Novel separation of bioactive catechin derivatives from complex plant mixtures by anion-exchange chromatography

The paper presents the use of anion-exchange chromatography to separate bioactive cysteine containing catechin conjugates from underivatised polyphenols and oligomeric material. The conjugates were excluded from the anion-exchange resin using a low percentage of organic solvent, enough to eliminate the weak hydrophobic interactions with the matrix. The rest of the uncharged polyphenols were unexpectedly retained by the matrix and eluted by the addition of salt. Cation–π interactions between the quaternary amino group on the resin and the electron-rich faces of the flavanol's aromatic rings might be responsible for this unexpected behaviour. Because immobilized anions retain uncharged polyphenolic material, anion-exchange chromatography may be a convenient approach to separate polyphenols from other bioactive compounds in complex mixtures of plant origin.