Separation of grape and wine proanthocyanidins according to their degree of polymerization

A method was developed for the fractionation of grape and wine proanthocyanidins according to their degree of polymerization. The grape and wine proanthocyanidins were fractionated on C-18 Sep-Pak cartridges into three fractions by different organic solvents. The combination of TLC analytic HPLC, and degradation with toluene-alpha-thiol confirmed that these three fractions contained, respectively, monomeric flavan-3-ols (catechins), oligomeric proanthocyanidins, and polymeric proanthocyanidins. The mean degrees of polymerization for oligomeric and polymeric proanthocyanidins in red wine were, respectively, 4.8 and 22.1, and those in the seed extract, 9.8 and 31.5. The method proposed is very interesting for the study of grape and wine proanthocyanidins according to their degree of polymerization, and a further quantification is also possible.