Tetramethylsilane

GLJ (batch No.: 20170726) was generously provided by Shanxi Guangyuyuan Traditional Chinese Medicine Co., Ltd. (Jinzhong, China). Standard references included kaempferol (≥98%, batch No.: MUST-17032911), psoralen (≥98%, batch No.: MUST-16092810), baohuoside Ⅰ (≥98%, batch No.: MUST-19042203), isobavachalcone (≥98%, batch No.: MUST-16102615), neobavaisoflavone (≥98%, batch No.: MUST-16092810), bavachinin A (≥98%, batch No.: MUST-18101705), oleanolic acid (≥98%, batch No.: MUST-17042706), ginsenoside Re (≥98%, batch No.: 180829), and ginsenoside Rg1 (≥98%, batch No.: 180917), which were obtained from Chengdu Must Biotechnology Co., Ltd. (Chengdu, China) and Shanghai Ronghe Pharmaceutical Technology Development Co., Ltd. (Shanghai, China). Methanol, petroleum ether, ethyl acetate, and n-butanol of analytical grade were purchased from Tianjin Four Fine Chemicals Co., Ltd. (Tianjin, China). Ultrapure water was prepared with a Milli-Q water purification system (Millipore, Bedford, MA, USA). Methanol of LC-MS grade and formic acid of HPLC grade were obtained from Thermo Fisher Scientific Inc. (Thermo Fisher Scientific, Waltham, MA, USA). Deuterated chloroform (CDCl₃, 99.8% D) containing tetramethylsilane (TMS, 0.03%, m/V) and methanol-d₄ (99.8% D) were obtained from J&K Scientific Ltd. (Beijing, China).

Choline hydroxide (45 wt% in H₂O) was purchased from Sigma-Aldrich, St. Louis, MO, USA. Amino acids and tetramethylsilane were obtained from J&K Scientific Ltd., Beijing, China. Details on the preparation and characterization of [Chl][AA] ILs are provided in ESI Fig. S1.† [OPy][Br] IL was purchased from the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, China. The maize seeds (Zhengdan958, Zea mays L.) used in this study were purchased from Doneed Seeds Ltd., Beijing, China.