Determination of Esculetin in Rat Plasma by a Fast and Simple UPLC-MS/MS and its Application to a Pharmacokinetic Study

Esculetin is the compound of Cichorium glandulosum with major hepatoprotective effects. To further study the pharmacology of esculetin, it is necessary to investigate pharmacokinetics. In this study, we used UPLC-MS/MS to detect esculetin in rat plasma, and investigated its pharmacokinetics in rats. Apigenin was utilized as internal standard and acetonitrile precipitation method was used to process the plasma samples. Chromatographic separation was achieved using a UPLC BEH C18 column using mobile phase of acetonitrile-10 mmol/L ammonium acetate (containing 0.1 % formic acid) with gradient elution. Flow rate was set at 0.4 mL/min. Electrospray ionization (ESI) tandem mass spectrometry in multiple reaction monitoring (MRM) mode with positive ionization was applied. The results indicated that within the range of 2-500 ng/mL, linearity of esculetin in rat plasma was acceptable (r > 0.995), and the lower limit of quantification (LLOQ) was 2 ng/mL. Intra-day and inter-day precision RSD of esculetin in rat plasma were lower than 13%. Accuracy range was between 953 and 112.8 %, recovery was higher than 90.5 %, and matrix effect was between 98.7 and 107.4%. The method was successfully applied in the pharmacokinetics of esculetin in rats after oral and intravenous administration. The absolute bioavailability of the esculetin was 32.7% in rats.