Unno Tomonori, Matsumoto Yoshimi, Yamamoto Yukari
Department of Health and Nutrition, Tokyo Kasei Gakuin University, Tokyo, Japan.
J Nutr Sci Vitaminol (Tokyo). 2012;58(1):45-9. 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.
本研究旨在阐明茶儿茶素的没食子酸酯形式在调节大鼠膳食淀粉生物利用度方面的结构优势。动物研究表明，在饲料中添加0.5%（w/w）的（-）-表没食子儿茶素没食子酸酯（EGCG），在喂养第四周时，连续2天收集的粪便中淀粉含量比对照饲料组有显著增加。在粪便收集期间，大鼠从各自饲料中摄入的总淀粉中，估计有0.1%（对照饲料组）和1.9%（EGCG饲料组）随粪便排出。然而，EGCG饮食组粪便中淀粉排泄量的显著增加，在EGCG水解为（-）-表没食子儿茶素（EGC）和没食子酸（GA）后消失。体外研究还表明，EGCG以浓度依赖的方式抑制猪胰α-淀粉酶活性，而水解产物（EGC和GA的混合物）对α-淀粉酶缺乏抑制活性。通过用EGCG抑制肠道α-淀粉酶活性来改变膳食淀粉消化，可能至少部分地导致大鼠粪便中淀粉排出量增加。因此，在茶黄烷-3-醇骨架上连接没食子酰基部分，对于减少大鼠肠道中膳食淀粉的消化可能至关重要。
