Leucine enkephalin le

The CCS value and DIA analysis (MS^E) were performed on a traveling wave ion-mobility hybrid quadrupole time-of-flight mass spectrometer with an ESI ion source (SYNAPT G2-Si, Waters, Wilmslow, UK) in resolution mode (~30,000 FWHM at m/z 500). The MS data were acquired from 100 to 1500 Da in positive and negative ion modes. The ESI source parameters were set as follows: capillary voltages of 0.5 kV (ESI+) or 2.5 kV (ESI−), a cone voltage of 40 V, a source offset of 60 V, a source temperature of 120 °C, desolvation gas flow of 800 L/h, desolvation gas temperature of 500 °C, and a cone gas (N₂) flow of 20 L/h. The traveling wave ion-mobility mass separation parameters were set as follows: helium cell 95 mL/min; triWave, IMS wave velocity 650 m/s, wave height 20 V, transfer wave velocity 176 m/s; IMS wave velocity ramp starting at 80 m/s and ending at 1000 m/s. The MS and MS^E data scanning time was set at 0.5 s. Leucine enkephalin (LE; Sigma-Aldrich, St. Louis, MO, USA; 200 ng/mL) and sodium formate solvent (0.5 mmol/L) were used as the calibration standards. The CCS accuracy was calibrated with poly-dl-alanine solution (10 mg/L). MassLynx V4.1 software (Waters, Milford, MA, USA) was employed for data acquisition and processing.

Acetonitrile, methanol (Merck, Darmstadt, Germany), leucine-enkephalin (LE, Sigma-Aldrich, St. Louis, MO, USA, No. L9133-50MG), formic acid (FA; CNW, Shanghai, China), and ammonium formate (AF; Sigma-Aldrich, MO, USA, No. 41470) were of HPLC grade. Deionized water was purchased from Guangzhou Watson’s Food & Beverage Co., Ltd. (Guangzhou, China). A total of five species of the officinal PSA herb genus Panax, including Panax ginseng, P. quinquefolius, P. japonicus, P. japonicus var. major, and P. notoginseng, were collected from wild or cultivated sources in China and the United States in 2018 (Figure 7).

High performance liquid chromatography (HPLC) grade methanol and acetonitrile were obtained from Merck (Darmstadt, Germany). Analytical grade formic acid and HPLC grade ammonium acetate were purchased from ROE Scientific inc (Newark, DE, USA). Leucine enkephalin (LE) was purchased from Sigma-Aldrich (St. Louis, MO, USA). L-2-chlorophenylalanine and standards for metabolite identification were bought from Shanghai Aladdin Bio-Chem Technology Co., LTD. A Milli-Q purification system (Bedford, MA, USA) was used to provide ultra-pure water. A total of 2.0-mL vials were purchased from Agilent (Palo Alto, CA, USA).