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Table 3 Effects of pH on tannin-PRP solubility

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

Reference

Method

Tannin type

pH

Effect

[61]

Diffusion precipitation interaction assay

Hydrolyzable and condensed wine extracts, catechin, tartaric acid, gallic acid

3.5 vs. 7.0

↓pH ↑precipitation

[62]

Competitive binding assay

Quebracho and tannic acid

2.0 vs. 7.4

↓pH ↑precipitation

[52]

In vitro digestion precipitation interaction assay, HPLC, SDS-PAGE

EgCG

2.07, 7.8, 5.0–9.0

↓pH + ↑ tannin = enzyme inhibition, blunted by PRP

[59]

NMR

Galloyl rings from tannic acid

3.5 vs. 1.7

↓pH ↑precipitation

[63]

SDS PAGE

Wine or tannic acid

2.9, 3.0, 3.6

↓pH ↓solubility of tannin-PRP

  1. NMR Nuclear magnetic resonance imaging, SDS-PAGE sodium dodecyl polyacrylamide gel electrophoresis, HPLC high performance liquid chromatography, EgCG epigallocatechin gallate, PRP proline rich protein