Pharmacokinetic Comparative Study of Gastrodin and Rhynchophylline after Oral Administration of Different Prescriptions of Yizhi Tablets in Rats by an HPLC-ESI/MS Method

Pharmacokinetic characters of rhynchophylline (RIN), gastrodin (GAS), and gastrodigenin (p-hydroxybenzyl alcohol, HBA) were investigated after oral administration of different prescriptions of Yizhi: Yizhi tablets or effective parts of tianma (total saponins from Gastrodiae, EPT) and gouteng (rhynchophylla alkaloids, EPG). At different predetermined time points after administration, the concentrations of GAS, HBA, and RIN in rat plasma were determined by an HPLC-ESI/MS method, and the main pharmacokinetic parameters were investigated. The results showed that the pharmacokinetic parameters C (max) and AUC(0–∞) (P < 0.05) were dramatically different after oral administration of different prescriptions of Yizhi. The data indicated that the pharmacokinetic processes of GAS, HBA, and RIN in rats would interact with each other or be affected by other components in Yizhi. The rationality of the compatibility of Uncaria and Gastrodia elata as a classic “herb pair” has been verified from the pharmacokinetic viewpoint.