Cis-resveratrol glucuronidation kinetics in human and recombinant UGT1A sources.
It was hypothesized that cis-resveratrol glucuronidation contributes to a greater extent to in-vitro disposition of total resveratrol than previously assumed. To this end, the kinetic data for cis-resveratrol glucuronidation are reported. Glucuronidation assays were conducted in human liver and intestinal microsomes and in uridine diphosphate-glucuronosyltransferases (UGTs) UGT1A1, UGT1A6, UGT1A9, and UGT1A10. Kinetic parameters were estimated for the major cis-resveratrol-3-O-glucuronide (cis-R3G). Substrate inhibition was observed with apparent V(max), K(m) and K(i) of 6.1 +/- 0.3/27.2 +/- 1.2 nmol min(-1) mg(-1), 415 +/- 48.1/989.9 +/- 92.8 and 789.6 +/- 76.3/1012 +/- 55.9 microM in human intestinal microsomes (HIMs) and UGT1A6, respectively (estimate +/- standard error (SE)). Biphasic kinetics were observed in human liver microsomes (HLMs), while sigmoidal kinetics were seen in UGT1A9 (V(max) = 11.92 +/- 0.2 nmol min(-1) mg(-1); K(m) = 360 microM; n = 1.27 +/- 0.07). The 4'-O-glucuronide (cis-R4'G) exhibited atypical kinetics in HLM, HIM, UGT1A1, and UGT1A10. UGT1A9 catalysed cis-R4'G formation at high substrate concentrations (V(max) = 0.33 +/- 0.015 nmol min(-1) mg(-1); K(m) = 537.8 +/- 67.8 microM). In conclusion, although the rates of formation of cis-R3G in HLM and UGT1A9 were higher than those for trans-R3G, the contribution to total resveratrol disposition could not be determined fully due to atypical kinetics observed.
Iwuchukwu
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Department of Pharmaceutical Sciences, Temple University School of Pharmacy, 3307 North Broad Street, Philadelphia, PA 19140, USA.
Nagar
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D000975:Antioxidants / Q000378:metabolism*; D014453:Glucuronosyltransferase / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008861:Microsomes / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D000077185:Resveratrol; D013267:Stilbenes / Q000378:metabolism*; D000099148:UGT1A1 Enzyme
D000975:Antioxidants; D014453:Glucuronosyltransferase; D011994:Recombinant Proteins; D000077185:Resveratrol; D013267:Stilbenes; D000099148:UGT1A1 Enzyme