Fractionation of Procyanidins from Granny Smith Apples According to Degree of Polymerization and Preparation of Pure Procyanidin Oligomers

Procyanidins are a class of condensed tannins widely present in natural plants with various bio-activities, which are closely related to their degree of polymerization. The preparation of oligomeric procyanidins from Granny Smith apple, which are believed to contain ample procyanidins, will facilitate the study of procyanidins structures and bio-activities. Procyanidins in Granny Smith apples were extracted with water, purified by ADS-17 macroporous resin and fractionated by TSK HW-40s resin and 9 fractions were obtained. High performance liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) analysis indicated that these fractions were composed of quercetin and phloridzin, catechin and epicatechin, and dimers, trimers, tetramers and pentamers in. Procyanidins B2 (epicatechin-(4β-8)-epicatechin) and C1 (epicatechin-(4β-8)-epicatechin-(4β-8)-epicatechin) with relatively high purity were prepared by slective collection of fractions, and were further identified by circular dichroism (CD) and nuclear magnetic resonance (NMR).