Different inhibition properties of catechins on the individual subunits of mucosal α-glucosidases as measured by partially-purified rat intestinal extract

Mucosal α-glucosidases from rat intestinal powder were employed, with a step to remove α-amylase, to measure the possibility of different inhibition of catechins, particularly those found in tea, on the four α-glucosidase enzymes. Inhibition of catechins was investigated for the slowing of digestion of glycemic carbohydrates, thus regulating glucose release and absorption. The α-glucosidases were fractionated using size-exclusion chromatography. The partially purified fractions showed higher α-glucosidase activity without any α-amylase activity. Catechins had selective inhibition properties on the α-glucosidases. In particular, (-)-epigallocatechin gallate (EGCG) and (-)-epicatechin gallate (ECG) showed comparably high inhibitory effect on all four individual α-glucosidases, while (-)-epicatechin (EC), and (+)-catechin (C) indicated a more discriminating effect with relatively higher inhibitory effects on sucrase-isomaltase. The findings suggest that catechins differently inhibit the individual subunits of the α-glucosidases, and that they could modulate postprandial blood glucose levels through slowing digestion rate of starch and other glycemic carbohydrates, including sucrose.