Semisynthetic Preparation and Isolation of Dimeric Procyanidins B1-B8 from Roasted Hazelnut Skins (Corylus avellana L) on a Large Scale Using Countercurrent Chromatography

摘要

Dimeric procyanidins Bl —138 were produced via scmisynthesis from a polymeric proanthocyanidin fraction of hazelnut skins (Corylus avellana L.). This polymeric fraction was found to consist mostly of (+)-catechin and (—)-epicatechin as upper units. Therefore, according to the choice of nucleophile agent, it is possible to semisynthesize dimeric procyanidins Bl, B3, B6, and B7 with (+)-catechin and B2, B4, B5, and B8 with (—)-epicatechin. The semisynthetic mixtures were separated on a preparative scale using high-speed countercurrent chromatography (HSCCC) and low-speed rotary countercurrent chromatography (LSRCCC). C4 → C8 linked dimeric procyanidins Bl—B4 were isolated in amounts of 350—740 mg. To the best of the authors' knowledge this is the first study isolating dimeric procyanidins Bl— B8 in large amounts with countercurrent chromatography. Moreover, the dimeric prodelphinidins Bl, B2, and B3 and their structural elucidation by 'H NMR spectroscopy without derivatization are described for hazelnuts as natural compounds for the first time.