Evaluation of chlorogenic acids and melanoidin interactions with salivary proteins and their effect on tooth discoloration

Tooth discoloration is a multifactorial process that is significantly influenced by the interaction between dietary polyphenols and salivary proteins. This study investigates coffee-induced discoloration using in vitro staining models and in silico simulations.

For 14 days, human premolar teeth were soaked in coffee solution (27 g/450 mL) with daily replacement. Lab and ΔE measurements were used to quantify color changes before and after immersion using ultraviolet-visible spectroscopy. Melanoidin compounds docked with salivary proteins (statherin, histatin, and proline-rich protein [PRP]). Hex 8.0 was used for molecular docking, whereas Discovery Studio Visualizer and UCSF Chimera were used for molecular dynamics analysis.

Molecular docking revealed the strong binding affinity of chlorogenic acid with PRP (-251.66 kJ/mol), histatin (-245.4 kJ/mol), and statherin (-240.5 kJ/mol), stabilized by hydrogen bonds with glycine/arginine/tyrosine residues. The molecular dynamics simulations confirmed complex stability with statherin (RMSD 4.2-4.6 Å) and histatin (RMSD 4.4-4.6 Å). Chromameter analysis showed significant color changes after coffee exposure (ΔEab = 12.286 ± 3.645), with a decrease in lightness (L: 83.569 → 71.873) and an increase in redness (a*: 1.375 → 2.992) and yellowness (b*: 15.848 → 18.585). Paired samples correlation analysis revealed statistically significant changes in the a* and b* values (p < 0.001), while the L* value showed no significant change (p = 0.257).

Chlorogenic acid drives discoloration through stable protein interactions and measurable color shifts, suggesting that targeted inhibition of these molecular pathways could prevent coffee-induced discoloration.