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In this study, daphnetin and its major metabolites in the intestinal wall of rats were identified by liquid chromatography and quatrupole-time of flight mass spectrometry. Perfusion fluid of duodenum, jejunum, ileum and colon were collected separately for 2 hours from the rat intestine following perfusion with daphnetin. The metabolites of daphnetin in the perfusion fluid of different intestine segments were analyzed by the liquid chromatography and quatrupole-time of flight mass spectrometry. It is shown that the parent drug daphnetin and four metabolites were found in the perfusion fluid of duodenum, jejunum and ileum. However, no metabolites were found in the colon. Among the four metabolites, two daphnetin sulfates (m/z 257) were first discovered as the phase II metabolites of daphnetin in rats, which revealed a new way of daphnetin metabolism in rats.

This study aimed to investigate the effects of concentration, intestinal section and borneol on the intestinal absorption of salvianolic acids. The experiment not only studied the intestinal absorption properties of three concentrations of rosmarinic acid, salvianolic acid B and salvianolic acid A at duodenum, jejunum and ileum, but also of salvianolic acids compatible with borneol at different concentrations using single-pass intestinal perfusion model in rat with phenol red as the marker. The results showed that salvianolic acids was stable under weak-acid condition and affected by metabolism enzyme; The Peff and Ka significantly different among three concentrations of rosmarinic acid and salvianolic acid B, whose intestinal absorption were saturated in high concentration, suggesting that the transport mechanisms of rosmarinic acid and salvianolic acid B were similar to active transport or facilitated diffusion; However, there was inconspicuousness in the Peff and Ka of salvianolic acid A at different concentrations, whose absorption was not saturated in high concentration, indicating that the transport mechanisms of salvianolic acid A was passive diffusion; The Peff and Ka in the ileum obviously higher than those in the duodenum and jejunum, namely the ileum was the best absorption section; When concentration of borneol increased, the enhancing effect of intestinal absorption of salvianolic acids increased, but significantly decreased when borneol increased to some degree. The enhancing effect of medium borneol concentration was the optimum. This implied that borneol can enhance the intestinal absorption of salvianolic acids, and the capacity of enhancing effect was influenced by the concentration of borneol.

This study is to investigate the effects of concentration, intestinal section, pH, paracellular route, substrate/inhibitor of enzyme (CYP3A) and proteins (P-gp, MRP2, SGL1) on the absorption of forsythoside A. The absorption of three concentrations (2.6, 5.2, and 10.4 microg x mL(-1)) of forsythoside A in different intestinal segments was studied with phenol red as the marker by rat circulation in situ. The results showed that the residue of forsythoside A with different concentrations had little significant difference from that obtained after perfusing via duodenum, jejunum, ileum and colon, which indicated that the absorption of forsythoside A was passive diffusion and had no difference in different segments of rat intestine. The residue of forsythoside A increased to 466.160 and 463.429 microg respectively when cyclosporine (4 microg x mL(-1)) or midazolam (50 micromol x L(-1)) was added to the circulation fluid, which showed significant difference compared to the control group (P < 0.05). Moreover, the residue of forsythoside A showed a tendency of increase with the increase of cyclosporine or midazolam. When digoxin (50 micromol x L(-1)) or EDTA (10 microg x mL(-1)) was added to the circulation fluid, the residue of forsythoside A decreased to 325.110 and 369.888 microg respectively, which showed significant difference as compared to the control group (P < 0.05). Besides, the residue of forsythoside A showed a tendency of reduction with the increase of digoxin or EDTA. However, there is no significant change in the absorption of forsythoside A when the different concentrations of mannitol were added to the circulation fluid. The results above indicated that the absorption of forsythoside A was mainly passive diffusion and involved paracellular route at the same time. In addition, the substrates of P-gp or CYP3A had dose-dependent effect on the absorption of forsythoside A.

The aim of the study is to investigate rat intestinal absorption behavior of three main active components, schisandrol A, schisandrin A and schisandrin B in Schisandra chinensis Baill extracts in intestine of rats. With phenol red as the indicator, in situ single pass intestinal perfusion (SPIP) model was used and the concentrations of three main active components in perfusion solution of different intestinal segments (duodenum, jejunum, ileum, and colon) were determined by HPLC in combination with diode array detection. The results showed that the absorption rate constant (Ka) and effective permeability values (Peff) of three main active components in Schisandra chinensis Baill extracts had significant difference (P < 0.05) at different concentrations of perfusion solution, the Ka and Peff first increased and then decreased with the increase of drug concentration, the middle concentration was higher than those of the other two concentrations. The saturate absorption phenomena were observed, and it suggested that the transport mechanisms of three main active components in vivo were similar to active transport or facilitated diffusion. Three active components can be well absorbed in all of the intestinal segments, while duodenum is the best absorption region. The Ka and Peff of three active components in jejunum and ileum had no significant difference (P > 0.05). The absorption of the three active components displayed significant difference (P < 0.05) at different intestinal segments of rats. Schisandrin A had the best absorption in duodenum. The Ka and Peff among three active components were sequenced as follows: schisandrin A > schisandrin B > schisandrol A in other intestinal segments, and there is significant difference (P < 0.05) between them.

This study investigated the effects of concentration, intestinal section, pH and P-gp on the absorption of daphnetin. The absorptions of three concentrations (10, 20, 40 microg x mL(-1)) of daphnetin in different intestinal segments were studied with phenol red as the marker by in situ rats single pass perfusion model. The results showed that daphnetin was stable under pH 6.0 condition and little affected by metabolism enzyme. There was upgrade tendency between the Peff of duodenum, jejunum, ileum and colon in different concentration of daphnetin, and it has obvious difference between the high concentration and low concentration in jejunum and colon, which indicated that the absorption of daphnetin was passive diffusion and no difference in different segments of rat intestine. However, compared with colon, the absorption of small intestine was better significantly (P < 0.05). Daphnetin may be not a substrate of P-gp as verapamil had not significantly affected the absorption of daphnetin in different intestinal segments of rats.