# Investigating the influence of astringent compounds on oral lubrication and the protective role of proline-rich proteins

## TL;DR

This study explores how astringent compounds like tannins affect mouth dryness and how proteins like MUC1 and PRPs help protect oral lubrication.

## Contribution

The study introduces new insights into how MUC1 and proline-rich proteins mitigate the effects of tannins on oral lubrication.

## Key findings

- EgCG disrupts oral lubrication by increasing frictional forces.
- MUC1 reduces tannin effects by preventing aggregation and preserving lubrication.
- PRPs enhance lubrication by binding tannins and limiting mucin interactions.

## Abstract

Astringency, characterized by dryness and roughness in the mouth, is a major challenge for the acceptance of plant-based protein-rich foods. The mechanisms behind this sensation, particularly the role of mucins and the oral epithelium, remain unclear. This study investigates the impact of tannins, specifically epigallocatechin gallate (EgCG), on oral lubrication and examines the role of MUC1 protein in the lubrification and potentially in the astringency perception. The protective effect of proline-rich proteins (PRPs) is also explored. In vitro tribological tests were performed on four oral epithelial models expressing different MUC1 isoforms, using a reconstructed mucosal pellicle. A homemade biotribometer measured friction and dissipated energy to assess tannin-mucin interactions. Results confirm that EgCG disrupts epithelial lubrication, increasing frictional forces. However, MUC1 expression, particularly its structure, reduces these effects by preventing tannin aggregation and preserving lubrication. PRPs also enhance lubrication by binding tannins, limiting their interaction with mucins. This study highlights the roles of MUC1 and PRPs in oral lubrication in the presence of tannins.

The online version contains supplementary material available at 10.1038/s41598-025-29493-2.