Forty flavones have been tested for inhibitory activity toward rat small intestinal sucrase and maltase with the object of developing a new type of sugar absorption inhibitor for the treatment of diabetes and obesity. It was suggested that the greater the number of hydroxyl groups, the higher the inhibitory activity. The IC50 values of the two most potent flavones, 3', 4', 5, 6, 7-pentahydroxy-flavone (24, PHF) and 3', 4', 5, 6, 7-pentahydroxy-3-methoxyflavone (27, PHMF), for sucrase were 13 and 28 μM, and those for maltase were 29 and 31 μM. The types of inhibition by PHF and PHMF were both uncompetitive for sucrase and non-competitive for maltase. PHF at 25 mg/kg significantly inhibited the intestinal absorption of sucrose, but not maltose, in rats. These results indicate that PHF (24) and more potent flavones, if they can be found, may be useful clinically.
