First evidences of interaction between pyranoanthocyanins and salivary proline-rich proteins

- Pyranoanthocyanins interact significantly with saliva acidic proline-rich proteins.
- The presence of epicatechin unit into pyranoanthocyanins increase the interaction.
- Pyranoanthocyanins could actively contribute to red wine global astringency.

The contribution of other classes of polyphenol compounds besides tannins to the overall perception of astringency is still poorly understood. So, this work aimed to study the interaction between a family of salivary proline-rich proteins (aPRPs) and representative pyranoanthocyanins in red wines [pyranomalvidin-3-glucoside (vitisin B), pyranomalvidin-3-glucoside-catechol, and pyranomalvidin-3-glucoside-epicatechin] using saturation transfer difference-NMR and MALDI-TOF.For vitisin B KD was of 1.74 mM; for pyranomalvidin-3-glucoside-catechol was 1.17 mM and for pyranomalvidin-3-glucoside-epicatechin it was 0.87 mM. The presence of the flavanol structural unit in the pyranoanthocyanins led to an increase in their interaction with aPRPs. Further, it is also interesting that the values obtained were in the range of KD obtained previously reported for the interaction between the human saliva proline-rich peptides (IB714 and IB937) and procyanidins. Overall, the results obtained suggest that, along with tannins, other polyphenols present in red wine, namely pyranoanthocyanins, could actively contribute to red wine global astringency.