Gallated Form of Tea Catechin, Not Nongallated Form, Increases Fecal Starch Excretion in Rats

• Published in: Journal of Nutritional Science and Vitaminology 2012, Vol.58(1), pp.45-49
• Main Authors: UNNO, Tomonori, MATSUMOTO, Yoshimi, YAMAMOTO, Yukari
• Format: Article
• Language: English
• Subjects: (−)-epigallocatechin; (−)-epigallocatechin gallate; apparent digestibility; Biological and medical sciences; Feeding. Feeding behavior; Fundamental and applied biological sciences. Psychology; starch; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0301-4800; 1881-7742
• DOI: 10.3177/jnsv.58.45

This study was carried out to elucidate the structural advantage of a gallated form of tea catechin on modulating bioavailability of dietary starch in rats. Animal studies demonstrated that the addition of 0.5% (w/w) (−)-epigallocatechin gallate (EGCG) to the diet brought about a significant increase in the starch content in the feces collected for 2 d at the fourth week of feeding over that with the control diet. Of the gross starch that the rats consumed from their respective diets during the fecal collection period, 0.1% (for control diet) and 1.9% (for EGCG diet) were estimated to be excreted in the feces. However, such a significant increase in the fecal excretion of starch by the EGCG diet was lost by undergoing hydrolysis of EGCG to (−)-epigallocatechin (EGC) and gallic acid (GA). In vitro investigation also showed that EGCG inhibited porcine pancreatic α-amylase activity in a concentration-dependent fashion, whereas the hydrolyzed preparation (the mixture of EGC and GA) exhibited a lack of the inhibitory activity for α-amylase. The modification of dietary starch digestion by inhibiting intestinal α-amylase activity with EGCG may be responsible at least in part for increasing fecal output of starch in rats. Thus, the attachment of a galloyl moiety to the tea flavan-3-ol skeleton may be of key importance for reducing intestinal digestion of dietary starch in rats.