Biopharmaceutics classification of puerarin and comparison of perfusion approaches in rats

The present study was conducted to characterize the biopharmaceutics classification system (BCS) category of puerarin in terms of intrinsic dissolution rate (IDR) and rat intestinal permeability and to investigate the poor intestinal absorption probably related to the drug metabolism in the gut wall of rats. Equilibrium solubility of puerarin was determined in various phosphate buffers and water, and IDR was estimated by measuring the dissolution of a non-disintegrating compact. Intestinal permeability (P-eff and P-blood) of puerarin was determined using the technology of in situ single-pass intestinal perfusion (SPIP) and intestinal perfusion with venous sampling (IPVS) in fasted rats. Metabolism of puerarin in intestinal tissue was tested by S9 incubation in vitro. The aqueous solubility of puerarin in phosphate buffers and water was good with a maximum solubility of 7.56 mg/mL at pH 7.4. Obtained IDR values of puerarin were in the range of 0.360-1.088 mg/min/cm(2), with maximum and minimum IDR value of pH 7.4 and pH 4.0, respectively. The P-eff was 1.252 x 10(-5) cm/s determined by SPIP and the P-blood was 0.068 x 10(-5) cm/s by IPVS in jejunum at puerarin 80 mu g/mL. The metabolism rate of puerarin determined by the intestinal S9 fraction indicated that the gut wall metabolism of puerarin is one cause of poor absorption. According to the proposed classification of drugs and the results obtained from equilibrium solubility, IDR, P-eff and P-blood, it is concluded that puerarin could be categorized IV drug of the BCS based on its low solubility and low intestinal permeability values. (C) 2014 Elsevier B. V. All rights reserved.