Table 2 Effects of tannin, PRP concentration on binding
From: Salivary proline-rich protein may reduce tannin-iron chelation: a systematic narrative review
Reference | Method | Tannin type | PAC-TA comparison | Conditions of assay | Outcome | Concentration effect |
|---|---|---|---|---|---|---|
[53] | DLS | PAC as tetramers, pentamers, gallates | No | 31.2 mg/L GSE: 0.5–5 mg/L IB-8c or 3.12 mg/L IB-8c: 19.5–46.8 mg/L GSE; pH 5.0, 12% ethanol | Increase in PRP concentration increases aggregation and precipitation of tannins to a maxima, then increased protein concentrations favors dissociation due to reductions in tannin-cross linking | Tannin stacking and crosslinking at higher concentrations |
[55] | SDS-PAGE, HPLC, tryptic digestion | PAC as dimers, trimers, tetramers | No | 0.00–1.5 mM GSE in saliva; pH 5.0, 12% ETOH | At higher tannin concentrations, less PRP are required for similar binding at lower tannin concentrations. | Tannin stacking and crosslinking at higher concentrations |
[56] | ESI-MS | EgCG, ECG, B2, B2 3-O gallate, reserpine | No | 1:10 ratio protein: polyphenol; pHÂ 3.2 | Higher tannin concentration of tannins favor tannin-PRP stability in gastric digestion | Stability of tannin-PRP binding |
[51] | ESI-MS; DLS,SAXS | EgCG | No | 0.336 mM (1–3.5 mg/ml) PRP (IB5); 2:1 protein: polyphenol; pH 5.5 | At lower concentrations, PRP are bound to tannins, but soluble. At higher concentrations, more tannin is needed to effectively bind the same amount of PRP; this happens as binding occurs regardless of proline terminal residue numbers. | Tannin stacking and crosslinking at higher concentrations |
[57] | HPLC-DAD | PAC as monomers, dimers, trimers | No | 1–8 ml saliva mixed with 40 ml GSE or 20 or 40 ml sipped | Increased tannin concentration increases precipitation. | Tannin stacking and crosslinking at higher concentrations |
[58] | ITC | GSE as catechin, epicatechin, epicatechin 3-O gallate | No | 5–25 μg PAC and 40 μl saliva with 10% ethanol | Increased tannin concentration increases precipitation. | Tannin stacking and crosslinking at higher concentrations |
[47] | NMR, DLS | EgCG, EGC, PGG | Yes | 20Â mM polyphenol with 2Â mM mouse PRP; pHÂ 3.8 | The number of PRP binding sites does not correlate with the corresponding decrease in tannin concentration after tannin-PRP binding at higher concentrations | Tannin stacking and crosslinking at higher concentrations |
[59] | NMR | Tannic acid | No | 1:0–1:5.6 ratio of PRP to tannic acid | More tannin-PRP complexes that are bound, the less that the complexes dissociate | Stability of tannin-PRP binding |