RESUMEN
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.
RESUMEN
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.
RESUMEN
NG-nitro-D-arginine (D-NNA) produced pressor responses in rats by acting via chiral inversion intoNG-nitro-L-arginine (L-NNA), an inhibitor of nitro oxide synthase. The present investigation aimed to study the roleof the D-amino acid oxidase (DAAO) in chiral inversion of D-NNA and the relationship between DAAO activitieson various D-amino acids and their inversion rate. Benzoate (400 mg/kg) or creatinine (400 mg/kg), two inhibitorsof DAAO, blocked D-NNA-induced pressor responses in rats. Furthermore, the addition of the pure DAAOsignificantly potentiates L-NNA production rate in kidney homogenates by approximately 2-folds. The in vivo andin vitro results suggested that DAAO plays an essential role in the pressor responses elicited by D-NNA.Moreover, crude DAAO solution from the kidney showed marked selection (the maximal ratio of Kcat/Km wasnearly 15 times) on different D-amino acids that exhibited similar chiral inversion rate in vivo, suggesting that otherenzymes, such as transaminase, are also required for the entire process of D-NNA chiral inversion.
RESUMEN
Aim: To explore pharmacokinetics of NG-nitro-D-arginine (D-NNA)and NG-nitro-L-arginine (L-NNA)in conscious rats. Methods: The plasma concentration of D-NNA and L-NNA were determined by chiral ligand exchange method with capillary electrochromatography (CEC). Pharmacokinetic parameters were obtained using non-compartment model and were fitted using a computer program DAS. Results: The metabolism of D-NNA and L-NNA exhibited significant isomeric selectivity. The CL and T1/2 of D-NNA and D-NNA were(0.46 ± 0.02) ml·h-1·kg-1 vs (0.17 ± 0.03) ml·h-1·kg-1 (P < 0.05) and (1.44 ± 0.28) h vs (3.48 ± 0.41) h (P < 0.05), respectively. Unidirectional chiral conversion rate of D-NNA to L-NNA was (50.03 ± 8.5)%. Conclusion: The stereoselective pharmacokinetics of N G-nitro-arginine observed maybe due to the unidirectional chiral inversion of D-NNA to L-NNA.