Screening and Identification of Permeable Components of Radix et Rhizoma Rhei Extract by Use of Immobilized Artificial Membrane Chromatography

The objective of this work was to screen and identify permeable components of Radix et Rhizoma Rhei extract by use of immobilized artificial membrane chromatography (IAMC) then to investigate the intestinal absorption behavior of these components and the mechanism of absorption at three concentrations (0.3, 0.6, and 1.5 mg mL−1) by use of the in situ rat intestinal absorption model. The percentage absorption of permeable components was then correlated with their retention behavior by using mobile phases of three different pH (5.0, 6.0, and 7.0) containing buffers of two different ionic strength (10 and 50 mmol L−1). There was better correlation between percentage intestinal absorption and IAMC retention at pH 6.0 (r2 = 0.82) than at pH 5.0 (r2 = 0.64) or 7.0 (r2 = 0.74). The correlation coefficients suggest that most of the permeable components of Radix et Rhizoma Rhei were mainly absorbed by a passive diffusion mechanism. The four main permeable components were identified as rhein, aloe-emodin, chrysophanol, and emodin by comparison of chromatographic and spectrometric behavior with those of reference standards. IAMC seems useful as a promising rapid screening technique for identification of bioactive components in complex systems, e.g. traditional Chinese medicines.