AUTHOR=Yu Lulu , Qian Xunjia , Feng Yiheng , Yin Yujian , Zhang Xiao-Dan , Wei Qianqian , Wang Liyun , Rong Weiwei , Li Jie-Jia , Li Jun-Xu , Zhu Qing 

TITLE=Investigation of preclinical pharmacokinetics of N-demethylsinomenine, a potential novel analgesic candidate, using an UPLC-MS/MS quantification method

JOURNAL=Frontiers in Chemistry

VOLUME=Volume 11 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2023.1222560

DOI=10.3389/fchem.2023.1222560

ISSN=2296-2646

ABSTRACT=N-Demethylsinomenine (NDSM), the in vivo demethylated metabolite of sinomenine, has exhibited antinociceptive efficacy against various pain models and may become a novel drug candidate for pain management. However, no reported analytical method for quantification of NDSM in biological matrix is currently available, and the pharmacokinetic properties of NDSM are unknown. In the present study, an ultra-high performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS) method for quantification of NDSM in rat plasma was developed and utilized to examine the preclinical pharmacokinetic profiles of NDSM. The liquid-liquid extraction using ethyl acetate as the extractant was selected to treat rat plasma samples. The mixture of 25% aqueous phase (0.35% acetic acid-10mM ammonium acetate buffer) and 75% organic phase (acetonitrile) was chosen as the mobile phases flowing on a ZORBAX C18 column to perform the chromatographic separation. After a 6-minute rapid elution, NDSM and its internal standard (IS), metronidazole, were separated successfully. The ion pairs of 316/239 and 172/128 were captured for detecting NDSM and IS, respectively, using multiple reaction monitoring (MRM) under a positive electrospray ionization (ESI) mode in this mass spectrometry analysis. The standard curve met linear requirements within the concentration range from 3 to 1000 ng/mL, and the lower limit of quantification (LLOQ) was 3 ng/mL. The method was evaluated regarding precision, accuracy, recovery, matrix effect, and stability, and all the results met the criteria presented in the guidelines for validation of biological analysis method. Then the pharmacokinetic profiles of NDSM in rat plasma were characterized using this validated UPLC-MS/MS method. NDSM exhibited the feature of linear pharmacokinetics after intravenous (i.v.) or intragastric (i.g.) administration in rats. After i.v. bolus at three dosage levels (0.5, 1, and 2 mg/kg), NDSM showed the profiles of rapid elimination with mean half-life (T1/2Z) of 1.55~1.73 h, and extensive tissue distribution with volume of distribution (VZ) of 5.62~8.07 L/kg. After i.g. administration at three dosage levels (10, 20, and 40 mg/kg), NDSM showed the consistent peak time (Tmax) of 3 h and the mean absolute bioavailability of NDSM was 30.46%.