Evaluation of Chito-Oligosaccharide (COS) in Vitro and in Vivo: Permeability Characterization in Caco-2 Cells Monolayer and Pharmacokinetics Properties in Rats

Chito-oligosaccharide (COS) had shown a variety of biological activities and potential biomedical implications. The present study investigated the pharmacokinetics, bioavailability, and in vitro absorption of COS with degrees of polymerization (DPs) 2–7 and explored the influence of DPs on them. From Caco-2 cell permeation studies, COS were low permeability compounds with no directional effects, suggesting a low in vivo absorption mediated by facilitation diffusion and paracellular absorption. After an intragastrical administration to rats, COS2 showed the highest systemic exposure in six oligosaccharides. The bioavailability of COS2–7 was 7.33%, 6.11%, 4.67%, 4.13%, 4.02%, 0.99%, respectively. Differences in bioavailability for each COS correlated to structural variations, with high DPs contributing to a decrease in bioavailability. In conclusion, COS could be absorbed by the intestinal tract both in vitro and in vivo. The very low oral bioavailability of COS could be due to low permeability. DPs can affect absorption and bioavailability of COS2–7. This study provided evidence for the absorption characteristics of COS2–7 to help us better understanding the pharmacological actions.