The effect of pectic polysaccharides from grape skins on salivary protein - procyanidin interactions

Abstract

In this study, water and chelator-soluble pectic polysaccharide fractions were obtained from white grape skins, aiming to study their impact on the interaction between low polymerized grape seed procyanidins and salivary proteins. Water and chelator-soluble polysaccharide fractions were composed by uronic acids and neutral sugars, mainly arabinose and galactose, with water polysaccharide fraction showing a higher amount of branched pectic polysaccharides. Both polysaccharide fractions were able to mitigate salivary protein-procyanidin interactions, by a competition mechanism, resulting in a decrease of the amount of precipitated protein. Water polysaccharide fraction was the most effective in inhibiting salivary protein precipitation, especially for acidic proline-rich proteins, due to the higher affinity to interact with procyanidins (K_A = 22222 M^-1 and K_A = 365 M^-1 for water and chelator polysaccharides, respectively). The interaction between polysaccharides and procyanidins showed to be mainly governed by hydrophobic effect.

Keywords: Astringency; Pectin; Procyanidins; Salivary proteins.