Fractionation of apple procyanidins according to their degree of polymerization by normal-phase high-performance liquid chromatography

A new method was developed for the fractionation of procyanidin oligomers according to their degree of polymerization. Monomeric flavan-3-ols and low molecular mass procyanidins were selectively extracted from the lyophilized powder of apple condensed tannins (ACTs) by methyl acetate extraction. Sequentially, the separation of each oligomer from dimer to pentamer in this extract was carried out by normal-phase high-performance liquid chromatography using a silica-beads packed column. The best separation was achieved with a mobile phase system containing hexane; (1) hexane–methanol–ethyl acetate, (2) hexane–acetone. These sequential treatments can be easily adapted to large-scale fractionation.