Salivary proline-rich protein may reduce tannin-iron chelation: a systematic narrative review

Nutrition & Metabolism

Table 5 PRP binding to hydrolyzable vs. condensed tannins

Reference	Method	Tannin type	Bond stability	Binding affinity
[66]	Competitive binding assay	5GG, gallic acid, EGC	nd	Hydrolyzable tannin > condensed tannin
[62]	Competitive binding assay	Quebracho and tannic acid	Hydrolyzable: 20% greater dissolution of bonds in gastric and enteric digestion	Hydrolyzable tannin > condensed tannin
[48]	NMR	B2, PGG, TGG, PAC monomer	Hydrogen bonds associated with hydrolyzable tannins	B2 > PGG > TGG>
[47]	NMR, DLS	EgCG, EGC, PGG	Hydrogen bonds associated with hydrolyzable tannins	Hydrolyzable tannin > condensed tannin
[63]	SDS PAGE	Wine or tannic acid	Condensed tannins associated with hydrophobic bonds	nd
[61]	HPLC	Hydrolyzable vs. condensed wine extracts	nd	Increased precipitation of condensed tannin at pH 7.5 c/t hydrolyzable tannin

NMR Nuclear magnetic resonance imaging, DLS dynamic light scattering, SDS-PAGE sodium dodecyl polyacrylamide gel electrophoresis, HPLC high performance liquid chromatography. B2: proanthocyanidin B2, PGG pentagalloylglucose, TGG tetragalloylglucose, PAC proanthocyanidin, EgCG epigallocatechin gallate, ECG epigallocatechin, PRP proline rich protein. nd = not determined

ISSN: 1743-7075