Size-exclusion chromatography of procyanidins: Comparison between apple and grape procyanidins and application to the characterization of fractions of high degrees of polymerization

Apple procyanidins were fractionated on Toyopearl TSK-gel HW-40S or HW-50S resins eluted by an acetone:6 M urea:acetic acid mixture. Determination of number average degrees of polymerization of the procyanidins in eluted fractions confirmed that in those conditions true molecular weight profiles were obtained. This method was applied to polyphenols extracted from cider apples of different varieties at various stages of maturity, from pear juice and from grape seeds. They confirmed existence of very highly polymerized fractions in perry pears and in certain apple varieties. During post-harvest maturation of apples, the number average degree of polymerization of their procyanidins decreased slightly, and their size-exclusion chromatograms showed disappearance of fractions at low Kav values.