Chemstation system

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).

Quantification of flavonoids in the leaf samples was performed by means of an Agilent 1200 HPLC system equipped with a diode array detector and a ChemStation system for recording and processing chromatographic data (Agilent Technologies). The chromatographic separation was carried out on a Zorbax SB-C18 column (5 μm, 4.6 × 150 mm) at 25 °C. Methanol concentration in the mobile phase in an aqueous solution of phosphoric acid (0.1%) was increased from 50% to 52% for 56 min [35 (link)], and the eluent flow rate was 1 mL/min. Detection wavelengths were 254, 270, 290, 340, 360, and 370 nm. Individual compounds were quantified by an external standard method [29 (link)]. Mean values are expressed in milligrams per gram of air-dried matter.