Pharmacokinetics Of The Madecassoside In SD Rats

Objective: To investigate the pharmacokinetics of MD (madecassoside) in SD rats and obtain the main pharmacokinetics parameters, tissue distribution and excretion by HPLC (High Performance Liquid Chromatography) methods to establish for determination of MD in rat plasma, tissue, urine, feces and bile.Methods:(1)After single iv injection dose of 14, 42 or 126 mg/kg MD in SD rats, the rats were sacrificed at 1, 3, 5, 10, 20, 30, 60 and 120 min and the plasma and tissues were obtained to detect. Meanwhile, the urine, feces, bile of rats were collected to dectect.(2)Methanol (containing the internal standard cucurbitacin B 10μg) was added in plasma and other samples. After centrifuging of mixed solution and purifying of supernatant with the solid phase extraction column, the eluent was determined by HPLC.(3)HPLC conditions: Welchrom-C18 column(250 mm×4.6 mm,5μm), water-acetonitrile (24∶76) as mobile phase (flow rate: 1.0 mL/min), cucurbitacin B as internal standard, detection wavelength: 225 nm, column temperature: 30℃.Results:(1) In this HPLC conditions, the retention time of the MD and the cucurbitacin B was respectively 5.11 min and 8.14 min. The low limit of detection was 1μg/mL.The recoveries were 80.65%～103.7%. The within-day RSD (Relative Standard Deviation) and between-day RSD were between 0.54%～3.62%(n=5).(2) The pharmacokinetic model of MD fitted well with the two-compartment open model after a single MD iv dose of 14, 42 or 126 mg/kg in SD rats. The main parameters of three groups were as follows: T1/2αwere 2.40,1.96 and 1.95 min,T1/2βwere 25.62,23.12 and 25.13 min,Vc (Central compartment apparent volume of distribution) were 0.01,0.02 and 0.03 mL/mg,CL (Clearance) were 0.0009,0.0013 and 0.0021 mL/min/mg,AUC (Area Under Curve) were 16000.89,32864.89 and 61200.52μg·min/mL,MRT (Mean Residence Time) were 36.98,33.37 and 36.26 min, respectively.(3) MD was widely distributed to virtually all tissues quickly. It was mainly distributed in liver, kidney, and spleen. The concentration of MD in tissues attaineded to the highest levels at 20 min and decreased significantly at 120 min after administrating.(4) The excretion of MD in urine, feces and bile amounted to 82.86%, 6.98% and 1.53% of the dose, respectively. The parent drug excretion amounted to 78.5% of the dose in 2 h.Conclusions: The SPE-HPLC (Solid-Phase Extraction High Performance Liquid Chromatography) is a suitable method for study the pharmacokinetics of MD in SD rats. The pharmacokinetic model of MD comforms as the two-compartment open model and first order kinetics in SD rats. The pharmacokinetics of MD after iv administration demonstrats a rapid distribution and elimination process in SD rats. The parent drug excretion is mainly via urine.