Fig. 3.

  a  HPLC chromatogram of the standard solution with approximately 100 µg procyanidin B2/mL after hydrolysis, detected at 530 nm. b  HPLC chromatogram of the standard solution with approximately 10 µg procyanidin B2/mL after hydrolysis, detected at 530 nm. c  HPLC chromatogram of one sample solution after hydrolysis, detected at 530 nm. The retention times differ from the method used for molecular characterization ( Fig. 2 ). The integrals of the measured peaks are within the range of the calibration.