Development and validation of an LC-ESI-MS/MS method for the quantitation of hemslecin A in rhesus monkey plasma and its application in pharmacokinetics.

In this study, a new LC-ESI-MS/MS-based method was validated for the quantitation of hemslecin A in rhesus monkey plasma using otophylloside A as internal standard (IS). Hemslecin A and the IS were extracted from rhesus monkey plasma using liquid-liquid extraction as the sample clean-up procedure, and were subjected to chromatography on a Phenomenex Luna CN column (150 × 2.0 mm, 3.0 µm) with the mobile phase consisting of methanol and 0.02 mol/mL ammonium acetate (55:45, v/v) at a flow rate of 0.2 mL/min. Detection was performed on an Agilent G6410B tandem mass spectrometer by positive ion electrospray ionization in multiple reaction monitoring mode, monitoring the transitions m/z 580.5 [M + NH4 ](+) → 503.4 and m/z 518.2 [M + NH4 ](+) → 345.0 for hemslecin A and IS, respectively. The assay was linear over the concentration range of 0.5-200 ng/mL and was successfully applied to a pharmacokinetic study in rhesus monkeys.

[Study on in vivo pharmacokinetics of cucurbitacin injection in rats].

To establish a method for the determination of cucurbitacin in plasma samples, in order to study the in vivo pharmacokinetic characteristics of cucurbitacin in rats. Rats were intravenously injected with cucurbitacin. With diphenhydramine as the internal standard (IS), the plasma concentrations of cucurbitacin in rat plasma at different time points were determined by liquid chromatography tandem mass spectrometry (LC-MS/MS). With electrospray ionization source, the positive ion detection in the multiple reaction monitoring mode was conducted to determine the ion-pairs for target compound and IS were m/z 503.2/113.1 and m/z 256.0/167.2, respectively. Agilent ZOBAX SB-C18 column (2.1 mm x 50 mm, 1.8 microm) was adopted and eluted with methanol and 0.1% formic acid (55:45), and the flow rate was 0.2 mL x min(-1). DAS 2.0 software was applied to fit the blood concentration and calculate corresponding pharmacokinetic parameters. The rats were intravenously injected with cucurbitacin at the concentration of 3.0 mg x kg(-1). The target blood quality concentration show good linear relations within the range of 10.5-3 150 microg x L(-1) (R2 = 0.996), the lower limit of the standard curve was 10.5 microg x L(-1), and the signal to noise ratio S/N = 12. Intra- and inter-day precisions RSD was less than 6.9% and 14%, respectively; The accuracy RE ranged between 0.20% and 3.7%; The extraction recoveries ranged between 92.7% and 97.1%. Regarding the pharmacokinetic parameters of tail intravenous injection of cucurbitacin, AUC (0-t) was (811.615 +/- 111.578) microg x h x L(-1), (t1/2) was (1.285 +/- 1.390) h, CL was (3.627 +/- 0.487) L x h x kg(-1), and V(d) was (6.721 +/- 7.429) L x kg(-1). In this study, researchers established a simple, accurate, sensitive and highly specific method for determining the blood concentration of cucurbitacin, and reported the in vivo pharmacokinetic characteristics of cucurbitacin in rats for the first time.

Development and validation of a quantification method for cucurbitacins E and I in rat plasma: Application to population pharmacokinetic studies.

Cucurbitacin E is a potential drug candidate due to its anticancer activity, recognition of its molecular targets, and synergism with other drugs used for cancer treatment. However, the use of cucurbitacin E in clinical practice is not possible because of important knowledge gaps in its preclinical and clinical pharmacokinetic characteristics. Cucurbitacin E is hydrolyzed to cucurbitacin I in plasma and in human liver microsomes. The aim of this study was to evaluate the population pharmacokinetics of cucurbitacin E and of its metabolite cucurbitacin I in rats. The method for the sequential analysis of cucurbitacins E and I in rat plasma was developed using LC-MS/MS. Plasma aliquots of 50µL were deproteinized with acetonitrile and clobazam was added as internal standard. The extracts were injected into an RP-18 column and eluted with a mobile phase consisting of a mixture of acetonitrile:water:methanol (32:35:33, v/v/v). The method was precise and accurate, showing linearity in the range of 1-100ng cucurbitacin E/mL plasma and of 0.4-200ng cucurbitacin I/mL plasma. The method was applied to the pharmacokinetic evaluation of cucurbitacin E administered intravenously to male Wistar rats (1mg/kg). Serial blood samples were collected up to 24h after administration. The plasma concentrations of cucurbitacin E were quantified up to 16h, while the plasma concentrations of cucurbitacin I remained below the limit of quantification. A population pharmacokinetic model was developed for cucurbitacin E using the NONMEM program, with adequate goodness of fit and predictive performance. The following pharmacokinetic parameters were obtained: release time of 0.45h, volume of distribution of 27.22L, clearance of 4.13L/h, and elimination half-life of 4.57h.