Comparison of two approaches of intestinal absorption by puerarin

Everted gut sac (EGS) and in situ single-pass intestinal perfusion (SPIP) have been widely used in the study of drug absorption and biopharmaceutical classification systems (BCS). Furthermore, they could also be applied in the research of drug intestinal first-pass metabolism. Since most of Chinese herbal medicines (CHMs) are orally administrated, it is necessary to study the permeability of active ingredients of CHMs. Thus, we attempted to apply the EGS and SPIP models to study the permeability of puerarin, one of the active marker compounds (AMCs) of Puerariae Radix.

In the present study, three rat models of ex vivo and in situ, EGS, SPIP, and in situ intestinal perfusion with venous sampling (IPVS), were established to determine the permeability coefficient of puerarin. The apparent permeability coefficient (Papp) was obtained by EGS. The SPIP model was used to determine the effective permeability coefficient (Peff) in different intestinal segments. The blood permeability coefficient (Pblood) was determined by IPVS. Puerarin concentration of perfusion and blood samples were measured by HPLC.

Puerarin could filter into EGS incubated in aqueous extract of Puerariae Radix or puerarin solution. In the SPIP experiment, the concentration effect on Peff was observed in the ileum, but not in the other three intestinal segments. The Pblood was 0.068±0.002×10(-5)cm/s and was 16-fold lower than the Peff (1.114±0.153×10(-5)cm/s) in the IPVS experiment at 80μg/mL puerarin. As expected, the Peff (1.24±0.11×10(-5)cm/s) in SPIP did not differ from the Peff in IPVS. The Papp was 0.199×10(-5)cm/s at 1200μg/mL puerarin, 10-fold lower than Peff (2.047±0.116×10(-5)cm/s) in SPIP.

Three models for permeability were successfully practiced in the study of puerarin absorption and our research strategy will be useful for herbal constituent absorption in the future.