Determination of the Pharmacokinetics and Tissue Distribution of Methyl 3,4-Dihydroxybenzoate (MDHB) in Mice Using Liquid Chromatography-Tandem Mass Spectrometry

Pharmacokinetics and tissue distribution of vigabatrin enantiomers in rats

Purpose

To investigate the pharmacokinetics and tissue distribution of VGB racemate and its single enantiomers, and explore the potential of clinic development for single enantiomer S-VGB.

Methods

In the pharmacokinetics study, male Sprague-Dawley rats were gavaged with VGB racemate or its single enantiomers dosing 50, 100 or 200 mg/kg, and the blood samples were collected during 12 h at regular intervals. In the experiment of tissue distribution, VGB and its single enantiomers were administered intravenously dosing 200 mg/kg, and the tissues including heart, liver, spleen, lung and kidney, eyes, hippocampus, and prefrontal cortex were separated at different times. The concentrations of R-VGB and S-VGB in the plasma and tissues were measured using HPLC.

Results

Both S-VGB and R-VGB could be detected in the plasma of rats administered with VGB racemate, reaching Cmax at approximately 0.5 h with t1/2 2-3 h. There was no significant pharmacokinetic difference between the two enantiomers when VGB racemate was given 200 mg/kg and 100 mg/kg. However, when given at the dose of 50 mg/kg, S-VGB presented a shorter t1/2 and a higher Cl/F than R-VGB, indicating a faster metabolism of S-VGB. Furthermore, when single enantiomer was administered respectively, S-VGB presented a slower metabolism than R-VGB, as indicated by a longer t1/2 and MRT but a lower Cmax. Moreover, compared with the VGB racemate, the single enantiomers S-VGB and R-VGB had shorter t1/2 and MRT, higher Cmax and AUC/D, and lower Vz/F and Cl/F, indicating the stronger oral absorption and faster metabolism of single enantiomer. In addition, regardless of VGB racemate administration or single enantiomer administration, S-VGB and R-VGB had similar characteristics in tissue distribution, and the content of S-VGB in hippocampus, prefrontal cortex and liver was much higher than that of R-VGB.

Conclusions

Although there is no transformation between S-VGB and R-VGB in vivo, those two enantiomers display certain disparities in the pharmacokinetics and tissue distribution, and interact with each other. These findings might be a possible interpretation for the pharmacological and toxic effects of VGB and a potential direction for the development and optimization of the single enantiomer S-VGB.

Evaluating Pharmacokinetic and Distribution Characteristics for A New Antitumor Activity Ortho-aryl Chalcone Compound of OC26 in Rats by LC-MS/MS Method

Introduction:

OC26, an ortho-aryl chalcone compound, shows excellent antitumor activity in vitro and vivo. However, the pharmacokinetic characteristics of OC26 have not been comprehensively reported. It is essential to investigate the correlation of pharmacological response.

Objective:

To further explore OC26, this study aims to develop an ultra-performance liquid chromatography- tandem mass spectrometric (UPLC-MS/MS) method to reveal the pharmacokinetics and distribution characteristics in rats of OC26.

Methods:

An UPLC-MS/MS method was developed to detect OC26 in plasma and various tissues. The protein precipitation method was applied to process the biological samples. After intravenous injection 12.5mg/kg of OC26 in rats, plasma and tissue samples were collected from rats and the method was applied to investigate pharmacokinetic and distribution characteristics of OC26.

Results:

Calibration curve samples of OC26 concentration range from 20 to 2000 ng/mL with the goodness of fit (r2> 0.99). The precisions for the method were within 12.3%, while the accuracies for the method were within ±11% (bias). The matrix effect had no influence on the accuracy and precision of the method. After intravenous injection 12.5mg/kg of OC26 in rats, OC26 was rapidly eliminated (t1/2=31.39±7.87min, MRT0→∞=15.03±2.55min) from rat plasma and widely distributed (Vd=4.83±0.96L/kg) in tissues. The highest concentration of OC26 was detected in the brain in which peak content (~8962.78ng/g at 15min) was over 5-fold higher than that of in other tissues, which prompted new potential targets in the brain. Besides, lung and heart also detected quite a high level of OC26. Benefited from quick elimination in the collected tissues and plasma, long-term accumulation was not observed as chronic toxicity might be less.

Conclusions:

This UPLC-MS/MS method was successfully applied to detect OC26 and provide a theoretical basis for the further study of OC26.

Excretion, Metabolism and Cytochrome P450 Inhibition of Methyl 3,4-Dihydroxybenzoate (MDHB): A Potential Candidate to Treat Neurodegenerative Diseases

BACKGROUND AND OBJECTIVES

Methyl 3,4-dihydroxybenzoate (MDHB) has the potential to prevent neurodegenerative diseases (NDDs). The present work investigated its excretion, metabolism, and cytochrome P450-based drug-drug interactions (DDIs).

METHODS

After intragastric administration of MDHB, the parent drug was assayed in the urine and faeces of mice. Metabolites of MDHB in the urine, faeces, brain, plasma and liver were detected by liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC-QTOF/MS). A cocktail approach was used to evaluate the inhibition of cytochrome P450 isoforms by MDHB.

RESULTS

The cumulative excretion permille of MDHB in the urine and faeces were found to be 0.67 ± 0.31 and 0.49 ± 0.44‰, respectively. A total of 96 metabolites of MDHB were identified, and all IC₅₀ (half-maximal inhibitory concentration) values of MDHB towards cytochrome P450 isoforms were > 100 μM.

CONCLUSIONS

The results suggest that MDHB has a low parent drug cumulative excretion percentage and that MDHB has multiple metabolites and is mainly metabolized through the loss of -CH₂ and -CO₂, the loss of -CH₂O, ester bond hydrolysis, the loss of -O and -CO₂, isomerization, methylation, sulfate conjugation, the loss of -CH₂O and -O and glycine conjugation, glycine conjugation, the loss of two -O groups and alanine conjugation, the loss of -CH₂O and -O and glucose conjugation, glucuronidation, glucose conjugation, etc., in vivo. Finally, MDHB has a low probability of cytochrome P450-based DDIs.