ABSTRACT
OBJECTIVE: To determine the recovery rates of blood and brain microdialysis probes of acetylglutamine(NAG) and its decomposition products glutamic acid (Glu) and γ-aminobutyric acid (GABA) in vitro, and lay the foundation for the pharmacokinetic study of NAG in blood and brain. METHODS: The concentrations of NAG, Glu and GABA in blood and brain microdialysates were determined by LC-MS /MS and the probe recoveries were calculated. The in vitro recoveries of NAG, Glu and GABA were studied using positive dialysis and retrodialysis methods at different flow rates and concentrations. RESULTS: The in vitro recoveries of blood and brain probes of NAG, Glu and GABA were inversely proportional to the perfusate flow rates while independent of drug concentrations. The recovery rates obtained by positive dialysis and retrodialysis methods in vitro were approximately equal under the same condition, and were stable for at least 6 h. CONCLUSION: Retrodialysis method can be used to study the probe recovery of NAG, and microdialysis can be used for blood and brain pharmacokinetic study of NAG.
ABSTRACT
A high-performance liquid chromatography coupled with mass spectrometry (HPLC–MS) method was established for the separation and determination of acetyl-glutamine enantiomers (acetyl-L-glutamine and acetyl-D-glutamine) simultaneously. Baseline separation was achieved on Chiralpak AD-H column (250 mm × 4.6 mm, 5 μm). n-Hexane (containing 0.1% acetic acid) and ethanol (75:25, v/v) were used as mobile phase at a flow rate of 0.6 mL/min. The detection was operated in the negative ion mode with an ESI source. [M-H]? m/z 187.0540 for enantiomers and [M-H]? m/z 179.0240 for aspirin (IS) were selected as detecting ions. The linear range of the calibration curve for each enantiomer was 0.05–40 μg/mL. The precision of this method at concentrations of 0.5–20 μg/mL was within 7.23%, and the accuracy was 99.81%–107.81%. The precision at LOQ (0.05 μg/mL) was between 16.28% and 17.56%, which was poor than that at QC levels. The average extraction recovery was higher than 85% for both enantiomers at QC levels. The pharmacokinetics of enantiomers was found to be stereoselective. There was not chiral inversion in vivo or in vitro between enantiomers.
ABSTRACT
A high-performance liquid chromatography coupled with mass spectrometry (HPLC–MS) method was established for the separation and determination of acetyl-glutamine enantiomers (acetyl-L-glutamine and acetyl-D-glutamine) simultaneously. Baseline separation was achieved on Chiralpak AD-H column (250 mm × 4.6 mm, 5 μm). n-Hexane (containing 0.1% acetic acid) and ethanol (75:25, v/v) were used as mobile phase at a flow rate of 0.6 mL/min. The detection was operated in the negative ion mode with an ESI source. [M-H]? m/z 187.0540 for enantiomers and [M-H]? m/z 179.0240 for aspirin (IS) were selected as detecting ions. The linear range of the calibration curve for each enantiomer was 0.05–40 μg/mL. The precision of this method at concentrations of 0.5–20 μg/mL was within 7.23%, and the accuracy was 99.81%–107.81%. The precision at LOQ (0.05 μg/mL) was between 16.28% and 17.56%, which was poor than that at QC levels. The average extraction recovery was higher than 85% for both enantiomers at QC levels. The pharmacokinetics of enantiomers was found to be stereoselective. There was not chiral inversion in vivo or in vitro between enantiomers.