Amoxicillin

Keigairengyoto was supplied by Tsumura & Co. (lot number 2140050010, Tokyo, Japan) as a powdered extract obtained by spray-drying a hot water extract mixture of the following seventeen crude drugs: Scutellariae radix, Phellodendri cortex, Coptidis rhizoma, Platycodi radix, Aurantii fructus immaturus, Schizonepetae spica, Bupleuri radix, Gardeniae fructus, Rehmanniae radix, Paeoniae radix, Cnidii rhizoma, Angelicae radix, Menthae herba, Angelicae dahuricae radix, Saposhnikoviae radix, Forsythiae fructus, and Glycyrrhizae radix.
Amoxicillin and clavulanic acid used as reference antimicrobial drugs were purchased from Toronto Research Chemicals (Toronto, ON, Canada). Pure samples of apigenin, baicalein, baicalin, genistein, hesperidin, hesperetin, liquiritin, liquiritigenin, naringenin, glycyrrhizic acid, and glycyrrhetinic acid were purchased from Wako Pure Chemical Industries (Osaka, Japan). apigenin 7-O-glucoside was purchased from Sigma-Aldrich (St. Louis, MO, USA), narirutin from Extrasynthese (Genay, France), and isoliquiritin from Chemfaces (Hubei, China). baicalein, baicalin (baicalein 7-O-glucuronide), luteolin, genistin, wogonin, and wogonoside (wogonin 7-O-glucuronide), and berberine chloride were obtained from Tsumura & Co., with high purities for pharmacokinetic study.

Amoxicillin (87.00%, Batch No. 130409-201913) was obtained from the China National Institute for Food and Drug Control (Beijing, China).
Sulbactam (98.54%, Lot No. DM21022603) was obtained from Guangzhou Juanmu Biotechnology Co., Ltd. (Guangzhou, China).
Amoxicillin diketone piperazine (93.68%, Lot No. DM20051896) was obtained from Guangzhou Juanmu Biotechnology Co., Ltd. (Guangzhou, China). Amoxicilloic acid (99.18%, Lot A634265) was obtained from Toronto Research Chemicals (Wuhan, China).
AS (content detected by HPLC: 93.00%) (Amoxicillin content: 55.50%; sulbactam content: 35.37%). The NMR spectrum of AS is: 1H NMR (600 MHz, DMSO-d6) δ 9.82 (s, 1H, OH), 9.28 (d, J = 7.5 Hz, 1H, NH), 8.57 (s, 1H, NH), 7.28 (d, J = 8.6 Hz, 2H), 6.80 (d, J = 8.6 Hz, 2H), 5.91 (q, J = 6.1 Hz, 2H, OCH2O), 5.59 (t, J = 4.8 Hz, 1H), 5.45 (d, J = 4.1 Hz, 1H), 5.20 (dd, J = 4.6, 1.8 Hz, 1H), 4.95 (s, 1H), 4.56 (s, 1H), 4.42 (s, 1H), 4.03 (q, J = 7.1 Hz, 1H), 3.73–3.65 (m, 1H), 1.49 (s, 3H), 1.46 (s, 3H), 1.36 (s, 3H), 1.35 (s, 3H).
Acetonitrile, methanol, and formic acid were obtained at chromatographic grade from Thermo Fisher Scientific (China) Co., Ltd. (Shanghai, China).