Interaction of Plant Polyphenols with Salivary Proteins

Abstract

Tannins are polyphenols that occur widespread in plant-based food. They are considered to be part of the plant defense system against environmental stressors. Tannins have a number of effects on animals, including growth-rate depression and inhibition of digestive enzymes. Tannins also have an effect on humans: They are, for example, the cause of byssinosis, a condition that is due to exposure to airborne tannin. Their biological effect is related to the great efficiency by which tannins precipitate proteins, an interaction that occurs by hydrophobic forces and hydrogen bonding. Two groups of salivary proteins, proline-rich proteins and histatins, are highly effective precipitators of tannin, and there is evidence that at least proline-rich proteins act as a first line of defense against tannins, perhaps by precipitating tannins in food and preventing their absorption from the alimentary canal. Proline plays an important role in the interaction of proline-rich proteins with tannins. In contrast, it is primarily basic residues that are responsible for the binding of histatins to tannin. The high concentration of tannin-binding proteins in human saliva may be related to the fruit and vegetable diet of human ancestors.

Comparative Evaluation of Various Total Antioxidant Capacity Assays Applied to Phenolic Compounds with the CUPRAC Assay

“…Phenolic derivatives represent the largest group known as 'secondary plant products' synthesized by higher plants, probably as a result of antioxidative strategies adapted in evolution by respirative organisms starting from precursors of cyanobacteria. Many of these phenolic compounds are essential to plant life, e.g., by providing defense against microbial attacks and by making food unpalatable to herbivorous predators [1]. Although a precise chemical definition may be given for plant phenolics, it would inevitably include other structurally similar compounds such as the terpenoid sex hormones.…”

“…These substances contain at least one aromatic ring with one or more attached -OH groups, in addition to other substituents [1], and can be divided into 15 major structural classes [4]. Major classes of plant phenolics with 'the type of carbon skeleton, class name (example)' format include: C 6 , simple phenols (resorcinol); C 6 -C 1 , phenolic acids (p-hydroxybenzoic acid); C 6-C 2 , acetophenones and phenylacetic acids; C 6 -C 3 , hydroxycinnamic acids (caffeic acid); C 6 -C 4 , hydroxyanthraquinones (physcion); C 6 -C 2 -C 6 , stilbenes (resveratrol); C 6 -C 3 -C 6 , flavonoids (quercetin); (C 6 -C 3 ) 2 , lignans (matairesinol); (C 6 -C 3 -C 6 ) 2 , biflavonoids (agathisflavone); (C 6 -C 3 ) n , lignins; (C 6 -C 3 -C 6 ) n , condensed tannins (procyanidin) [2].…”

“…Tannins may be subdivided into hydrolyzable and condensed tannins; the former are esters of gallic acid (gallo-and ellagi-tannins) while the latter are polyhydroxyflavan-3-ols, also known as proanthocyanidins [7]. Bennic [1] defines hydrolyzable tannins consisting of a polyhydric alcohol, such as glucose, to which gallic acid or its dimer hexahydrodiphenic acid are linked in ester linkages, whereas the condensed tannins contain the monomeric unit of a flavan-3-ol such as catechin or epicatechin that is linked through C-C bonds. Basic plant phenolic structures with examples are shown in Figure 1.…”

A poisonous surprise under the coat of the African crested rat

“…Because some mammals' saliva produces proteins that bind to plant polyphenols [17,18], it is possible that Lophiomys salivary secretions are adapted to augment or process ouabain (and possibly other plant toxins) in significant but currently unknown ways, among them enhancement of the toxin's capacity to permeate cells. Among some ouabain-insensitive invertebrates, the location of an ouabain-binding site on the DNA sequence has been narrowed to a single amino acid substitution (asparagine for histidine) at position 122 of Na þ /K þ -ATPase a-subunit gene [19,20].…”

Chromatographic Studies on the Tannins of Aerva lanata (L.) Juss. Ex Schultes

“…Tannins have a characteristic strange smell and astringent taste and could bind through the effective formation of strong complexes with proteins and other macromolecules. Thus, they could have a major impact on animal nutrition, including inhibition of growth rate digestive enzymes [1]. Generally, tannins are classified into hydrolyzable tannins and condensed tannins.…”