Digestive stability and transport of equol by Caco-2 cells
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Date
2006-04-17T13:48:08Z
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Abstract
Equol has been reported to have greater estrogenic and antioxidant activity than daidzein, its isoflavonoid precursor in soy. However, only 30 - 50% of humans have intestinal microflora capable of converting daidzein to equol. We questioned whether dietary supplementation of equol represents a strategy to provide all individuals with its proposed benefits. Stability and bioaccessibility during simulated digestion, as well as uptake, transepithelial transport and efflux of equol by Caco-2 cells, were examined. Recovery of equol following digestion was 106% ± 6% with ≥ 93% partitioning into the aqueous fraction of chyme. Caco-2 cells were grown on culture dishes and transwell inserts to characterize uptake and transepithelial transport of equol, respectively. After 4 h, cellular equol content was proportional to the concentration in medium, and represented only 5 to 7% of the starting amount. Maximum cellular accumulation of equol occurred within 1 h and declined with increasing length of exposure. Decreases in cellular equol were associated with excretion of phase II conjugates across the apical and basolateral membranes. By 4 h, 85% of equol in cultures was present as phase II conjugates with 50 and 35% of the starting amount located in the apical and basolateral compartments, respectively. Free equol in the basolateral compartment increased to a maximum within 1 h, but continually declined thereafter. These data suggest that ingested equol has the potential to be absorbed and that individuals classified as “non-producers” may actually efflux equol conjugates into the intestinal lumen with high efficiency.
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equol, digestive stability, transepithelial transport, bioaccessibility