A high-performance gel permeation chromatography fluorescence detection (HPGPC-FD) method combined with fluorescein isothiocyanate (FITC) labeling was established for the microanalysis of L. barbarum polysaccharides (LBP). The calibration curves linear over the range of 0.2-20 µg/mL in rat plasma, and 0.25-500 μg/mL in urine and feces samples with correlation coefficients greater than 0.99. The inter-day and intra-day precisions (RSD, %) of the method were under 15% with the relative recovery ranging from 84.6% to 104.0% and the RSD ranging from 0.47% to 7.28%. The concentration-time curve of LBP-FITC in plasma following intragastric administration at 100, 50 and 25 mg/kg well fitted to a nonlinear model. LBP-FITC slowly eliminated from plasma according to the long half-lives (t1/2 = 31.39, 38.09, and 45.76 h, respectively) and mean retention times (MRT0-t = 18.38, 19.15 and 20.07 h, respectively; AUC0-∞ = 230.49, 236.18 and 242.57 h, respectively) after administration of LBP-FITC at doses of 100, 50, and 25 mg/kg, respectively. After intragastric administration at 50 mg/kg for 72 h, the concentration of LBP-FITC in urine and feces was 0.09 ± 0.04% and 92.18 ± 3.61% respectively; the excretion rate of urine was the highest in 0-4 h period and decreased continuously in 4-24 h period. The excretion rate of feces was the highest in 4-10 h, 48.28 ± 9.349% in feces within 4-10 h, and decreased rapidly in 10-24 h. The present study showed that LBP was absorbed as its prototype and most proportion of LBP was excreted from feces, indicating a long time remaining in intestine.
Keywords: L. barbarum polysaccharides; excretion; fluorescein isothiocyanate; pharmacokinetic.