This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.Purpose of Aim 4- Pharmacokinetics of equol enantiomers Equol is produced in the intestine by bacteria from daidzein, an isoflavone found in abundance in soy foods. Equol occurs in 2 chemical forms called enantiomers (mirror images), and termed R-equol and S-equol. Little is known about the synthesis, metabolism or pharmacokinetics of these two equol enantiomers in humans, but both have unique biological properties. This proposed study will determine the bioavailability and pharmacokinetics of R-equol and S-equol and of a racemic mixture (1:1 ratio) of these two enantiomers. This will be done by measuring the appearance and disappearance of equol in plasma and urine after administering a single oral bolus dose of 20mg of each enantiomer and of the racemic mixture. To distinguished the orally administered equol from that naturally present from dietary foods we will administer a stable isotopically labeled form of equol in which one atom of carbon 12 is replaced by one atom of carbon 13. These isotopes are non-radioactive and non-hazardous and will permit us to trace the metabolism and fate of equol accurately. We isolated and purified the stable labeled enantiomers [13C]R-equol and [13C]S-equol for a previous NIH grant and their purity has been verified by HPLC and Mass Spectrometry. The dose chosen is within the normal physiological range of dietary exposure in people consuming soy foods on a daily basis as determined by plasma equol concentrations. Preliminary studies have been performed in three healthy adults using the same dosing level of purified S and R-equol with no adverse effects. This study does not involve using pharmacological doses or dose ranging as typically carried out in pharmacological developments. Rather, these studies are intended to understand the physiology and metabolism of equol enantiomers and are not being performed with any therapeutic intension.
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