Wanhui Liu

Sensitive liquid chromatographic assay for the simultaneous determination of 5-fluorouracil and its prodrug, tegafur, in beagle dog plasma.

A high-performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of 5-fluorouracil (5-FU) and its prodrug, tegafur (TF), in dog plasma. 5-FU, the internal standard, 5-bromouracil, and TF were separated on a C18 Spherisorb ODS2 column using isocratic elution with retention times of 4.4, 8.0 and 21.2 min, respectively. Detection by UV absorption at 260 nm gave a limit of quantitation of 4 microg/l for 5-FU in plasma. Calibration curves for 5-FU and TF were linear over the ranges of 4-160 microg/l and 0.48-19.2 mg/l, respectively. Intra- and inter-day precision over these concentration ranges were <10.9 and <13.6% for 5-FU and TF, respectively, with good accuracy for both compounds. The method was successfully applied to define plasma concentration-time curves of TF and 5-FU in dogs administered a single oral dose containing TF (100 mg) and uracil (224 mg).

Synthesis of a bi-functional dendrimer-based nanovehicle co-modified with RGDyC and TAT peptides for neovascular targeting and penetration

The dual-ligand dendritic polyamidoamine-(polyethylene glycol)n-cyclic RGDyC peptide-(TAT peptide) (PPnR(T)) with various supplied molar ratios of polyethylene glycol (PEG) to polyamidoamine (PAMAM) (n=5, 15, 30) were designed as drug-carriers for the treatment of neovascular diseases; their targeting and penetrating effects were subsequently evaluated. (1)H NMR demonstrated PPnR(T) was successfully synthesized. Compared with the unmodified PAMAM, in vitro cytotoxicity of PPnR(T) to αvβ3 negative cells (αvβ3-) was significantly reduced, whereas the lethality to pathologic neovascular endothelial cells (αvβ3+) was efficiently increased compared to PPn. Compared to PP5R(T) and PP15R(T), PP30R(T) exhibited the most selective and efficient cellular uptake by human umbilical vein endothelial cells (HUVECs, αvβ3+). Membrane interaction study indicated the cellular uptake process of PP30R(T) of HUVECs mainly involved specific RGD-αvβ3 recognition as well as electrostatic interactions. Intracellular localization results confirmed PP30R(T) was distributed in the cytoplasm in HUVECs. 3D tumor spheroids penetration studies demonstrated that PP30R(T) penetrated the A549 cells to reach the depths of the avascular tumor spheroids. In vivo imaging further demonstrated that PP30R(T) achieved profoundly improved distribution in tumor tissues where angiogenesis existed. Therefore, the bi-functional dendrimer PP30R(T) displayed great potential as a nano-carrier for targeted drug delivery both in vitro and in vivo, and had broad prospects as nanocarriers for the targeted treatment of neovascular diseases.

Pharmacokinetics and bioavailability of cimicifugosides after oral administration of Cimicifuga foetida L. extract to rats

ETHNOPHARMACOLOGICAL RELEVANCEnCimicifuga foetida L., a traditional Chinese medicine, has been used as an anti-inflammatory, antipyretic and analgesic remedy. The primary active constituents are believed to be present in the triterpene glycoside fraction.nnnMATERIALS AND METHODSnTo develop an LC-MS/MS assay for four major cimicifugosides [cimicifugoside H-1 (Cim A), 23-epi-26-deoxyactein (Cim B), cimigenolxyloside (Cim C) and 25-O-acetylcimigenoside (Cim D)] obtained from C. foetida L. and apply it to investigate their pharmacokinetic (PK) properties and bioavailabilities through oral administration of C. foetida L. extract (12.5, 25 and 50mg/kg) and single intravenous (i.v.) doses (5mg/kg) of the individual cimicifugosides in rat. PK parameters were estimated by non-compartmental analysis.nnnRESULTSnAll calibration curves showed excellent linear regressions (all r>0.995) within the range of tested concentrations. The intra- and inter-day variations were <15% in terms of RSD. The molar ratio of Cims A, B, C, and D in the extract was 20.7:1.4:2.9:1. PK parameters for Cims A, B, C, and D following oral administration of the extract were respectively: C(max) 4.05-17.69, 90.93-395.7, 407.1-1180 and 21.56-45.09pmol/mL; T(max) 0.46-1.28, 2.00-4.67, 14.67-19.67 and 8.08-14.27h; absolute oral bioavailability (F) 1.86-6.97%, 26.8-48.5%, 238-319% and 32.9-48%. PK parameters after i.v. administration of individual cimicifugosides were respectively: elimination half-life 1.1, 2.5, 5.7 and 4.2h; clearance 15.7, 0.48, 0.24 and 1.13mL/hkg.nnnCONCLUSIONSnSystemic exposure to Cims B, C and D following oral administration of the extract was significantly greater than to Cim A despite the predominance of Cim A in the extract. Significantly different clearance and interconversion from Cim A to Cim C probably accounts for the different exposure to the four cimicifugosides.

