RESUMO
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.