PT  - JOURNAL ARTICLE
AU  - Stephen W. J. Wang
AU  - Jun Chen
AU  - Xiaobin Jia
AU  - Vincent H. Tam
AU  - Ming Hu
TI  - Disposition of Flavonoids via Enteric Recycling: Structural Effects and Lack of Correlations between in Vitro and in Situ Metabolic Properties
AID  - 10.1124/dmd.106.009910
DP  - 2006 Nov 01
TA  - Drug Metabolism and Disposition
PG  - 1837--1848
VI  - 34
IP  - 11
4099  - http://dmd.aspetjournals.org/content/34/11/1837.short
4100  - http://dmd.aspetjournals.org/content/34/11/1837.full
SO  - Drug Metab Dispos2006 Nov 01; 34
AB  - The purpose of this study is to determine the importance of coupling of efflux transporters and metabolic enzymes in the intestinal disposition of six isoflavones (genistein, daidzein, formononetin, glycitein, biochanin A, and prunetin), and to determine how isoflavone structural differences affect the intestinal disposition. A rat intestinal perfusion model was used, together with rat intestinal and liver microsomes. In the intestinal perfusion model, significant absorption and excretion differences were found between isoflavones and their respective glucuronides (p <0.05), with prunetin being the most rapidly absorbed and formononetin glucuronides being the most excreted in the small intestine. In contrast, glucuronides were excreted very little in the colon. In an attempt to account for the differences, we measured the glucuronidation rates of six isoflavones in microsomes prepared from rat intestine and liver. Using multiple regression analysis, intrinsic clearance (CLint) and other enzyme kinetic parameters (Vmax and Km) were determined using appropriate kinetic models based on Akaike's information criterion. The kinetic parameters were dependent on the isoflavone used and the types of microsomes. To determine how metabolite excretion rates are controlled, we plotted excretion rates versus calculated microsomal rates (at 10 μM), CLint values, Km values, or Vmax values, and the results indicated that excretion rates were not controlled by any of the kinetic parameters. In conclusion, coupling of intestinal metabolic enzymes and efflux transporters affects the intestinal disposition of isoflavones, and structural differences of isoflavones, such as having methoxyl groups, significantly influenced their intestinal disposition. The American Society for Pharmacology and Experimental Therapeutics