High-performance liquid chromatography spectrometric analysis of tripterin in rat plasma

A quick, precise and reliable HPLC method has been developed to determine tripterin in rat plasma. After liquid-liquid extraction, the analytes was analyzed on a Discovery ODS C(18) column (5microm, 4.6mmx250mm) with an isocratic elution consisting of methanol-water-phosphoric acid (87:13:0.2, v/v/v). Ultraviolet detection was at 425nm. Using trioxymethylanthraquinone as an internal standard, the assay was linear over the concentration range of 0.025-1.60microg/mL (r(2)=0.9988). The extraction recovery of tripterin in rat plasma was more than 62%. The intra- and inter-day precision was less than 13% (CV). This validated method was successfully applied to the pharmacokinetics of tripterin in rats.

Effect of palmitic acid on the characteristics and release profiles of rotigotine-loaded microspheres

Abstract Background: The initial burst release is a major obstacle to the development of microsphere-formulated drug products. Purpose: To investigate the influence of palmitic acid on the characteristics and release profiles of rotigotine-loaded poly(d,l-lactide-co-glycolide) microspheres. Materials and methods: Rotigotine-loaded microspheres (RMS) were prepared using the oil-in-water emulsion solvent evaporation technique. The in vitro characteristics of the RMS were evaluated with scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and a particle size analyzer. The in vitro drug release and in vivo pharmacokinetics of the RMS were investigated. Results and discussion: The SEM results showed that the addition of palmitic acid changed the surface morphology of the microspheres from smooth to dimpled and then to non-smooth as the palmitic acid content increased. DSC revealed the existence of molecularly dispersed forms of palmitic acid in the microspheres. The in vitro and in vivo release profiles indicated that the addition of 5% and 8% palmitic acid significantly decreased the burst release of rotigotine from the microspheres, and the late-stage release was delayed as the palmitic acid content increased across the investigated range (5–15%). Conclusion: The addition of palmitic acid to the microspheres significantly affects the release profile of rotigotine from RMS.

Optimization, validation and application of an assay for the activity of HMG-CoA reductase in vitro by LC–MS/MS

A stable HMG-CoA reductase (HMGR) reaction in vitro was developed by a sensitive, selective and precise liquid chromatography–tandem mass spectrometry (LC–MS/MS) method. The optimized enzyme reaction condition contained 1.5 μg of HMGR, 20 nM of NADPH with 50 min of reaction time. The method was validated by several intra- and inter-day assays. The production transitions of m/z 147.0/59.1 and m/z 154.0/59.1 were used to detect and quantify mevalonolactone (MVAL) and MVAL-D7, respectively. The accuracy and precision of the method were evaluated over the concentration range of 0.005–1.000 μg/mL for MVAL and 0.010–0.500 μg/mL for lovastatin acid in three validation batch runs. The lower limit of quantitation was found to be 0.005 μg/mL for MVAL and 0.010 μg/mL for lovastatin acid. Intra-day and inter-day precision ranged from 0.95% to 2.39% and 2.26% to 3.38% for MVAL, 1.46% to 3.89% and 0.57% to 5.10% for lovastatin acid, respectively. The results showed that the active ingredients in Xuezhikang capsules were 12.2 and 14.5 mg/g, respectively. This assay method could be successfully applied to the quality control study of Xuezhikang capsule for the first time.

Development and validation of a sensitive LC-MS/MS assay for simultaneous quantitation of ranolazine and its three metabolites in human plasma.

