Reversed-phase liquid chromatographic analysis of hydrophobic interaction between proanthocyanidins and a C₈-alkyl compound in aqueous solution

Figures & data

Fig. 1. Structures of monomeric and oligomeric flavan-3-ols used as experimental standards.

Fig. 2. CD, UV, and FL (emission spectra excited at 281 nm) spectra of EC (1c) and EC oligomers (2b, 3a, 4a, 5a) in water.

Note: The concentration of each sample was 50 μg/mL for CD and UV analyses, and 1 μg/mL for FL analysis.

Fig. 3. Merged chromatogram of eleven flavan-3-ol standards separated by RP C₈-HPLC in isocratic elution mode.

Notes: Column: Chromolith Performance RP-8e (4.6 mm I.D. × 100 mm; Merck); mobile phase: acetonitrile–aqueous 0.1% TFA (10:90, v/v); flow rate: 2.0 mL/min; detection: absorbance at 280 nm; injection volume: 10 μL; concentration of each standard: 50 μg/mL. The number of each peak corresponds to the number of each standard shown in Fig. 1.

Fig. 4. Relationship between log k values of eleven standards in C₈-HPLC and their log P_o/w values.

Notes: The inset regression equation (A) was obtained from six monomeric flavan-3-ols (1a–1f). The regression equation (B) was for EC (1c) with respect to four EC oligomers (2b, 3a, 4a, 5a) linked with (4β→8) bond

Fig. 5. Comparison of C₈-HPLC profiles of EC oligomers and related flavan-3-ol standards in different mobile phases.

Notes: A: acetonitrile–aqueous 0.1% TFA (10:90, v/v); B: solvent A containing 10 mM OSA·Na. Other chromatographic conditions were identical to those described in Fig. 3 caption.

Fig. 6. Relationship between the concentration of OSA·Na added to mobile phase (solvent A) and log k values of seven standards in C₈-HPLC in each mobile phase.

Fig. 7. Comparison of S values of twenty-two polyphenolic standards.