Platycodin d

The reference standards of isorhmnetin (3), diosmetin (6), isochlorogenic acid A (7), kaempferol (10), quercetin (14), isochlorogenic acid C (15), apigenin (19), forsythin (20), chlorogenic acid (23), liquiritin (25), luteolin-7-O-glucoside (26), astragalin (28), luteolin (29), buddleoside (31), quercetin-3-O-glucoside (33), amygdalin (37), caffeic acid (38), forsythoside A (39), glycyrrhizic acid (40), ferulic acid (42), rutin (44), hyperoside (50), and platycodin D (51) were purchased from Sichuan Weikeqi Biological Technology, Co., Ltd. (Chengdu, China). Mulberry leaf, chrysanthemum, Fructus Forsythiae, licorice, Semen Armeniacae Amarum, Platycodi Radix and Phragmitis Rhizoma were purchased from Guangdong Huiqun Chinese Traditional Medicine, Co., Ltd. (Shantou, China), and mint was provided by Jiangxi Jianmin Natural Perfume Factory (Ji’an, China). Their voucher specimens have been deposited at the Department of Pharmaceutical Analysis, Xuzhou Medical University, Xuzhou, China. All other reagents were of analytical grade and obtained commercially.

The reference compounds syringin, lobetyolin, platycodin D, platycodin D₂, deapio-platycodin D were from Sichuan Wei Keqi Biological Technology Co., Ltd. (Sichuan, China). Sulfur, complied with the Chinese Pharmacopoeia (2010 edition), was obtained from the Chinese Medicine Clinic of Hong Kong Baptist University.
Stock standard solutions of syringin, lobetyolin, platycodin D, platycodin D₂, deapio–platycodin D (each about 1 mg/mL) were separately prepared in methanol and were stored at 4 °C before use. A mixed reference standard solution was prepared by mixing and diluting the five stock standard solutions with methanol to get a concentration of 0.1 mg/mL for each standard. The solution was filtered through a 0.45 μm PTFE filter prior to UHPLC UHD Q-TOF MS/MS analysis.