Methyl gallate

Methanol (HPLC grade and MS grade) was purchased from Fisher Scientific (Waltham, MA, USA). Distilled water was purchased from Watson's Food & Beverage Co., Ltd. (Guangzhou, China). Acetic acid (MS grade) was purchased from Fisher Scientific (Waltham, MA, USA). Reference standards of gallic acid (98%, CAS No: 149-91-7), punicalagin A (63%, CAS No: 65995-63-3), punicalagin B (37%, CAS No: 65995-63-3), methyl gallate (98%, CAS No: 99-24-1), geraniin (98%, CAS No: 2360976-49-0), corilagin (98%, CAS No: 23094-69-1), chebulinic acid (98%, CAS No: 18942-26-2), chebulagic acid (98%, CAS No: 23049-71-5), and ellagic acid (98%, CAS No: 476-66-4) were purchased from Chengdu-PUSH Bio-Technology Co., Ltd. (Chengdu, Sichuan, China).

The standard compounds paeoniflorin, albiflorin, catechin, lactiflorin, benzoylpaeoniflorin, 1,2,3,4,6-O-pentagalloylglucose, ethyl gallate, 3,4-dihydroxybenzaldehyde and 3,4-dihydroxybenzoic acid were purchased from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China). Gallic acid, oxypaeoniflorin, methyl gallate, benzoic acid, and apiopaeonoside were obtained from Chengdu Push Bio-Technology Co., Ltd. (Chengdu, China). The purity of each standard was >98%. The chemical structures of the 14 reference compounds were presented in Supplementary Figure 1. A Milli-Q system (Millipore, MA, United States) was used to prepare ultra-pure water. HPLC-grade acetonitrile and methanol were procured from Tedia (Fairfield, OH, United States), and formic acid (LC-MS grade) was purchased from Aladdin (California, United States). All other reagents were of analytical grade.