Abstract
Abstract 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.
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