colorimetric assay. After colour development, aliquots are pipetted into a 96-well microtitre plate and the absorbance is determined at 570 nm using an Elisa microplate reader.(Only for Reference)