Preparative isolation of apple Flavan-3-ols by pH-zone-refining centrifugal partition chromatography combined with reversed-phase liquid chromatography
Résumé
Condensed Tannins are of great interest in organoleptic properties of apple-based beverages, particularly due to their oxidation caused by technologic processes. To better understand the impact of oxidation of procyanidins on astringency sense and quantify oxidation products, it was necessary to isolate tannins from raw materials, for model-solution studies. A gentle strategy combining pH-zone-refining centrifugal partition chromatography (pH-ZRCPC) and preparative reversed-phase liquid chromatography (Prep-RPLC) was developed to recover the main phenolic compounds families separately, from 1 g apple crude extract. First, a pH-ZRCPC fractionation was optimized to remove hydroxycinnamic acids, with a biphasic mixture composed of ethyl acetate-n-butanol-water (3:2:5) in descending mode. Trifluoroacetic acid (10 mM) and sodium hydroxide (10 mM) were used as retainer and eluter, in the upper and lower phases, respectively. Secondly, easy Prep-RPLC separation was carried out in isocratic mode at 20% ACN to discard dihydrochalcones. Finally, 409 mg of a highly purified tannin extract with a mean degree of polymerisation of 5.5 was obtained with a recovery of 100%.
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