Abstract: This study investigated serum absorption, tissue distribution, and excretion characteristics of purified Lycium barbarum polysaccharides (LBP) in mice following oral administration using a fluorescent labeling method. The results showed that LBP were successfully labeled with fluorescein isothiocyanate (FITC) and sulfo-cyanine 7 (Cy7). In vivo imaging revealed strong fluorescence intensity in the small intestine and liver after oral administration of LBP-Cy7. The small intestine exhibited peak fluorescence intensity at 1 h, while the liver showed peak intensity at 6 h, indicating that polysaccharides absorbed in the small intestine primarily accumulate in the liver. The LBP-FITC assay was validated for its excellent precision (intra-day and inter-day relative standard deviation (RSD) < 15%), stability RSD < 15%, and recovery rates (97.2%–100.8%) in serum, tissues, feces, and urine. Following a single oral gavage of 50 mg/mL LBP-FITC in mice, its peak serum concentrations were detected at 2 h, with a long elimination half-life (t1/2) of (8.67 ± 1.23) h. Tissue distribution analysis indicated that LBP-FITC primarily distributed in the stomach, small intestine, large intestine, and liver after oral administration. The decreasing order of tissue distribution was small intestine > stomach > large intestine > liver > kidney > lung > heart > spleen, with maximum accumulation in the liver occurring at 6 h. Within 48 h post-gavage, 87% of LBP-FITC was excreted via urine and feces, with the majority excreted through feces. This study provides technical and theoretical support for the in vivo detection of LBP and to further explore their absorption and distribution patterns.

Key words: Lycium barbarum polysaccharides; fluorescent labeling; pharmacokinetics