Phloretin-like action of bioflavonoids on sugar accumulation capability of isolated intestinal cells

Flavanones and flavones are structural analogues of phloretin. Like phloretin they inhibit the non-Na+-dependent, facilitated diffusion transport system for sugars associated with the lateral serosal boundary of intestinal epithelial cells. The degree of inhibition varies with the extent and position of hydroxylation of the flavonoid nucleus. Flavones are more potent than corresponding flavanones. Tri- and tetrahydroxylated forms are more inhibitory than similar penta- and hexahydroxylated molecules. With one exception, none of the 18 flavonoids tested has secondary effects as metabolic inhibitors, as does phloretin. Inhibition of the passive sugar transport system with flavonoids allows the concentrative Na+-dependent sugar transport system to establish a better concentration gradient than is observed in untreated cells. The degree of gradient enhancement is proportional to the degree of inhibition of the sugar "leak." The flavonoid glycosides, which can be considered as phlorizin analogues, also inhibit the non-Na+-dependent sugar carrier, but less well than corresponding nonglycosylated agents. Only one of the glycosides inhibits the Na+-dependent transport system, and much less potently than phlorizin.