Application of a liquid chromatography–tandem mass spectrometry method to the pharmacokinetics, tissue distribution and excretion studies of brazilin in rats

Brazilin is an important constituent of Caesalpinia sappan L., and has several bioactivities. In this study, a rapid and sensitive analytical method based on high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) has been developed for the determination of brazilin in rat plasma, urine, feces and tissues (brain, heart, liver, lung and kidney and spleen). Biological samples were processed with ethyl acetate containing 5% formic acid extraction, and salicylic acid (SA) was chosen as the internal standard (IS). The separation of brazilin was achieved on an Inspire C18 column (4.6 mm × 150 mm, 5 μm) with a mobile phase consisting of methanol/5 mM ammonium acetate (80:20, v/v). The MS/MS detection was carried out by monitoring the fragmentation of m/z 285.1 → 163.0 for brazilin and m/z 137.1 → 93.1 for SA on a triple quadrupole mass spectrometer. The total run time was only 5.0 min. The analyte showed good linearity over a wide concentration range (R2 > 0.995) and its lower limit of quantification was 2 ng/mL. The accuracy and precision ranged from 97.1 to 103.3% and 1.7 to 9.1%, respectively. Recoveries (78.9–93.8%) and matrix effects (81.0–97.8%) were satisfactory in all the biological matrices examined. Stability studies (86.4–99.8%) showed that brazilin was stable during the assay procedure and long-term storage. The assay was successfully applied to plasma pharmacokinetics, tissue distribution and excretion study of rats. The pharmacokinetic parameters, such as half-life, mean residence time, maximum concentration were determined. These preclinical data of brazilin would be useful for the clinical reference.