Pharmacokinetics, tissue distribution, and subacute toxicity of oral carrageenan in mice

Carrageenan (CGN) is a typical sulfated polysaccharide widely applied in the food and pharmaceutical industries. Its in vivo behavior plays vital roles in understanding structural and biological functional relationships. The lack of UV chromophores in highly sulfated polysaccharides presents a challenge for their in vivo behavior studies. Therefore, this study aimed to develop a fast and effective quantitative fluorescence method for investigating the pharmacokinetics and tissue distribution of CGN. Fluorescence isothiocyanate labeling of CGN (FCGN) and microplate reader-based measurements were developed and validated to study its pharmacokinetics. These results showed that the FCGN concentration peaked at 3 h, the mean residence time was 36.6 h, and the clearance rate was 0.1 L/h/kg. Most of the FCGN was excreted in the feces, while 9.2 % was excreted in the urine, suggesting absorption and metabolism. The pharmacokinetic parameters indicated that the FCGN was absorbed quickly, eliminated slowly, and could remain in the body for a sustained profile. Moreover, ex vivo imaging and quantification of FCGN in tissues revealed that FCGN accumulated in the liver and kidney. Furthermore, oral administration of CGN or KOs for 14 days led to changes in liver and kidney indices. Histological analysis of significant organs revealed hepatocyte necrosis in the liver, renal tubular vacuolization in the kidney, and incomplete colonic epithelial cells. The KOs had a more significant effect on inflammatory cell infiltration than did CGNs. These in vivo findings laid the foundation for the study and application of CGN in food and pharmaceutical applications.