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  • Title: Use of isoform-specific UGT metabolism to determine and describe rates and profiles of glucuronidation of wogonin and oroxylin A by human liver and intestinal microsomes.
    Author: Zhou Q, Zheng Z, Xia B, Tang L, Lv C, Liu W, Liu Z, Hu M.
    Journal: Pharm Res; 2010 Aug; 27(8):1568-83. PubMed ID: 20411407.
    Abstract:
    PURPOSES: Glucuronidation via UDP-glucuronosyltransferases (or UGTs) is a major metabolic pathway. The purposes of this study are to determine the UGT-isoform-specific metabolic fingerprint (or GSMF) of wogonin and oroxylin A, and to use isoform-specific metabolism rates and kinetics to determine and describe their glucuronidation behaviors in tissue microsomes. METHODS: In vitro glucuronidation rates and profiles were measured using expressed UGTs and human intestinal and liver microsomes. RESULTS: GSMF experiments indicated that both flavonoids were metabolized mainly by UGT1As, with major contributions from UGT1A3 and UGT1A7-1A10. Isoform-specific metabolism showed that kinetic profiles obtained using expressed UGT1A3 and UGT1A7-1A10 could fit to known kinetic models. Glucuronidation of both flavonoids in human intestinal and liver microsomes followed simple Michaelis-Menten kinetics. A comparison of the kinetic parameters and profiles suggests that UGT1A9 is likely the main isoform responsible for liver metabolism. In contrast, a combination of UGT1As with a major contribution from UGT1A10 contributed to their intestinal metabolism. Correlation studies clearly showed that UGT isoform-specific metabolism could describe their metabolism rates and profiles in human liver and intestinal microsomes. CONCLUSION: GSMF and isoform-specific metabolism profiles can determine and describe glucuronidation rates and profiles in human tissue microsomes.
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