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Title: Dietary phenolic compounds selectively inhibit the individual subunits of maltase-glucoamylase and sucrase-isomaltase with the potential of modulating glucose release

Author
item SIMSEK, MERIC - Purdue University
item QUEZADA-CALVILLO, ROBERTO - Children'S Nutrition Research Center (CNRC)
item FERRUZZI, MARIO - Purdue University
item NICHOLS, BUFORD - Children'S Nutrition Research Center (CNRC)
item HAMAKER, BRUCE - Purdue University

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2015
Publication Date: 3/30/2015
Citation: Simsek, M., Quezada-Calvillo, R., Ferruzzi, M.G., Nichols, B.L., Hamaker, B.R. 2015. Dietary phenolic compounds selectively inhibit the individual subunits of maltase-glucoamylase and sucrase-isomaltase with the potential of modulating glucose release. Journal of Agricultural and Food Chemistry. 63(15):3873-3879.

Interpretive Summary: There is very little free glucose in the human diet. Four intestinal surface enzyme activities digest glucose chains in food starch and starch fragments to free glucose. There are more than 400 plant compounds which are known to inhibit starch digestion to glucose. We studied four of these compounds using our four pure surface enzymes. Selective blockers of the fast-digesting surface enzymes by the plant compounds were found. Diets including these selective blockers could lead to a slow digestion of food starch for improved blood glucose levels after meals.

Technical Abstract: In this study, it was hypothesized that dietary phenolic compounds selectively inhibit the individual C- and N-terminal (Ct, Nt) subunits of the two small intestinal alpha-glucosidases, maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI), for a modulated glycemic carbohydrate digestion. The inhibition by chlorogenic acid, caffeic acid, gallic acid, (+)-catechin, and (-)-epigallocatechin gallate (EGCG) on individual recombinant human Nt-MGAM and Nt-SI and on mouse Ct-MGAM and Ct-SI was assayed using maltose as the substrate. Inhibition constants, inhibition mechanisms, and IC[50] values for each combination of phenolic compound and enzymatic subunit were determined. EGCG and chlorogenic acid were found to be more potent inhibitors for selectively inhibiting the two subunits with highest activity, Ct-MGAM and Ct-SI. All compounds displayed noncompetitive type inhibition. Inhibition of fast-digesting Ct-MGAM and Ct-SI by EGCG and chlorogenic acid could lead to a slow, but complete, digestion of starch for improved glycemic response of starchy foods with potential health benefit.