A sensitive bioanalytical method for quantitative determination of resiniferatoxin in rat plasma using ultra-high performance liquid chromatography coupled to tandem mass spectrometry and its application in pharmacokinetic study

Resiniferatoxin (RTX) is a daphnane diterpene isolated from the latex of Euphorbia resinifera O. Berg, a potent activator of transient receptor potential vanilloid 1 (TrpV1), with a potency 10(3) -10(5) times greater than pure capsaicin. Intravenous administration of RTX at very low concentration improves urodynamic parameters in patients with neurogenic detrusor overactivity and also reduces bladder pain in patients. Herein, a simple, rapid, selective and sensitive method for determination of RTX with silydianin as an internal standard was developed using ultra-high performance liquid chromatography coupled to tandem mass spectrometry with electrospray ionization source (UHPLC-ESI-MS/MS) in multiple reaction monitoring mode. The mass spectrometer was operated in positive electrospray ionization ((+) ESI) mode. Multiple reaction monitoring (MRM) mode was performed with ion pairs of m/z: 629.23 -> 283.2 for RTX and 483.24 -> 153.1 for IS. The limit of detection achieved in this method for RTX was 0.05 ng/mL and had good linearity in calibration range of 0.2-50 ng/mL ( r(2) = 0.99). Precision and accuracy values were found to be < 15% (within acceptable limit), extraction recovery ( >= 88.2%), matrix effect ( >= 89.7%) and stability were in accordance with the bioanalytical guidelines. The sensitivity of this bioanalytical method supported the successful pharmacokinetic evaluation of RTX on rat plasma (2.5 mu g/kg dose; i.v.) and has demonstrated pharmacokinetic parameters V-d and AUC(0-infinity) as 191.0 +/- 71.31 mL/kg and 981.6 +/- 137.40 min*ng/mL, respectively. The clearance was found to be 2.6 +/- 0.38 mL/min/kg and halflife was 53.6 +/- 23.51 min. This efficient, rapid and reliable method promises the quantification at low concentration of RTX, allowing determination of the pharmacokinetic profile, which is essential in future drug delivery and clinical application. (C) 2018 Elsevier B.V. All rights reserved.