Editing Equol (section)

==Pharmacology==

===Estrogen receptor binding===
(''S'')-equol is a [[nonsteroidal]], selective [[agonist]] of [[ERβ]] (K<sub>i</sub> = 16 nM) with 13-fold selectivity for ERβ over [[ERα]].<ref name="MuthyalaJu2004" /> Relative to (''S'')-equol, (''R'')-equol is less potent and binds to ERα (K<sub>i</sub> = 50 nM) with 3.5-fold selectivity over ERβ.<ref name="MuthyalaJu2004" /> (''S'')-Equol has about 2% of [[estradiol]]'s binding affinity for human [[estrogen receptor alpha]] (ERα) and 20% of estradiol's binding affinity for human [[estrogen receptor beta]] (ERβ). The preferential binding of (''S'')-equol to ERβ vs. ERα and in comparison to that of estradiol suggests the molecule may share some of the characteristics of a [[selective estrogen receptor modulator]] (SERM).<ref>{{cite journal|last=Setchell|first=KD |author2=Clerici, C |author3=Lephart, ED |author4=Cole, SJ |author5=Heenan, C |author6=Castellani, D |author7=Wolfe, BE |author8=Nechemias-Zimmer, L |author9=Brown, NM |author10=Lund, TD |author11=Handa, RJ |author12=Heubi, JE|title=S-equol, a potent ligand for estrogen receptor beta, is the exclusive enantiomeric form of the soy isoflavone metabolite produced by human intestinal bacterial flora |journal=[[The American Journal of Clinical Nutrition]]|date=May 2005|volume=81|issue=5|pages=1072–9|pmid=15883431|doi=10.1093/ajcn/81.5.1072 |doi-access=free }}</ref> Equol has been found to act as an [[agonist]] of the [[GPER]] (GPR30).<ref name="ProssnitzBarton2014">{{cite journal|last1=Prossnitz|first1=Eric R.|last2=Barton|first2=Matthias|title=Estrogen biology: New insights into GPER function and clinical opportunities|journal=Molecular and Cellular Endocrinology|volume=389|issue=1–2|year=2014|pages=71–83|issn=0303-7207|doi=10.1016/j.mce.2014.02.002|pmid=24530924|pmc=4040308}}</ref>

===Pharmacokinetics===
(''S'')-Equol is a very stable molecule that essentially remains unchanged when digested, and this lack of further metabolism explains its very quick [[Absorption (pharmacology)|absorption]] and high [[bioavailability]].<ref>{{cite journal|last=Setchell|first=KD|author2=Zhao, X |author3=Jha, P |author4=Heubi, JE |author5=Brown, NM |title=The pharmacokinetic behavior of the soy isoflavone metabolite S-(-)equol and its diastereoisomer R-(+)equol in healthy adults determined by using stable-isotope-labeled tracers |journal=[[The American Journal of Clinical Nutrition]]|date=Oct 2009|volume=90|issue=4|pages=1029–37|pmid=19710188|doi=10.3945/ajcn.2009.27981|pmc=2744624}}</ref>
When (''S'')-equol is consumed, it is rapidly absorbed and achieves a T<sub>max</sub> (rate of [[peak plasma concentration]]) in two to three hours. In comparison, the T<sub>max</sub> of daidzein is 4 to 10 hours because daidzein exists in [[glycoside]] (with a glucose side chain) form. The body must convert daidzein to its [[aglycone]] form (without the glucose side chain) via removal of the sugar side chain during digestion before it can use daidzein.  If consumed directly in aglycone form, daidzein has a T<sub>max</sub> of one to three hours.<ref>{{cite journal|last=Setchell|first=KD|author2=Zhao, X |author3=Shoaf, SE |author4=Ragland, K |title=The pharmacokinetics of S-(-)equol administered as SE5-OH tablets to healthy postmenopausal women |journal=The Journal of Nutrition|date=Nov 2009|volume=139|issue=11|pages=2037–43|pmid=19776178|doi=10.3945/jn.109.110874|doi-access=free}}</ref>
The percent fractional elimination of (''S'')-equol in urine after oral administration is high and in some adults can reach close to 100 percent. The percent fractional elimination of daidzein is much lower at 30 to 40 percent.<ref>{{cite journal|last=Setchell|first=KD|author2=Clerici, C |title=Equol: pharmacokinetics and biological actions |journal=The Journal of Nutrition|date=Jul 2010|volume=140|issue=7|pages=1363S–8S|pmid=20519411|doi=10.3945/jn.109.119784|pmc=2884334}}</ref>