title: Biotransformation of the chemopreventive agent 2',4',4-trihydroxychalcone (isoliquiritigenin) by UDP-glucuronosyltransferases.
abstract: 2',4',4-trihydroxychalcone (isoliquiritigenin), a chalcone found in licorice root and shallots, exhibits antioxidant, estrogenic, and antitumor activities. To complement our previous studies concerning the phase 1 metabolism of isoliquiritigenin, the phase 2 transformation of isoliquiritigenin by human hepatocytes and pooled human liver microsomes (HLMs) was investigated using liquid chromatography/tandem mass spectrometry and UV absorbance. Five glucuronides were detected corresponding to monoglucuronides of isoliquiritigenin and liquiritigenin, but no sulfate conjugates were observed. The UDP-glucuronosyltransferases (UGTs) involved in the formation of the major glucuronide conjugates were identified using recombinant human UGTs in combination with liquid chromatography/mass spectrometry. UGT1A1 and UGT1A9 were the major enzymes responsible for the formation of the most abundant conjugate, isoliquiritigenin 4'-O-glucuronide (MG5), with Km values of 4.30+/-0.47 and 3.15+/-0.24 microM, respectively. UGT1A1 and UGT1A10 converted isoliquiritigenin to the next most abundant phase 2 metabolite, isoliquiritigenin 2'-O-glucuronide (MG4), with Km values of 2.98+/-0.8 and 25.8+/-1.3 microM, respectively. In addition, isoliquiritigenin glucuronides MG4 and MG5 were formed by pooled human intestine and kidney microsomes, respectively. Based on the in vitro determination of a 25.3-min half-life for isoliquiritigenin when incubated with HLMs, the intrinsic clearance of isoliquiritigenin was estimated to be 36.4 ml/min/kg. These studies indicate that isoliquiritigenin will be conjugated rapidly in the liver to form up to five monoglucuronides.
authors.affiliation: Department of Medicinal Chemistry and Pharmacognosy, University of Illinois College of Pharmacy, 833 S. Wood St., Chicago, IL 60612-7231, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Guo
authors.forename: Ang
authors.initials: A
authors.lastname: Liu
authors.forename: Hongmei
authors.initials: H
authors.lastname: Cao
authors.forename: Yan
authors.initials: Y
authors.lastname: Luo
authors.forename: John M
authors.initials: JM
authors.lastname: Pezzuto
authors.forename: Richard B
authors.initials: RB
authors.lastname: van Breemen
mesh_terms: D000449:Aldehyde Reductase / Q000037:antagonists & inhibitors*; D016588:Anticarcinogenic Agents / Q000493:pharmacokinetics*; D001711:Biotransformation; D047188:Chalcones / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics*; D014453:Glucuronosyltransferase / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000201:enzymology; D008099:Liver / Q000201:enzymology; D013058:Mass Spectrometry; D008861:Microsomes / Q000201:enzymology; D013056:Spectrophotometry, Ultraviolet
chemical_list: D016588:Anticarcinogenic Agents; D047188:Chalcones; D004791:Enzyme Inhibitors; C040920:isoliquiritigenin; D000449:Aldehyde Reductase; D014453:Glucuronosyltransferase