Caffeic acid

ER α, ER β, and buffer recombinant protein were purchased from Shanghai Tongwei Biotechnology Co., Ltd. (China). Ultrafiltration membranes (0.5 ml, 10 kDa) were purchased from Millipore Co., Ltd. (USA).
The MS-grade formic acid and acetonitrile were purchased from Thermo Fisher Scientific Co., Ltd. (USA). The ultra-pure water was obtained from Guangzhou Watsons Food & Beverage Co., Ltd. (China). Dimethyl sulfoxide (DMSO, W387520) was purchased from Sigma-Aldrich Chemical Co. (St. Louis, MO, USA). Other solvents were of analytical grade supplied by Aladdin Industrial Corporation. The chemical reference standards of malic acid, citric acid, caffeic acid, salvianolic acid B, rosmarinic acid, and salvianolic acid C were purchased from Chengdu Pufei De Biotech Co., Ltd. (China). Rutin, isoquercitrin, and quercetin were provided by Cheng Du Herbpurify Co., Ltd. (China). The purities of all the reference standards were above 98% according to HPLC-UV analysis.

Acetonitrile (HPLC grade) was obtained from Fisher Corporation (Waltham, MA, USA). Glacial acetic acid was analytical grade and acquired from Guangzhou Chemical Reagent Factory (Guangzhou, China). Nitric acid 67% was MOS grade and purchased from Tianjin Kemiou Chemical Reagent Co., Ltd. (Tianjin, China). Standards of chlorogenic acid, caffeic acid, vanillin, ferulic acid, senkyunolide I, senkyunolide H, coniferyl ferulate, Z-ligustilide, butylphthalide, senkyunolide A, butylidenephthalide, neocnidilide, and levistilide A (purities ≥ 98% by HPLC) were purchased from Chengdu Pufei De Biotech Co., Ltd. (Chengdu, China). Calibration solutions of 1,000 mg·L⁻¹ of Na, Mg, K, Ca, Mn, Fe, Cu, and Zn were all purchased from Agilent Technologies Inc. (USA). Internal standard elements, consisting of 1,000 mg·L⁻¹ of ⁷³Ge, ¹¹⁵In, and ²⁰⁹Bi, were obtained from National Institute of Metrology (China). All experimental solutions were prepared with ultrapure water (18.2 MΩ·cm⁻¹), which was produced by a purification system (Milli-Q Gradient, Millipore, USA).

Ginsenoside rb1, neocryptotanshinone, caffeic acid and ligustilide (the purities of all standards were higher than 98% by high-performance liquid chromatography analysis) were purchased from Chengdu Pufeide Biotech Co., Ltd. (Chengdu, China).
TRIzol™ Reagent, Fetal bovine serum (FBS), 0.25% Trypsin–EDTA (w/v), Dulbecco’s modified eagle's medium (DMEM), penicillin–streptomycin (10,000 U/mL, P/S), and phosphate-buffered saline (PBS) were purchased from Thermo Fisher Scientific (Waltham, MA, USA). Human MTNR1A polyclonal antibody and GGT1 polyclonal antibody were purchased from CLOUD-CLONE CORP. (CCC, USA). Anti-rabbit IgG, HRP-linked antibody was purchased from Cell Signaling Technology (Danvers, MA, USA). β-actin was purchased from COHESION BIOSCIENCES (SUZHOU, CHINA).