Quinidine

VB₁₂ standard was purchased from Sigma Chemical Co. (St. Louis, MO, USA). Quinidine and cyclosporin A were obtained from Macklin Biochemical Co., Ltd. (Shanghai, China). Verapamil was from Heowns Biochemical Technology Co., Ltd. (Tianjin, China). Fluorescein sodium standard was purchased from National Institute for the Control of Pharmaceutical and Biological Products (NICPBP, China). Labrasol and G44/14 were generous gifts from Gattefossé (Saint-Priest, France). Kreb’s Ringer Buffer (KRB) was purchased from Yuanye Biochemical Technology Co., Ltd. (Shanghai, China). Caco-2 cells were obtained from Key GENBioTECH Corp., Ltd. (Nanjing, China). Dulbecco’s Modified Eagle’s Medium (DMEM), were obtained from Gibco™ (Grand Island, NY, USA). Fetal bovine serum (FBS) was purchased from Ex Cell Biology, Inc. (Shanghai, China). MTT was from Sangon Biotech Co., Ltd. (Shanghai, China). Hank’s balanced salt solution (HBSS), phosphate buffer saline (PBS) powder, trypsin, penicillin–streptomycin solution (100X) and dimethyl sulfoxide (DMSO, cell culture grade) were obtained from Solarbio Science & Technology Co., Ltd. (Beijing, China). Transwell® Permeable Supports were from Costar® (Corning Inc., USA). The solvents were of the High Performance Liquid Chromatography (HPLC) grade. Other reagents were of the Analytical Reagent (AR) grade.

Liquid chromatography-mass spectrometry (LC-MS) grade acetonitrile (ACN) and methanol (MeOH) were purchased from Thermo Fisher Scientific (Waltham, MA, USA). Formic acid (FA) was purchased from Merck (Darmstadt, Hessen, Germany). Purified water was obtained from Wahaha (Hangzhou, China). The drug standards paclitaxel (PTX), docetaxel (DTX), and methyl-D9-choline chloride were purchased from Zhenzhun Biotechnologies Co., Ltd. (Shanghai, China). The four modified taxane compounds were provided by BioDuro Shanghai Co., Ltd. (Shanghai, China). PTX injection was obtained from Yangtze River Pharmaceutical Co., Ltd. (Taizhou, China). Hemicholinium-3 (HC-3) was obtained from Sigma-Aldrich (Shanghai) Trading Co., Ltd. (Shanghai, China). Quinidine and cimetidine were purchased from Macklin (Shanghai, China) and Solarbio (Beijing, China), respectively. Bis(p-nitrophenyl) phosphate (BNPP) was obtained from Shanghai yuanye Bio-Technology Co., Ltd (Shanghai, China). Huperzine A and neostigmine bromide were purchased from J&K Scientific Ltd (Beijing, China).