title: Structural elucidation of hydroxylated metabolites of the isoflavan equol by gas chromatography-mass spectrometry and high-performance liquid chromatography-mass spectrometry.
abstract: Equol has, as have other isoflavonoids, recently gained considerable interest due to its possible health effects. However, detailed studies on the metabolism of equol are scarce. Therefore, we investigated the phase I metabolism of equol using liver microsomes from Aroclor-treated male Wistar rats as well as from a male human. The identification of the metabolites formed was elucidated using high performance liquid chromatography (HPLC) with diode array detection, HPLC/atmospheric pressure ionization electrospray mass spectrometry, and gas chromatography-mass spectrometry, as well as reference compounds. (+/-)-Equol was converted to 11 metabolites by the liver microsomes from Aroclor-pretreated rats comprising three aromatic monohydroxylated and four aliphatic monohydroxylated as well as four dihydroxylated products. The main metabolite was identified as 3'-hydroxy-equol. Using human liver microsomes, equol was converted to six metabolites with 3'-hydroxy- and 6-hydroxy-equol as main products. Furthermore, the aliphatic hydroxylated metabolite 4-hydroxyequol, which was recently detected in human urine after soy consumption, was formed. On the basis of these findings, it is suggested that phase I metabolism of equol is part of a complex biotransformation of the soy isoflavone daidzein in humans in vivo.
authors.affiliation: Institute of Nutritional Physiology, Federal Research Center for Nutrition and Food, Karlsruhe, Germany.
authors.forename: Corinna E
authors.initials: CE
authors.lastname: Rüfer
authors.forename: Hansruedi
authors.initials: H
authors.lastname: Glatt
authors.forename: Sabine E
authors.initials: SE
authors.lastname: Kulling
mesh_terms: D000818:Animals; D001140:Aroclors / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D060754:Equol; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006801:Humans; D006900:Hydroxylation; D007529:Isoflavones / Q000737:chemistry* / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D015394:Molecular Structure; D051381:Rats; D017208:Rats, Wistar; D013237:Stereoisomerism
chemical_list: C007610:4',7-dihydroxy-3,4-dihydroisoflavone; D001140:Aroclors; D007529:Isoflavones; D060754:Equol