Determination of Paeoniflorin in Rat Plasma by Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry and its Application to a Pharmacokinetic Study.
In this study, a rapid and highly sensitive ultra-high performance liquid chromatography-tandem mass spectrometry method was established for the quantification of paeoniflorin in rat plasma. The analyte and the internal standard (IS), hyperoside, were extracted from rat plasma via liquid-liquid extraction with ethyl acetate. LC separation was carried on a Phenomenex Luna C18 column within 2.5 min. Quantitation was performed on a triple quadrupole mass spectrometer employing electrospray ionization and operated in the multiple reaction monitoring and negative ion modes. The precursor to product ion transitions monitored for paeoniflorin and the IS were m/z 524.8→449.0 and 463.1→300.0, respectively. The assay was validated with a linear range of 0.02~25.6 μg/mL for paeoniflorin. The intra- and inter-day precisions (relative standard deviation%) were within 9.7%, and the recoveries were greater than 65.2%. Paeoniflorin was proven to be stable during all sample storage, preparation and analytical procedures. The method was successfully applied to a pharmacokinetic study of the Baixiangdan Capsule in eight female rats.
Preparation, physicochemical characterization and pharmacokinetics of paeoniflorin-phospholipid complex.
In order to enhance lipophilicity and oral bioavailability of paeoniflorin (PF), this study developed paeoniflorin-phospholipid complex (PF-PLC) by solvent-evaporation method. The optimum preparation technology of PF-PLC was screened by the combination of single factor and orthogonal experiment. The physicochemical properties of PF-PLC were evaluated via differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and oil-water partition coefficient study (lgP). The result of FTIR spectra indicated that there was some strong hydrogen bond interaction and good compatibility between the phospholipid molecule and PF in the complex. DSC and XRD structure analysis showed that PF was in form of amorphous structure in PF-PLC, and lgP of PF-PLC was enhanced, suggesting that the lipophilicity of PF-PLC was higher than that of PF. In vitro release of PF-PLC showed slower release than PF solution with its cumulative release rate of 93.81% at 24 h compared to 93.43% of PF at 1.5 h. In pharmacokinetic experiments, the AUC and Cmax of the PF-PLC were 1.97-fold and 2.5-fold higher than PF solution. These results suggested that PF-PLC could enhance lipophilicity and oral bioavailability of PF and provide a promising delivery system for the application of PF.
Phase characterisation of simulated high burn-up UO2 fuel
Abstract To determine the lattice constant variation with burn-up and the oxidation behaviour at high temperatures, simulated UO2-spent fuels with burn-ups up to 200 GWd tM−1 were prepared by cold pressing and sintering and characterised by X-ray diffraction analysis and thermogravimetry. The fcc-lattice parameter of the sintered samples determined at room temperature, showed a continuous decrease with the simulated burn-up. During oxidation the conversion of the simulated fuels to the (U,FP)4O9 and (U,FP)3O8-type phases was strongly delayed when the simulated burn-up exceeded 80 GWd tM−1. Also, at high burn-ups (>100 GWd tM−1), large fractions of the (U,FP)4O9-type phase remained untransformed to (U,FP)3O8 after prolonged exposure to air at 950–1000°C. This suggests a marked widening of the (U,FP)4O9-phase field when the amount of substituted uranium atoms exceeds values of about 8%.