Objective: To study the intestinal absorption mechanism of traditional Chinese medicine monomer syringopicroside in rats.
Method: The in situ rat single-pass intestinal perfusion model was established to detect the concentration of syringopicroside by HPLC. The absorption at different intestine segments in rat and the influence of concentration, pH and P-glycoprotein inhibitors of the drug solution on the absorption of syringopicroside were also observed.
Result: The absorption rate constant (K,) of syringopicroside at duodenum, jejunum, ileum, and colon were 0.00255, 0.00630, 0.00900, 0.00799 min- , respectively; Ka from intestine at syringopicroside concentration of 0.090, 0.180, 0.360 g x L(-1) were 0.00370, 0.00708, 0.00694 min(-1), respectively; and Ka at pH of 7.4, 6.8 and 5.0 were 0.00733, 0.00747, 0.00362 min(-1), respectively. P-glycoprotein inhibitor on the intestinal absorption of syringopicroside showed significant influence (P < 0.05).
Conclusion: Syringopicroside is well absorbed at the lower small intestine. When the drug concentration is low, the absorption rate constant is low, where as Ka increases at medium and high concentrations; the Ka is low at pH 5.0 and increases at pH 6.8 and pH 7.4. Syringopicroside is proved to be a substrate of P-glycoprotein.