A rapid, sensitive and reliable LC-MS/MS method was developed and validated for the simultaneous determination of ranolazine and its three metabolites, CVT-2514, CVT-2738, and CVT-4786, in human plasma. The plasma samples were prepared by protein precipitation. Chromatographic separation was achieved on a Gemini C(18) column (50 mm × 2.0 mm, 5 μm) using methanol: 5 mM ammonium acetate as the mobile phase with gradient elution. Mass detection was carried out by electrospray ionization in both positive and negative ion multiple reaction monitoring (MRM) modes. The calibration curves were linear over a concentration range of 4-2000 ng/mL for ranolazine, 4-1000 ng/mL for CVT-2514 and CVT-2738 and 8-1000 ng/mL for CVT-4786. The intra-day and inter-day accuracy and precision were within the acceptable limits of ±15% at all concentrations. The method was successfully applied for the simultaneous estimation of ranolazine and its three metabolites in human plasma from a clinical pharmacokinetics study.

Preparation and evaluation of injectable Rasagiline mesylate dual-controlled drug delivery system for the treatment of Parkinson’s disease

Abstract A microsphere–gel in situ forming implant (MS–Gel ISFI) dual-controlled drug delivery system was applied to a high water-soluble small-molecule compound Rasagiline mesylate (RM) for effective treatment of Parkinson’s disease. This injectable complex depot system combined an in situ phase transition gel with high drug-loading and encapsulation efficiency RM–MS prepared by a modified emulsion-phase separation method and optimized by Box–Behnken design. It was evaluated for in vitro drug release, in vivo pharmacokinetics, and in vivo pharmacodynamics. We found that the RM-MS-Gel ISFI system showed no initial burst release and had a long period of in vitro drug release (60u2009days). An in vivo pharmacokinetic study indicated a significant reduction (pu2009<u2009.01) in the initial high plasma drug concentration of the RM–MS–Gel ISFI system compared to that of the single RM–MS and RM–in situ gel systems after intramuscular injection to rats. A pharmacodynamic study demonstrated a significant reduction (pu2009<u2009.05) in 6-hydroxydopamine-induced contralateral rotation behavior and an effective improvement (pu2009<u2009.05) in dopamine levels in the striatum of the lesioned side after 28u2009days in animals treated with the RM–MS–Gel ISFI compared with that of animals treated with saline. MS-embedded in situ phase transition gel is superior for use as a biodegradable and injectable sustained drug delivery system with a low initial burst and long period of drug release for highly hydrophilic small molecule drugs.

Novel strategy using tryptic peptide immunoaffinity-based LC–MS/MS to quantify denosumab in monkey serum

AIMnDenosumab is a recombinant fully human IgG2 that has a high affinity and specificity for human RANKL. Commercially available RANKL labeled with an Fc fragment cannot be used to establish an indirect ELISA. To characterize denosumab pharmacokinetic a robust and accuracy method should be developed urgently.nnnRESULTSnIn this study, an immunoaffinity enrichment method coupled with LC-MS/MS was established. The LC-MS/MS method acquired a linear range from 0.1 to 30xa0μg/ml. The intra- and inter-run precision (CV%) was within 11.5 and 10.5%, respectively. More importantly, the LC-MS/MS pharmacokinetic data were consistent with ELISA.nnnCONCLUSIONnThis approach accelerated the quantification, reduced the costs and provided an alternative in case of lacking the special antigen to denosumab or a RANKL-biotinylated reagent.

Application of hot-melt extrusion technology for designing an elementary osmotic pump system combined with solid dispersion for a novel poorly water-soluble antidepressant

Abstract TP1 is a novel antidepressant with poor solubility. To reduce fluctuations in blood concentration and increase oral bioavailability, a controlled-release system was developed by combining a solid dispersion (SD) and an elementary osmotic pump (EOP). The study compared different methods of preparing SDs. Hot-melt extrusion (HME) exhibited clear advantages over the traditional melting technique. An in vitro release study demonstrated that HME-EOP tablets released TP1 in a zero-order manner over 12u2009h and the drug release was in dependent of the release medium and agitation speed, whereas release from molten-EOP tablets lasted only 8u2009h. In contrast to immediate-release tablets, the HME-EOP tablets exhibited less fluctuation in blood concentration and higher bioavailability in vivo. In summary, the osmotic pump system combined with an HME-based SD of TP1 presented controlled release in vitro, high bioavailability in vivo and a good in vivo–in vitro correlation.