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 μM, 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 μM, 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.
Footnotes
-
This research was supported by Grant P01 CA48112 from the National Cancer Institute.
-
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
-
doi:10.1124/dmd.108.021857.
-
ABBREVIATIONS: isoliquiritigenin, 2,4,4′-trihydroxychalcone; HLM, human liver microsome; UGT, UDP-glucuronosyltransferase; HPLC, high-performance liquid chromatography; HPLC/UV, high-performance liquid chromatography with UV absorbance detection; LC/MS, liquid chromatography/mass spectrometry; P450, cytochrome P450; LC/MS/MS, liquid chromatography/tandem mass spectrometry; UDPGA, UDP-glucuronic acid; MG4, isoliquiritigenin 2′-O-glucuronide; MG5, isoliquiritigenin 4′-O-glucuronide; MG1, liquiritigenin 4- or 4′-O-glucuronide; MG2, liquiritigenin 4 or 4′-O-glucuronide; MG3, isoliquiritigenin 4-O-glucuronide.
- Received April 10, 2008.
- Accepted July 23, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
DMD articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|