Fluorescence Labeling to Study the Distribution of Radix Puerariae lobatae Polysaccharide in Cells and Mice

Radix Puerariae lobatae polysaccharide (PLP1, M_w = 10.43 kDa), a novel polysaccharide isolated in our previous studies, possesses remarkable hepatoprotective properties. In this study, a highly sensitive fluorescent probe, namely, PLP1-tyrosine (TYR)-fluorescein isothiocyanate (FITC), was developed to investigate the distribution of PLP1 in vitro and in vivo. The fluorescent probe was characterized using fluorescence, high-performance gel permeation chromatography, infrared spectroscopy, ultraviolet spectroscopy, and nuclear magnetic resonance techniques, with a substitution degree of 0.53%. Toxicity assessments indicated that PLP1-TYR-FITC was nontoxic both in vitro and in vivo. In vitro, fluorescence microscopy revealed that PLP1-TYR-FITC may enter cells by endocytosis. In vivo, the distribution pattern of oral administration was as follows: small intestine > liver > kidney > spleen > stomach > heart > lung > brain. The distribution of intravenous administration was as follows: liver > small intestine > kidney > stomach > spleen > lung > heart > brain. FITC-labeled PLP1 was primarily distributed in the liver, supporting the hepatoprotective properties of PLP1. In summary, this study synthesized a PLP1 fluorescent probe to investigate PLP1 distribution in vitro and in vivo. Our findings lay the groundwork for further exploring the pharmacological mechanism of polysaccharides in Pueraria lobata.