Epi catechin

Methanol, chloroform, dichloromethane, ethyl acetate, formic acid, and n-hexane were purchased from POCh (Gliwice, Poland). Acetonitrile was purchased from Merck (Darmstadt, Germany). Water for HPLC experiments was prepared using the Milli-Q Plus system (Millipore, Billerica, MA, USA) (18.2 MΩ cm). All solvents used for chromatography were of gradient grade. Cyclolariciresinol, 7-hydroxylariciresinol (I), 7-hydroxylariciresinol (II), 7-hydroxymatairesinol, lariciresinol, matairesinol, nortrachelogenin, pinoresinol, secoisolariciresinol, and todolactol were isolated in our laboratory. Myricetin, dihydroquercetin (taxifolin), and epi-catechin were purchased from Serva (Heidelberg, Germany). Abietic acid and catechin were purchased from Sigma-Aldrich Chemie GmbH (Steinheim, Germany).

This analysis was performed using an Agilent 1200 HPLC system, which included a Zorbax SB-C18 column (5 mm, 4.6 × 150 mm) and was equipped with a diode array detector and a ChemStation system for collection and processing of chromatographic data (Agilent Technology, Santa Clara, CA, USA). The separation was conducted under the following conditions: in the mobile phase, the concentration of methanol in the solution of phosphoric acid (0.1%) was changed from 22% to 100% during 36 min. The eluent flow rate was 1 mL/min, column temperature was 26 °C, and sample volume was 10 µL; the detection was conducted at wavelengths 254, 210, 230, 280, 315, 340, and 360 nm. Quantification of individual compounds in the plant extract samples was conducted by the external standard method. For detection of catechins in the plant extract, standard samples of (±)-catechin (Sigma-Aldrich, Taufkirchen, Germany Germany), (−)-epicatechin (Serva, Heidelberg, Germany), and epigallocatechin gallate (Teavigo, Kaiseraugst, Switzerland) were employed, from which standard solutions were prepared (10 μg/mL).