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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