Isoliquiritigenin

Acetonitrile, methanol, and formic acid were HPLC grade and provided by Merck (Darmstadt, Germany). Reference standards, including hypaphorine, isoliquiritigenin, naringin, formononetin, and maackiain, were of high purity grade (purity > 98%) and purchased from Chengdu Must Biotechnology Co., Ltd. (Chengdu, China). The 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) were provided by Sigma-Aldrich (St. Louis, MO, USA). Pure water was provided by Wahaha (Hangzhou, China). The kits of lactic dehydrogenase (LDH), Ca²⁺-Mg²⁺-ATPase (ATPase), superoxide dismutase (SOD), and malondialdehyde (MDA) were provided by Nanjing Jiancheng Biological Engineering Research Institute.

High-performance liquid chromatography (HPLC) grade acetonitrile, methanol, and formic acid were obtained from Sigma-Aldrich (St. Louis, MO, USA). Ultrapure water was prepared using a Milli-Q water system (Millipore, Billerica, MA, USA). Chemical references, including liquiritin, liquirtigenin, isoliquiritin, isoliquiritigenin, and glycyrrhizin, were purchased from Chengdu Must Bio-Technology Co., Ltd. (Chengdu, China). Isoforsythiaside A, forsythoside A, and forsythin were obtained from Shanghai YuanYe Biotechnology Co., Ltd. (Shanghai, China). Chlorogenic acid, forsythoside B, and obacunone were obtained from the National Institutes for Food and Drug Control (Beijing, China). All standards were determined to have a purity of ≥95% by HPLC. All references were deliquated with methanol to a concentration of 50.0 μg/mL. PTQX granules were produced on a pilot-scale by Jiangyin Tian Jiang Pharmaceutical Co., Ltd. (Jiangsu, China).
DNCB (1-chloro-2,4-dinitrobenzene) and enzyme-linked immunosorbent assay (ELISA) kits for IgE were obtained from Sigma-Aldrich. Mouse Th1/Th2/Th17 and Th17/Treg phenotyping kits were obtained from BD Biosciences (San Jose, CA, USA). All other chemicals and solvents were of the highest commercially available grade.