The interaction between tannins and gliadin derived peptides in a celiac disease perspective

Given the high prevalence and lack of therapeutic means to treat celiac disease, the search for drugs and nutraceuticals that can block the initial stages of this chronic inflammatory disorder is a priority. Among the diversity of polyphenols, tannins have been described as the most reactive towards proline-rich proteins, which are structurally similar to gliadin peptides responsible for the onset of celiac disease. Therefore, the aim of this work was to verify the ability of different food tannins to interact with gliadin derived peptides, using fluorescence quenching and dynamic light scattering experiments. For that, a commercial raw extract of wheat gliadins was subjected to in vitro digestion followed by fractionation of the partially degraded peptides by semi-preparative HPLC. Each one of the seven collected mixtures were then characterized by ESI-MS/MS to identify their peptide composition. Using procyanidin B3, procyanidin trimers, procyanidin tetramers and an oligomeric mixture of high molecular weight procyanidins it was demonstrated, for the first time, that the association between those tannins and gliadin-derived peptides may occur, although in different contexts. Indeed, at the micromolar level it was observed by means of fluorescence assays that the size and structural features of the polyphenols is related to their quenching ability as a result of specific interactions or complex formation. At the millimolar level by using DLS, it was concluded that the procyanidins reactivity towards different peptide mixtures is mainly dependent on the peptide size with drastic effects on the dimension of the resulting aggregates. Overall, this study clearly opens new therapeutic perspectives for celiac disease, by using phenolic compounds as a nutraceutical approach to enhance the return of the full intestinal function in patients who show incomplete recovery in response to a gluten-free diet.