Chromatographic separation of phenolic compounds from rapeseed by a Sephadex LH-20 column with ethanol as the mobile phase

Phenolic compounds from rapeseed were chromatographed using an open column filled with Sephadex LH-20 as the stationary phase and ethanol as the mobile phase. Typically, methanol has been used as the eluent of choice in previous studies, but it was hypothesized that ethanol's lesser polarity would provide better separation of the rapeseed phenolics. In this work, three fractions (I-III) containing phenolic compounds were collected; their characteristics were evaluated qualitatively and quantitatively by UV spectrophotometty, a colorimetric assay, and capillary electrophoresis (CE). Although fraction I possessed the greatest relative proportion of the crude extract (62.2%), fraction III contained the richest source of rapeseed phenolics (176 mg transsinapic acid equivalents g(-1)). Capillary electrophoresis identified sinapine as the dominant phenolic compound of fraction I and indicated that a number of phenolic compounds were present in fractions 11 and III. Although free and esterified derivatives of phenolic acids were constituents of fraction II, the electropherogram revealed that sinapic acid was the chief phenolic compound present, based on retention time mapping. Application of ethanol as the eluent, rather than methanol, gave a better baseline separation of the phenolic constituents from rapeseed.