Celastrol (CL), a compound isolated from Tripterygium wilfordii, possesses various bioactivities such as anti-tumor, anti-inflammatory and anti-obesity effects. Many new drug delivery systems of CL have been designed to overcome its poor water solubility and low bioavailability. However, few studies are available concerning its in vivo pharmacokinetics. In this study, a simple and sensitive LC-MS/MS method was developed and validated to determine CL in rat plasma using 18α-glycyrrhetinic acid as the internal standard. The separation of CL was performed on a Phenomenex Gemini C18 column (150 mm × 2 mm, 5 µm) following sample preparation using liquid-liquid extraction with the optimized extraction solvent of tert-butyl methyl ether and a small plasma sample volume of 50 μL. The analyte was quantitated under positive electrospray ionization and multiple reactions monitoring mode. The assay exhibited a good linearity in the concentration range of 0.5-500 ng/mL. The lower limit of quantification (LLOQ) was 0.5 ng/mL. The method was fully validated to meet the requirements for bioassay with accuracy of 91.1-110.0%, precision (RSD %) of less than 9.1 %, extraction recovery of 63.5-74.7%, and matrix effect of 87.3-101.2%. The developed method was successfully applied to the pharmacokinetic evaluation of CL-encapsulated silk fibroin nanoparticles (CL-SFNP). The results show, after intravenous (IV) and oral (PO) administration of equivalent CL (1 mg/kg and 3 mg/kg, respectively) in rats, the AUC values of CL were 8646.1±1998.9 ng/mL·h after IV dosing and 1065.5±494.6 ng/mL·h after PO dosing for CL-SFNP, which were significantly (P<0.05) higher than those for pure CL (4697.7±723.0 ng/mL·h and 441.9±82.6 ng/mL·h, respectively). The dose-normalized oral bioavailability of CL significantly (P<0.05) increased from 3.1% for pure CL to 7.6% for CL-SFNP.

Citation Format: Shuyu Zhan, Amy Paik, Felicia Onyeabor, Baoyue Ding, Sunil Prabhu, Jeffrey Wang. Development and validation of an LC/MS/MS method for the determination of celastrol in rat plasma and its application to the pharmacokinetic evaluation of celastrol-encapsulated silk fibroin nanoparticles [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6252.