Tea polyphenols: Enzyme inhibition effect and starch digestibility

Abstract

Slowly digestible starch (SDS) offers a range of health benefits due to its stabilizing and sustaining effect on blood glucose. Contributors to the slow digestion property of certain starches include their specific structure and their interaction with factors that inhibit effective digestion. In this study, the effects of tea polyphenols (TPLs) on the enzyme activities of pancreatic a-amylase and amyloglucosidase, which are used during starch digestion, were investigated by an in vitro Englyst test. Our results showed that TPLs noncompetitively inhibit the activity of pancreatic a-amylase (pH 6.9) but activate amyloglucosidase (pH 4.6) in a dose-dependent manner. However, when the two enzymes were employed together under the Englyst test condition at pH 5.2, a heterogeneous inhibition pattern was observed with a peak inhibition of $30% when the TPL content was $2.5 mg/mL, and a negative inhibition pattern when TPL content was greater than 4 mg/mL. In contrast, a similar degree of starch digestibility was observed in the presence of TPLs, which indicates that a modification of the Englyst assay warrants further studies to reflect the in vivo starch-digestion patterns, where a slower digestion of starch was observed in the presence of TPLs, which is corroborated by in vivo studies from the literature.

Polyphenolic inhibition of enterocytic starch digestion enzymes and glucose transporters for managing type 2 diabetes may be reduced in food systems

“…Evidence has shown that pure polyphenols and phenolic extracts from different sources have inhibitory activities against α-amylase and α-glucosidase ( Sun and Miao, 2019 ; Yilmazer-Musa et al., 2012 ; Sun et al., 2016 ). Through in vitro studies, diverse sources of phenolics such as gallic acid, tea phenolic extracts and blue maize anthocyanins have also been reported to slow starch digestion ( Guzar et al., 2012 ; Camelo-mendez et al., 2016 ; Lv et al., 2019 ; Peng et al., 2016 ). In a study on the effect of Mexican blue maize anthocyanins on starch digestibility, Camelo-Mendez et al.…”

Effect of Tea/Tea Extracts on α‐Glucan Hydrolysis by Enzymes In Vitro and In Vivo − With Parallel Impacts on Health

“…Earlier work by these authors showed that ‘…green, oolong and black tea extracts, epigallocatechin gallate, theaflavin‐3, 3′‐digallate and tannic acid were competitive inhibitors (i.e., compete for the active site of the enzyme) of porcine pancreatic α‐amylase, whereas epicatechin gallate, theaflavin‐3′‐gallate and theaflavin were mixed‐type inhibitors with both competitive and uncompetitive (i.e ., interacting with the enzyme during enzyme‐substrate interaction) inhibitory characteristics. Only catechins with a galloyl substituent at the 3‐position showed measurable inhibition.’ Peng et al also reported that tea polyphenols non‐competitively inhibit (i.e., interacting with the enzyme outside the active site) the activity of pancreatic α‐amylase (although they may activate amyloglucosidase depending on conditions employed). Readers are referred to Table for a detailed overview of tea/tea extract interactions with digestive enzymes.…”