Lowering effect of combined sweet potato and onion intake on plasma quercetin concentration and underlying mechanism involving intestinal ß-glucosidase activity.

A combined intake of cooked sweet potato and fried onion in humans was found to suppress the increase of plasma quercetin metabolite concentration. Experiments using rat ß-glucosidase indicated that excess carbohydrate digestion products, especially glucose-containing saccharides, interfere with the deglycosylation of quercetin glucosides during intestinal epithelial uptake. Combined meals of sweet potato and onion may lower the bioavailability of onion quercetin glucosides.