Comparative Pharmacokinetics Study of Icariin and Icariside II in Rats

To explore the pharmacokinetic properties of icariin (ICA) and icariside II (ICA II) following intragastric and intravenous administration in rats, a rapid and sensitive method by using ultra-performance liquid chromatography–tandem mass spectroscopy (UPLC-MS/MS) was developed and validated for the simultaneous quantification of ICA and ICA II in rat plasma. The quantification was performed by using multiple reaction monitoring of the transitions m/z 677.1/531.1 for ICA, 515.1/369.1 for ICA II and 463.1/301.1 for diosmetin-7-O-β-d-glucopyranoside (IS). The assay showed linearity over the concentration range of 1.03–1032 ng/mL, with correlation coefficients of 0.9983 and 0.9977. Intra- and inter-day precision and accuracy were within 15%. The lower limit of quantification for both ICA and ICA II was 1.03 ng/mL, respectively. The recovery of ICA and ICA II was more than 86.2%. The LC-MS/MS method has been successfully used in the pharmacokinetic studies of ICA and ICA II in rats. The results indicated that 91.2% of ICA was transformed into ICA II after oral administration by rats, whereas only 0.4% of ICA was transformed into ICA II after intravenous administration. A comparison of the pharmacokinetics of ICA and ICA II after oral administration revealed that the C(max) and AUC(0–t) of ICA II were 3.8 and 13.0 times higher, respectively, than those of ICA. However, after intravenous administration, the C(max) and AUC(0–t) of ICA II were about only 12.1% and 4.2% of those of ICA. These results suggest that ICA and ICA II have distinct pharmacokinetic properties, and the insights obtained facilitate future pharmacological action studies.