Abstract
The digestive enzymes–polyphenolic compounds (PCs) interactions behind the inhibition of these enzymes have not been completely studied. The existing studies have mainly analyzed polyphenolic extracts and reported inhibition percentages of catalytic activities determined by UV-Vis spectroscopy techniques. Recently, pure PCs and new methods such as isothermal titration calorimetry and circular dichroism have been applied to describe these interactions. The present review focuses on PCs structural characteristics behind the inhibition of digestive enzymes, and progress of the used methods. Some characteristics such as molecular weight, number and position of substitution, and glycosylation of flavonoids seem to be related to the inhibitory effect of PCs; also, this effect seems to be different for carbohydrate-hydrolyzing enzymes and proteases. The digestive enzyme–PCs molecular interactions have shown that non-covalent binding, mostly by van der Waals forces, hydrogen binding, hydrophobic binding, and other electrostatic forces regulate them. These interactions were mainly associated to non-competitive type inhibitions of the enzymatic activities. The present review emphasizes on the digestive enzymes such as α-glycosidase (AG), α-amylase (PA), lipase (PL), pepsin (PE), trypsin (TP), and chymotrypsin (CT). Existing studies conducted in vitro allow one to elucidate the characteristics of the structure–function relationships, where differences between the structures of PCs might be the reason for different in vivo effects.
Highlights
Polyphenolic compounds (PCs) are plant secondary metabolites that are involved in functions such as defense against predators, protection against UV light damage and environmental stress or reproduction, among others [1]
Employed in vitro techniques can provide excellent data regarding PCs–enzyme interactions, but it seems that novel in silico approaches will be the step to complete these studies, before in vivo assessments
The non-covalent interactions are the key of the enzymatic inhibition, because these interactions are the basis of reversible inhibitions that may result potentially convenient for certain medical therapies
Summary
Polyphenolic compounds (PCs) are plant secondary metabolites that are involved in functions such as defense against predators, protection against UV light damage and environmental stress or reproduction, among others [1]. PCs can be classified as phenolic acids, flavonoids, tannins, stilbenes, curcuminoids, lignans, and others [1,2,3]. The largest groups of PCs are the phenolic acids, flavonoids and tannins (see Figure 1 for examples). Phenolic acids, which possess one aromatic ring and at least one carboxylic acid moiety in their structure, are divided into two groups, hydroxybenzoic acids (C6-C1) (i.e., gallic acid) and hydroxycinnamic acids (C6-C3) (i.e., p-coumaric acid). The flavonoids exhibit a three ring structure base (C6-C3-C6), and are divided in several subgroups such as flavones, flavonols, flavanones, flavanols and others [4], depending on the substitutions in the central heterocyclic ring, while tannins are polymeric PCs with higher molecular weights, that can be divided into two subgroups, hydrolyzable tannins and condensed tannins, such as ellagitannins and proanthocyanidins, respectively [5].
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