An analytical method entailing high-performance liquid chromatography coupled with electrochemical detection was developed for determining forsythiaside (FTS) in rat plasma. Rat plasma samples were prepared through efficient trichloroacetic acid deproteination. FTS and the internal standard were chromatographically separated on a reversed-phase core-shell silica C18 column (100 mm × 2.1 mm, i.d. 2.6 μm), with a mobile phase consisting of an acetonitrile-0.05-M phosphate solution (11.8:88.2, v/v), at a flow rate of 400 μL/min. The calibration curve, with r² > 0.999, was linear in the 20-1000 ng/mL range. The intra- and interday precision were less than 9.0%, and the accuracy ranged from 94.5% to 106.5% for FTS. The results indicated that the newly developed HPLC-EC method is more sensitive than previous reported methods using UV detection, and this new analytical method is applied successfully for the pharmacokinetic study of FTS. The hydrogel delivery system can efficiently improve bioavailability and mean residual time for FTS, as evidenced by the 2.5- and 6.3-fold increase of the area under the curve and the extension of the half-life, respectively.
Keywords: amperometric detection; forsythiaside; pharmacokinetics; thermoresponsive hydrogel.