2.6. Separation of Polymethoxyflavones by Prep-HPLC

The separation was based on our previous study and performed on a XBridge C18 column (19 × 250 mm, 5 μm) with the conditions as follows: acetonitrile-water (A) with 0.1% formic acid (B) was used as the mobile phase with a gradient elution (0–6 min, 18–30% A; 6–35 min, 30–42% A; 35–45 min, 42–60% A; 45–50 min, 60–18% A), the flow rate was 20 mL/min, and the injection volume was 650 μL. Peak fractions were collected automatically according to the retention time and the online-QDa detection. Each peak from the chromatogram was collected, evaporated under reduced pressure, and then analyzed by UPLC-Q-TOF-MS/MS and NMR as reported [19].