Stabilization of zeylenone in rat plasma by the presence of esterase inhibitors and its LC‐MS/MS assay for pharmacokinetic study

Six esterase inhibitors, namely EDTA·2Na⁺, NaF, phenylmethanesulfonyl fluoride, dichlorvos, bis‐nitrophenyl phosphate (BNPP) and thenoyltrifluoroacetone, and the mixture of NaF and BNPP, were evaluated for the stabilization of labile benzoate containing zeylenone in rat plasma. The mixture appeared to exhibit the most effectively stabilizing effect with the degraded content of zeylenone decreasing from >60% (in the absence of inhibitors) to <6%. Following the stabilization by the addition of NaF (5 mm ) and BNPP (5 mm ), the analytes in rat plasma were acidified by formic acid and extracted into ethyl acetate at 0°C. After chromatographic separation, the detection of zeylenone was performed on a 3200 Q‐Trap with positive ion electrospray mode, monitoring the ion transition m/z 383.2 → 105.0. The method was validated over the range from 2.68 to 1340 ng/mL with inter‐ and intra‐run precision for the quality control samples being less than 6.8%. The assay accuracy was within 100 ± 7.0%. The validated method was successfully applied to a pharmacokinetic study in rats after the intratracheal administration of zeylenone in free drug or polymeric micellar solutions. The results showed that the pulmonary absorption of zeylenone loaded in micelles was significantly retarded compared with that of free drug solutions. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of protoapigenone in rat plasma by high‐performance liquid chromatography with UV detection and its application in pharmacokinetic studies

A simple and sensitive HPLC method using UV detection was developed to determine the concentration of protoapigenone in rat plasma. Chromatographic separation was conducted on a C₁₈ column with a mobile phase consisting of an acetonitrile–methanol–aqueous phase (containing 0.2% acetic acid, pH 3.0) system at a flow rate of 1.0 mL/min. The UV detector was set at 248 nm. The calibration curve was linear over the range of 0.031–10.0 µg/mL. The lower limit of quantification was 31 ng/mL. The recoveries for plasma samples ranged from 70.3 to 82.5%. The intra‐ and inter‐day accuracy and precision fulfilled the international standards. This method was successfully applied to a pharmacokinetic study of protoapigenone in rats after oral administration of protoapigenone. It was shown that protoapigenone could be absorbed rapidly after oral administration and could reach the maximum concentration within 1 h. Copyright © 2013 John Wiley & Sons, Ltd.