Bioavailability of genistein and its glycoside genistin as measured in the portal vein of freely moving unanesthetized rats.

The present study describes an in vivo bioavailability experiment for genistein and its glycoside genistin, either as pure compounds or from a soy protein isolate extract, using freely moving unanesthetized rats with a cannulation in the portal vein. The results show that genistein is readily bioavailable, being observed in portal vein plasma at the first point of detection at 15 min after dosing. The AUC(0-24h) values for total genistein and its conjugates were 54, 24, and 13 microM h for genistein, genistin, and an enriched protein soy extract, respectively.

The type of sugar moiety is a major determinant of the small intestinal uptake and subsequent biliary excretion of dietary quercetin glycosides.

Quercetin is an important dietary flavonoid with putative beneficial effects in the prevention of cancer and CVD. The in vivo bioactivity of quercetin depends on its bioavailability, which varies widely between foods. We used an in situ rat intestinal perfusion model to study whether differential small intestinal hydrolysis of the sugar moiety of five naturally occurring quercetin glycosides determines the small intestinal uptake and subsequent biliary excretion of quercetin.

Intestinal uptake of quercetin-3-glucoside in rats involves hydrolysis by lactase phlorizin hydrolase.

Quercetin has antioxidant, anti-inflammatory, antiproliferative and anticarcinogenic properties. In plant foods, quercetin occurs mainly bound to various sugars via a beta-glycosidic link. We hypothesized that lactase phlorizin hydrolase (LPH), an enzyme at the brush border membrane of intestinal cells, is involved in the in vivo intestinal uptake of quercetin-sugars.