*3.3. UPLC-MS*/*MS Analysis*

UPLC-MS/MS analyses were performed using a linear ion trap-orbitrap mass spectrometer (Orbitrap Elite; Thermo Fisher Scientific, Bremen, Germany) coupled with the online UPLC system (ACQUITY UPLC; Waters, Waters Corp., Manchester UK). The working solution was separated by an ACQUITY UPLC BEH C18 column (100 × 2.1 mm, 1.7 μm; Waters) at 40 ◦C. The flow rate of mobile phase A (ddH2O) and B (methanol) was 0.3 mL/min. The sample injected 5 μL. The gradient program was set as 20–30% phase B from 0–1 min and 30–100% phase B from 1–25 min. The column was washed with 100% phase B for 5 min before being re-equilibrated for 5 min. The mass spectrometer was equipped with an electrospray interface controlled by the Xcalibur software (version 2.0, Thermo Fisher Scientific, Bremen, Germany) with two types of operations: The positive ion and negative ion modes. The ESI source was set at these parameters: Spray voltage of 3.5 kV for the positive-ion mode and −3.2 kV for the negative-ion mode; capillary temperature was set at 360 ◦C and the source heater temperature was maintained at 350 ◦C. During the analysis, the mass spectrometer performed high-resolution (resolving power, r = 15,000) full scan cycles (*m*/*z* 100–1000). The analyte profiles were first made by the orbitrap; the MS2 spectra were then recorded in the centroid mode for the five most intense ions. The isolation width was set at the mass-to-charge ratio (*m*/*z*) of 0.2 and the higher-energy collisional dissociation (HCD) was performed at collision energies of 20, 30, 40 and 50 eV
