| Abstract
| - A method was developed for the fractionation of grape (seed or skin) proanthocyanidins accordingto their degree of polymerization. After precipitation in chloroform/methanol (75:25, v/v), the grapeproanthocyanidins were deposited onto an inert glass powder column and sequentially dissolved inseveral fractions by increasing proportions of methanol in the solvent. Each fraction from eachproanthocyanidin source was quantified and characterized after acidic degradation with phenylmethanethiol (i.e., thiolysis). The comparison of data from total extract and successive fractionsshowed that a quantitative separation was achieved so that estimation of polymer size distributionin relation to other compositional characteristics (proportions of prodelphinidin units, galloylationrate) was thus possible. Mean degree of polymerization of separated proanthocyanidins rangedincreasingly from 4.7 to 17.4 in seed (8.1 for total extract) and from 9.3 to 73.8 in skin (34.9 for totalextract). The method proposed is very interesting for the study of grape proanthocyanidins accordingto their degree of polymerization because it gives both qualitative and quantitative informationespecially on the highly polymerized forms, which were not fractionated by previous techniques. Keywords: Grape; proanthocyanidins; tannins; fractionation; thiolysis; polydispersity
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