ABSTRACT
<p><b>OBJECTIVE</b>To determine the contents of L-enantiomer impurity in valaciclovir hydrochloride.</p><p><b>METHODS</b>Valaciclovir enantiomers were separated and determined by using chiral high performance liquid chromatography. Chromatographic conditions were as follows:CROWNPAK(®) CR(+) chiral column (4 mm×150 mm, 5 μm), detection wavelength:254 nm, mobile phase:water-methanol-perchloric acid (19:1:0.1), flow rate:0.75 ml/min, sample injection volume:10 μl.</p><p><b>RESULTS</b>D-valaciclovir was completely separated from L-enantiomer impurity. The contents of L-enantiomer impurity were 0.65%-2.62% on average in 8 batches of valaciclovir hydrochloride.</p><p><b>CONCLUSION</b>Enantiomeric impurity contents in each batch of products were all meet criteria of United States Pharmacopeia, which can be used in criteria of Chinese Pharmacopeia as references.</p>
Subject(s)
Acyclovir , Chromatography, High Pressure Liquid , Methods , Stereoisomerism , ValineABSTRACT
<p><b>OBJECTIVE</b>To study the stereoselective glucuronidation of carvedilol (CARV) by three Chinese liver microsomes.</p><p><b>METHODS</b>The metabolites of CARV were identified by a hydrolysis reaction with beta-glucuronidase and HPLC-MS/MS. The enzyme kinetics for CARV enantiomers glucuronidation was determined by a reversed phase-high pressure liquid chromatography (RP-HPLC) assay using (S)-propafenone as internal standard after precolumn derivatization with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosylisothiocyanate.</p><p><b>RESULTS</b>Two CARV glucuronides were found in three Chinese liver microsomes incubated with CARV. The non-linear regression analysis showed that the values of K(m) and V(max) for (S)-CARV and (R)-CARV enantiomers were (118+/-44) micromol/L, (2 500+/-833) pmol/(min.mg protein) and (24+/-7) micromol/L, (953+/-399) pmol/(min.mg protein), respectively.</p><p><b>CONCLUSION</b>These results suggested that there was a significant (P<0.05) stereoselective glucuronidation of CARV enantiomers in three Chinese liver microsomes, which might partly explain the enantioselective pharmacokinetics of CARV.</p>