Inhibition of α-Amylases by Condensed and Hydrolysable Tannins: Focus on Kinetics and Hypoglycemic Actions

Abstract

The aim of the present study was to compare the in vitro inhibitory effects on the salivary and pancreatic α-amylases and the in vivo hypoglycemic actions of the hydrolysable tannin from Chinese natural gall and the condensed tannin from Acacia mearnsii. The human salivary α-amylase was more strongly inhibited by the hydrolysable than by the condensed tannin, with the concentrations for 50% inhibition (IC50) being 47.0 and 285.4 μM, respectively. The inhibitory capacities of both tannins on the pancreatic α-amylase were also different, with IC50 values being 141.1 μM for the hydrolysable tannin and 248.1 μM for the condensed tannin. The kinetics of the inhibition presented complex patterns in that for both inhibitors more than one molecule can bind simultaneously to either the free enzyme of the substrate-complexed enzyme (parabolic mixed inhibition). Both tannins were able to inhibit the intestinal starch absorption. Inhibition by the hydrolysable tannin was concentration-dependent, with 53% inhibition at the dose of 58.8 μmol/kg and 88% inhibition at the dose of 294 μmol/kg. For the condensed tannin, inhibition was not substantially different for doses between 124.4 μmol/kg (49%) and 620 μmol/kg (57%). It can be concluded that both tannins, but especially the hydrolysable one, could be useful in controlling the postprandial glycemic levels in diabetes.

Effect of Supplementing Hydrolysable Tannins to a Grower–Finisher Diet Containing Divergent PUFA Levels on Growth Performance, Boar Taint Levels in Back Fat and Intestinal Microbiota of Entire Males

“…A possible explanation for these findings is that HTs or their microbial degradation products negatively affected nutrient digestibility and absorption. Recent in vitro studies have revealed that HTs inhibit the pancreatic α-amylase activity and amylase absorption [26]. The current findings on feed efficiency are in agreement with those of previous studies [5,6] although they contradict the findings ofČandek-Potokar et al [4].…”

Dietary polyphenols as antidiabetic agents: Advances and opportunities

“…A study on 36 diabetic Wistar rats revealed that a combination of hydrolysable tannin from Chinese natural gallnuts and condensed tannin from the bark of the black wattle tree ( Acacia mearnsii ) rich in gallotannins and catechins decreased the glycemic levels, which delayed carbohydrate digestion (Kato et al., 2017). The bark of Cinnamomum zeylanicum (a species of cinnamon) rich in tannins and flavonoids inhibited α‐glucosidase and decreased glycemic levels on streptozotocin‐induced diabetic rats due to chronic malabsorption of carbohydrates (Choudhury et al., 2018).…”

Modulatory Effect of Polyphenolic Compounds from the Mangrove Tree Rhizophora mangle L. on Non-Alcoholic Fatty Liver Disease and Insulin Resistance in High-Fat Diet Obese Mice

“…Alpha-amylase assay resulted in the inhibition of AERM activity at an IC 50 of 19.0 µg/mL, while acarbose inhibited amylase with an IC 50 of 5.2 µg/mL ( Figure 8 ). Tannins have been suggested as potent inhibitors of human salivary and porcine pancreatic α-amylases [ 34 , 35 ], suggesting that PAs from AERM could be implicated in this potent inhibitory activity. In addition, it has been reported that PAs of cinnamon water extract inhibited the amyloid formation of Human islet amyloid polypeptide (hIAPP) in a dose-dependent manner.…”