Simultaneous determination of eight bioactive compounds by LC-MS/MS and its application to the pharmacokinetics, liver first-pass effect, liver and brain distribution of orally administrated Gouteng-Baitouweng (GB) in rats

Abstract Only focusing on the circulating levels is insufficient for the comprehensive understanding of the physiological disposition of herbal medicine in vivo . Therefore, we conducted the comprehensive investigation on the in vivo dynamic process of orally administrated Gouteng - Baitouweng (GB), a classical herb pair with anti-Parkinson potentials. Serving as the technical base, a sensitive and selective liquid chromatography–tandem mass spectrometry method was established and validated in the plasma, liver and brain, for simultaneous determination of five alkaloids (rhynchophylline, isorhynchophylline, corynoxeine, isocorynoxeine and geissoschizine methyl ether) and three saponins (anemoside B4, anemoside A3 and 23-hydroxybetulinic acid). Following liquid-liquid extraction, favorable chromatographic behaviors of eight analytes were obtained on Waters Xbrigde C18 column within 13 min. This method elicited good linearity for the analytes at the concentration range of 0.3–1000 or 1.8–6000 ng/mL with favorable precision, accuracy and stability. Following oral administration of GB (25 g/kg) in rats, this method was applied to the quantitative analysis in the portal vein plasma, liver, systemic plasma, and brain. Consequently, anemoside B4 was of the highest exposure, followed by 23-hydroxybetulinic acid, anemoside A3, rhynchophylline and isocorynoxeine in vivo . Notably, three saponins were all observed with certain exposure in the brain, along with rhynchophylline at low levels. Besides, five alkaloids and 23-hydroxybetulinic acid underwent serious liver first-pass effect. Hence, the pharmacokinetics, liver first-pass effect, liver and brain distribution of ingredients in GB were clarified, which laid a solid foundation for interpreting its efficacy and safety.