Chemicals and reagents

CA, PG, PA, and Taxol were purchased from Chengdu DeSiTe Biological Technology Co. Ltd. (Chengdu, China). The purities of all compounds were determined by HPLC (≥98%). Their chemical structures are presented in Figure 1. HPLC-grade acetonitrile and methanol were purchased from Thermo Fisher Scientific (Waltham, MA, USA). HPLC-grade formic acid was obtained from Shanghai Aladdin Biochemical Technology Co. Ltd. (Shanghai, China). Water for HPLC–MS/MS analysis was purified using a Direct-Q 5UV ultra-pure water purification system (MilliporeSigma, Burlington, MA, USA).

Chemical structures of the analytes and internal standard (Taxol).

Astragali Radix (the dried root of Astragalus membranaceus (Fisch.) Bge.var. mongholicus (Bge.) Hsiao), Paeoniae Radix Rubra (the dried root of Paeonia lactiflora Pall.), and Saposhnikoviae Radix (the dried root of Saposhnikovia divaricata (Turcz.) Schischk.) were purchased from a local pharmacy in Beijing, China and authenticated by Prof. Chunsheng Liu from Beijing University of Chinese Medicine. The voucher specimens were kept in our laboratory.