Separating four diastereomeric pairs of dihydroflavonol glycosides from Engelhardia roxburghiana using high performance counter-current chromatography

Four pairs of diastereomers were successfully isolated and separated from the water extract of Engelhardia roxburghiana by high performance counter-current chromatography (HPCCC) using a two-step procedure. The diastereomers were initially separated by a two-phase solvent system composed of n -hexane– n -butanol–0.1% trifluoroacetic acid (1:2:3, v/v/v) and followed by the same solvent system using hydroxypropyl-β-cyclodextrin (HP-β-CD) as an additive. The chromatographic conditions, elution mode, and concentrations of the additive were refined. The two-step HPCCC isolation yielded 43.7   mg (2S, 3S)-astilbin, 27.6   mg (2R, 3R)-astilbin, 5.9   mg (2S, 3R)-astilbin, 4.8   mg (2R, 3S)-astilbin, 6.9   mg (2S, 3S)-engelitin, 3.1   mg (2R, 3R)-engelitin, 8.2   mg (2S, 3R)-engelitin, and 6.0   mg (2R, 3S)-engelitin from 384   mg crude extract in four runs with purities of 99.3%, 96.2%, 99.8%, 99.9%, 97.0%, 96.5%, 96.1%, and 96.8%, respectively. The present study revealed that HP-β-CD can be used as an additive in HPCCC to effectively improve the resolution of the diastereomers. The established HPCCC method may serve as an approach to obtain high purity diastereomers on a large scale.