Chem. Pharm. Bull. 53(8) 978—983 (2005)

drug therapeutic and toxic effects. The change of the compatibility of traditional Chinese medicines may lead directly to the change of the metabolism of drug effectiveness in human body. Therefore, the investigation of the metabolism of compound Chinese recipes by modern analytical techniques may play important roles in explanation of the functional mechanisms and compatibility principles of compound Chinese prescriptions. Few studies were performed to investigate the influence of compatibility on metabolism of compound traditional Chinese prescriptions. The compound Shuang-Huang-Lian (SHL) recipe is officially recorded in Pharmacopoeia of China, and has the efficiency of removing toxic heat and inducing diaphoresis. It is commonly used for treating acute upper respiratory tract infection, acute bronchitis and light pneumonia. SHL is composed of three herbs: Flos lonicerae, Radix scutellariae and Fructus forsythiae. Baicalin is the main active ingredient in Radix scutellariae (RS) but does not exist in Flos lonicerae and Fructus forsythiae. There are some investigations on the metabolites of baicalin. For example, in vivo metabolism in rat bile, in human urine after taking baicalin orally and in human plasma after intragastrically (i.g.) taking compound prescription Sho-Kaiko-To, in vitro metabolism by human intestinal flora, this study was designed to compare the metabolites of baicalin in rats after oral administration of SHL and single herb RS, and try to explore the principle of SHL compatibility. Experimental Materials Radix scutellariae (root of Scutellaria baicalesis GEORGI), Flos lonicerae (bud of Lonicera japonica THUNB.) and Fructus forsythiae (fruit of Forsythia suspensa (THUNB.) VAHL.) were purchased from a local herbal shop and were authenticated by Dr. F. Feng (Department of pharmacognosy, China Pharmaceutical University). Baicalin reference (Batch No. 715-200211) was obtained from National Institute for the Control of Pharmaceutical and Biological Products (NICPBP). b-Glucuronidase and sulfatase were purchased from Sigma Co. (U.S.A.). High performance liquid chromatography (HPLC)-grade acetonitrile and methanol, analytical reagent grade phosphoric acid, sodium dihydrogen phosphate, ethyl acetate, sodium hydroxide and glacial acetic acid were used for analysis. Double distilled water was produced in this laboratory. Chromatographic Equipment and Conditions HPLC system (Agilent 1100) was equipped with a G1311A pump, a G1314A programmable diode array detector (DAD) and a G1313A auto-injector. A Hewlett Packard (HP) 1000 computer with in-house developed software was used for on-line data acquisition and subsequent calculations. The analytical column was packed with Lichrospher C18 (Kromasil, 250 mm 4.6 mm ID, 5 mm). The mobile phase was a gradient system with A: methanol : 0.7% acetic acid (35 : 65), B: C2H5OH. The gradient systems of qualitative analysis were A/B 100/0 (0→15 min)→A/B 0/100 (35 min)→A/B 0/100 (45 min). And the detector was set at 274 nm, the flow rate of mobile phase was 1.0 ml/min, and the experiment was performed at room temperature. An Agilent LS ion trap mass spectrometer equipped with an electrospray ionization (ESI) source (San Jose, CA, U.S.A.) was used for mass analysis and detection. The operating parameters of the ion source were optimized to obtain the best performance from the mass spectrometry for the analysis of metabolites. The sensitivity of detection in negative ion mode was found to be much higher than that in positive ion mode. Therefore, instrumental parameters were selected that maximized generation of the molecule ([M H] ) of the test compound, and that also efficiently produced characteristic fragment ions. The MSD parameters consisted of the flow rate of the drying gas (nitrogen) flow, nebulizer (nitrogen) pressure, the drying gas temperature, and the spray voltage, with optimum values of 10 l/min, 35 psi, 350 °C and 3200 V, respectively. 978 Chem. Pharm. Bull. 53(8) 978—983 (2005) Vol. 53, No. 8