Determination of baicalin in rat cerebrospinal fluid and blood using microdialysis coupled with ultra-performance liquid chromatography-tandem mass spectrometry

An in vivo microdialysis sampling method coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was employed for continuous simultaneous monitoring of unbound baicalin in rat blood and brain. Microdialysis probes were inserted into the jugular vein and brain cerebrospinal fluid (CSF) of Sprague-Dawley rats then, following administration of baicalin at doses of 24 mg/kg via the candal vein, samples were collected every 20 min and injected directly into the UPLC-MS/MS system. In vitro recoveries of the probes were 19.26% and 18.38%, while in vivo recoveries of the probes were 15.0% and 17.52% for blood and brain, respectively. This improved method offers a rapid quantitative procedure for the determination of baicalin with a retention time of only 1.6 min. The lower limit of quantification (LLOQ) and the lower limit of detection (LLOD) based on a signal-to-noise ratio of 5 were 2.37 and 0.1 ng/ml for anticoagulant citrate dextrose (ACD) solution, and 1.185 and 0.3 ng/ml for artificial cerebrospinal fluid (aCSF), respectively. The pharmacokinetics results indicated that baicalin could pass through the blood–brain barrier (BBB) and was detectable in brain dialysate. These in vivo microdialysis-based measurements provide a technique for simple sampling and rapid sensitive analysis of unbound baicalin in rat blood and CSF and for further application in pharmacokinetic studies.