OBJECTIVETo study the intestinal absorption mechanism of traditional Chinese medicine monomer syringopicroside in rats.

METHODThe 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.

RESULTThe 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).

CONCLUSIONSyringopicroside 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.