ABSTRACT
Aim To investigate the absorption characteristics of gallic acid in the intestine, and to provide a theoretical basis for improving the bioavailability of tannins. Methods Single-pass intestinal perfusion (SPIP) model was used for rat in situ and HPLC to determine the concentration of gallic acid. The absorption rate constant Ka and effective apparent permeability coefficient Peff of gallic acid in each intestinal segment were calculated. The effects of different intestinal segments, drug concentrations, pH value, P-glycoprotein (P-gp), and multidrug resistance protein2 (MRP2) on intestinal absorption were assessed. Results The absorption rate constant (Ka) of gallic acid decreased following the sequence of jejunum > duodenum > ileum ≈ colon. With the increase of drug concentration, there was no significant difference in the absorption of gallic acid. The acidic environment (pH 5. 5) was conducive to the absorption of gallic acid. After the addition of P-gp and MRP2 inhibitors, the absorption of gallic acid was significantly different from that without P-gp and MRP2 inhibitors (P < 0. 05). Conclusions Gallic acid can be well absorbed in the intestine of rats, and is best absorbed in jejunum. The absorption mechanism is determined to be passive diffusion. The gallic acid absorption process is affected by the efflux of P-gp and MRP2, which may be the P-gp and MRP2 substrates.
ABSTRACT
To study the in vivo intestinal absorption kinetics of phloridzin in rats. The absorption of phloridzin in the small intestines and colon of rats was investigated using an in vivo single-pass perfusion method and the drug concentration was measured by HPLC. The effects on intestinal absorption of different drug concentration and P-glycoprotein (P-gp) inhibitor were conducted. The results showed that the phloridzin could be absorbed in whole intestine, but more fully in the jejunum and colon segment,poorly absorbed in the duodenum and ileum. The absorption rate constant (Ka) and the apparent absorption coefficient（Papp）of phloridzin decreased following the sequence of jejunum> colon > duodenum > ileum. Absorption parameters of phloridzin had no significant difference at different concentration (5.14, 10.28, 20.56 mg•L⁻¹) . The saturate phenomena was not observed under the test range of drug concentration, and the absorption mechanism may be the passive diffusion transport.There had a significant difference in Ka and Papp values between P-gp inhibitor and no P-gp inhibitor groups. Phloridzin may be the substrate of P-gp.
ABSTRACT
To investigate the changes in intestinal absorption of ginsenosides Rg₁, ginsenosides Re and ginsenosides Rd after combined administration of Ginseng Radix et Rhizoma extract and Acori Tatarinowii Rhizoma, in order to confirm whether the combined administration is scientific and rational, and provide experimental basis for pharmaceutical studies of the formula. An in vivo single-pass perfusion method was performed to study the effect of various concentrations of ginsenosides Rg₁, ginsenosides Re, ginsenosides Rd on the intestinal absorption at duodenum, jejunum, ileum and colon. The concentrations of ginsenosides Rg₁, ginsenosides Re, ginsenosides Rd were determined by RP-HPLC.The absorption rate constant (Ka) and the apparent absorption coefficient(Papp) of ginsenosides Rg₁, ginsenosides Re, ginsenosides Rd were calculated.The result showed that ginsenosides Rg₁, ginsenosides Re, ginsenosides Rd had a high absorption rate on upper portion of the small intestine. The drug concentration had not significantly impact on the absorption rate, suggesting that ginsenosides Rg₁, ginsenosides Re, ginsenosides Rd were absorbed via passive diffusion.Volatile oil of Acori Tatarinowii Rhizoma had obvious effect in enhancing intestinal absorption of ginsenosides Rg₁, ginsenosides Re, ginsenosides Rd, indicating that the combined administration of Ginseng extract and Acorus tatarinowii Schott is scientific and rational.
ABSTRACT
Objective: To investigate the intestinal absorption characteristics of α-hederin and to explore the causes of poor bioavailability. Methods: In vivo single-pass perfusion model was used and the concentration of α-hederin was determined by HPLC. The effects of intestinal segment, drug concentration, pH value, gut microflora, and P-gp inhibitor on the intestinal absorption of the drug were investigated. Results: The absorption rate constant (Ka) of α-hederin decreased following the sequence of ileum > colon > jejunum > duodenum. Absorption parameters of α-hederin had no significant difference at different concentration of 75, 150, and 300 μg/mL and those increased with the increase of pH value. The intestinal flora which were disrupted may affect the absorption of α-hederin. There was no significant difference in Ka and Peff values between P-gp inhibitor and no P-gp inhibitor groups. Conclusion: α-Hederin can be absorbed in whole intestine, but better in lower intestine. The saturate phenomena was not observed under the test range of drug concentration, and the absorption mechanism may be the passive diffusion transport. The absorption can be better under basic condition. The absorption is significantly affected by the intestinal flora and α-hederin is not the substrate of P-gp.