Determination of chrysotoxine in rat plasma by liquid chromatography–tandem mass spectrometry and its application to a rat pharmacokinetic study

• Chrysotoxine is a naturally occurring bibenzyl and shows neuroprotective effects.
• A LC–MS/MS method was developed for quantification of chrysotoxine in rat plasma.
• Liquid–liquid extraction was used for pretreatment and the LLOQ was 0.5 ng/mL.
• Pharmacokinetics after a single p.o. and i.v. administration was studied in rats.
• Chrysotoxine shows rapid excretion and low bioavailability in rats.

Chrysotoxine (CTX), a naturally occurring bibenzyl compound isolated from Dendrobium species, has been reported to have neuroprotective effects. To evaluate its pharmacokinetics in rats, a rapid, sensitive and specific high performance liquid chromatography–tandem mass spectrometric (HPLC–MS/MS) method has been developed and validated for the quantification of CTX in rat plasma. Samples were pretreated using a simple liquid–liquid extraction with ethyl acetate and the chromatographic separation was performed on a C18 column with acetonitrile–water (90:10, v/v) as the mobile phase. CTX and the internal standard (wogonin) were detected using a tandem mass spectrometer in positive multiple reaction monitoring mode. Method validation revealed excellent linearity over the range 0.5–1000 ng/mL together with satisfactory intra- and inter-day precision, accuracy and recovery. Stability testing showed that CTX spiked into rat plasma was stable for 8 h at room temperature, for up to two weeks at −20 °C, and during three freeze–thaw cycles. Extracted samples were also observed to be stable over 24 h in an auto-sampler. The method was successfully used to investigate the pharmacokinetic profile of CTX after oral (100 mg/kg) and intravenous (25 mg/kg) administration in rats. CTX showed rapid excretion and low bioavailability in rats.