Reversed-phase liquid chromatographic analysis of hydrophobic interaction between proanthocyanidins and a C8-alkyl compound in aqueous solution |
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Authors: | Akio Yanagida Shinya Takeshige Yoichi Shibusawa |
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Affiliation: | Division of Pharmaceutical and Biomedical Analysis, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Japan |
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Abstract: | Structural and physicochemical properties of oligomeric flavan-3-ols (proanthocyanidins) in aqueous solution were investigated by spectrometric and reversed-phase (RP) HPLC analyses. Circular dichroism and fluorescence spectra of (–)-epicatechin (EC) oligomers linked through C-4 to C-8 interflavan bonds showed that EC oligomers larger than dimers formed a stable secondary structure in water. These EC oligomers are water-soluble hydrophilic compounds, whereas the oligomers were strongly retained by a C8-alkyl stationary phase under conventional RP-HPLC conditions. In a further C8-HPLC study, the hydrophobic interaction between EC oligomers and 1-octanesulfonic acid sodium salt (OSA Na) added to the mobile phase was quantitatively evaluated based on the relationship between the logarithm of the retention factor of the solute and the OSA Na concentration in the mobile phase. The strength values of the hydrophobic interaction of EC oligomers larger than dimers were the highest of 22 tested polyphenolic standards. |
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Keywords: | proanthocyanidins circular dichroism reversed-phase liquid chromatography hydrophobic interaction 1-octanesulfonic acid |
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