Simultaneous Determination and Pharmacokinetic Comparisons of Aloe-Emodin, Rhein, Emodin, and Chrysophanol After Oral Administration of These Monomers, Rhei Rhizoma and Chaiqin-Chengqi-Tang, to Rats

A study was conducted to compare the pharmacokinetics of aloe-emodin, rhein, emodin, and chrysophanol after oral administration of these monomers, Rhei Rhizoma and Chaiqin-Chengqi-Tang, to rats. Separation of the monomers in rat plasma was accomplished on a YMC C18 stationary phase (4.6 × 150 mm, 5 µm) and a mobile phase of methanol-water containing 0.2% acetic acid (70:30, v/v), with a UV detector setting at 254 nm. The calibration curves for the four compounds were linear in an appropriate concentration ranges. The intra- and inter-day assay coefficients in plasma were less than 10.96% and the recoveries of the method were higher than 90.0%. The validated method was successfully applied in the aforementioned pharmacokinetic study. The results show that the pharmacokinetics of aloe-emodin, rhein, emodin, and chrysophanol in the rat is different when given orally alone, as a Rhei Rhizoma mixture, or in a Chaiqin-Chengqi-Tang prescription. This may be due to unidentified herb-herb or herbal constituent interaction mechanisms.