Gallic acid inhibits brush border disaccharidases in mammalian intestine

Intestinal epithelium constitutes the primary target tissue for interaction with dietary micronutrients. The objective of this study was to determine if gallic acid, a polyphenol that is an important constituent of various edible plant-based foods, affects brush border disaccharidases in mammalian intestine. In this investigation, we found that 0.05 to 0.6 mmol/L gallic acid inhibited sucrase activity by 34% to 86%. Optimum enzyme inhibition was observed at 0.4-mmol/L gallic acid concentration, which was 82% in the rat, 83% in LACA/L mice, 50% in BALB/c mice, and 28% in rabbit intestine. The observed enzyme inhibition was reversible in rat intestines. Gallic acid also depressed the activities of maltase (42%), trehalase (45%), and lactase (13%) in the rat. Inhibition of sucrase activity by gallic acid was mainly between pH 4.8 to 7.2, whereas at alkaline pH (7.7-8.5), gallic acid stimulated enzyme activity by 20% to 30% in both rat and rabbit intestines. Kinetic analysis revealed that gallic acid was a fully competitive inhibitor of rat sucrase at pH 5.5 and 6.8. The effect of gallic acid together with various -SH group–reacting reagents showed that the observed inhibition was additive in nature. Similar results were obtained in the presence of 0.4 mmol/L gallic acid and 4 mmol/L harmaline, a plant alkaloid. These findings suggest that gallic acid is a potent inhibitor of brush border sucrase and other disaccharidases and thus could potentially interfere with the digestive functions of the intestine.