2.3. High-performance liquid chromatography (HPLC) analysis
Shimadzu SCL-10AVP was used for HPLC analysis equipped with the column Inertsil ODS-3.5 μm (4.6 × 250 mm). Samples of 20 μL were injected into the column and eluted with a gradient comprising for the mobile phase acetonitrile (Pump A) and 0.1% glacial acetic acid/water (Pump B) were used. The 6 phenolic acids analysed in this study were p-coumaric, o-coumaric, caffeic, ferulic, sinapic and gallic acids (Sigma, USA). The following gradient was at 86% B at 0–10 min, 74% B after 32 min, 20% B for 35–38 min, and 86% B for 40–43 min. Flow rate was 1 mL/min, and column temperature was 40 °C. Detection was performed by scanning from 200 to 540 nm and the quantitative analysis was done at 280 nm.