Quercetin standard

The flowers of E. gardneri were purchased from ZangXiTang Co., Ltd (Tibet, People’s Republic of China). Quercetin standard, rutin standard and isoQuercetin standard were purchased from Solarbio (Beijing, People’s Republic of China). MIN-6 cell line was purchased from Cell Bank of Chinese Academy Sciences (Beijing, People’s Republic of China). Both RPMI-1640 medium and fetal bovine serum were purchased from Gibco (Gaithersburg, MD, USA). Glimepiride, AZD8330 (inhibitor of ERK1/2), nifedipine (inhibitor of Ca²⁺ channel) and fluo-3 AM were obtained from Sigma-Aldrich (St Louis, MO, USA). Thiazolyl blue tetrazolium bromide (MTT) was purchased Merck (Darmstadt, German). Insulin concentrations in cell supernatant were determined using the Mouse Insulin Elisa Kit obtained from Crystal Chem (Downers Grove, IL, USA). Rabbit anti-ERK1/2 antibody, rabbit anti-phospho-ERK1/2 antibody (Thr202/Tyr204) and apoptosis-related antibody were purchased from Cell Signaling Technology (Danvers, MA, USA). Annexin V-FITC/PI Apoptosis Detection Kit was purchased from Merck. MitoProbe JC-1 Assay Kit was a product from Thermo Fisher Scientific (Waltham, MA, USA). Triglyceride Quantification Assay Kit (Colorimetric/Fluorometric) and Glycogen Colorimetric/fluorometric Assay Kit were obtained from Abcam (Cambridge, UK).