Improved determination of 5-fluorouracil and its prodrug tegafur in pharmaceuticals by large-volume sample stacking in CE

A simple and efficient sequential electrokinetic and hydrodynamic injections in micellar electrokinetic chromatography method for quantification of anticancer drug 5-fluorouracil and its metabolite in human plasma

A simple and sensitive preconcentration strategy using sequential electrokinetic and hydrodynamic injection modes in micellar electrokinetic chromatography with diode array detection was developed and applied for the separation and determination of anticancer agent, 5-fluorouracil and its metabolite, 5-fluoro-2'-deoxyuridine, in human plasma. Sequential injection modes with increased analyte loading capacity using the anionic pseudo-stationary phase facilitated collection of the dispersed neutral and charged analytes into narrow zones and improved sensitivity. Several important parameters affecting sample enrichment performance were evaluated and optimized in this study. Under the optimized experimental conditions, 614- and 643-fold and 782- and 803-fold sensitivity improvement were obtained for 5-fluorouracil and its metabolite when compared with normal hydrodynamic and electrokinetic injection, respectively. The method has good linearity (1-1,000 ng/ml) with acceptable coefficient of determination (r²  > 0.993), low limits of detection (0.11-0.14 ng/ml) and satisfactory analyte relative recovery (97.4-99.7%) with relative standard deviations of 4.6-9.3% (n = 6). Validation results as well as the application to analysis of human plasma samples from cancer patients demonstrate the applicability of the proposed method to clinical studies.

Antineoplastic drugs and their analysis: a state of the art review

We provide an overview of the analytical methods available for the quantification of antineoplastic drugs in pharmaceutical formulations, biological and environmental samples.

Identification of metabolites of the novel anti-tumor drug candidate MDH-7 in rat urine by liquid chromatography coupled with triple quadrupole linear ion trap mass spectrometry

RATIONALE

Our previous preliminary pharmacokinetic study demonstrated that the novel double pyrimidine tricyclic nucleoside MDH-7 in rats had a very short half-life (<30 min) after oral administration. As a result, the in vivo metabolic profile of MDH-7 should be investigated during early stages of drug development to better select drug candidates.

METHODS

In this study, a rapid method was developed to identify the metabolites of MDH-7 in rat urine by means of ultra-performance liquid chromatography (UPLC) coupled with electrospray ionization mass spectrometry (ESI-MS) using a triple quadrupole linear ion trap instrument. MDH-7 and its metabolites were detected and characterized by the combined use of the multiple reaction monitoring-information-dependent acquisition-enhanced product ion (MRM-IDA-EPI) mode and the precursor scan information-dependent acquisition-enhanced product ion (PREC-IDA-EPI) mode.

RESULTS

Ten novel metabolites of MDH-7 were identified and characterized in rat urine by LC/ESI-MS and collision-induced dissociation tandem mass spectrometry (CID-MS/MS) analyses. M1 was identified as 5-fluoro-N(4) -[(pentyloxy)carbonyl]cytosine; M2 and M3 were formed by hydroxylation products of M1. Metabolites M4-M10 were formed by a series of degradation reactions such as: deacetylation, hydroxylation, loss of the defluorocytosine base, oxidative-deamination, loss of the defluorouracil base, N-dealkylation and amide hydrolysis.

CONCLUSIONS

Based on the profiles of the metabolites, possible metabolic pathways of MDH-7 in rats were proposed for the first time. This study provides new and available information on the metabolism of MDH-7 which is very useful to further understand its in vivo metabolic fate. Copyright © 2016 John Wiley & Sons, Ltd.

Large-volume sample stacking with polarity switching for monitoring of nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) reactions by capillary electrophoresis

Nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) is a membrane glycoprotein involved in the hydrolysis of extracellular nucleotides. Its main substrate is ATP yielding AMP and pyrophosphate. NPP1 has been proposed as a novel drug target, for diabetes type 2 and the treatment of calcium pyrophosphate dihydrate deposition disease leading to inflammatory arthritis. The monitoring of NPP1 reactions is difficult because its velocity is very slow requiring highly sensitive analytical procedures. In this study, a method of large-volume sample stacking with polarity switching was developed, and separations were optimized. Large sample volumes were loaded by hydrodynamic injection (5 psi, 13 s) followed by removal of a large plug of sample matrix from the capillary using polarity switching (-10 kV). The stacked analytes were subsequently separated in phosphate buffer (100 mM, pH 9.2) at 20 kV. The validated method was found to be linear (R(2) = 0.9927) in the concentration range of 0.05-50 μM of AMP, with high accuracy and precision. The determined LOD and LOQ of AMP were 18 nM and 60 nM, respectively. Compared to a previously reported CE procedure using sweeping technique, a fivefold improvement of sensitivity was achieved. Moreover, the new technique was faster, and reproducibility of migration times was improved (RSD value = 1.2%). Importantly, adenine nucleotide analogs and derivatives tested as NPP1 inhibitors could be completely separated from the substrate ATP and the enzymatic product AMP. The method was applied to NPP1 inhibition assays investigating nucleotide-derived inhibitors in the presence of ATP.

Molecularly imprinted polymer for recognition of 5-fluorouracil by RNA-type nucleobase pairing

A 6-aminopurine (adenine) derivative of bis(2,2'-bithienyl)methane, vis., 4-[2-(6-amino-9H-purin-9-yl)ethoxy]phenyl-4-[bis(2,2'-bithienyl)methane] or Ade-BTM, was designed and synthesized for recognition of 5-fluorouracil (FU), an antitumor chemotherapy agent, by RNA-type (nucleobase pairing)-driven molecular imprinting. The prepolymerization complex stoichiometry involved one FU molecule and two molecules of the Ade-BTM functional monomer. Molecular structure of this complex was thermodynamically optimized via density functional theory at the B3LYP/3-21G* level. The stability constant of the FU-Ade-BTM complex of 1:2 stoichiometry was K = 2.17(±0.07) × 10(7) M(-2), as determined by titration with quenching of fluorescence of the bis(2,2'-bithienyl)methane moiety of Ade-BTM by the FU titrant, in benzonitrile, at 352 nm excitation. Next, (5-fluorouracil)-templated molecularly imprinted polymer (MIP-FU) films were deposited on indium-tin oxide (ITO) or Au film-coated glass slides, Pt disk electrodes, or 10-MHz quartz crystal resonators by potentiodynamic electropolymerization from solution of FU, Ade-BTM, and tris([2,2'-bithiophen]-5-yl)methane (TTM) cross-linking monomer at FU:Ade-BTM:TTM = 1:2:3 mol ratio. Then UV-visible and Fourier transform infrared (FT-IR) spectra of the MIP-FU films were recorded to confirm the FU template presence in the MIP-FU film and its subsequent release by extraction with methanol from this film. For determination of the stability constant of the complex of the MIP cavity and FU, piezoelectric microgravimetry (PM) under both batch- and flow-injection analysis conditions was used. For sensing application, three different transduction platforms [differential pulse voltammetry (DPV), capacitive impedimetry (CI), and PM] were integrated with the MIP-FU recognition unit. The limit of detection (LOD) was 56 nM, 75 nM, and 0.26 mM, for these chemosensors, respectively, indicating suitability of the former two for FU determination in blood plasma or serum (~500 nM). Moreover, the CI chemosensor was appreciably more sensitive to FU than to their common interferences.

Analysis of anticancer drugs: a review

In the last decades, the number of patients receiving chemotherapy has considerably increased. Given the toxicity of cytotoxic agents to humans (not only for patients but also for healthcare professionals), the development of reliable analytical methods to analyse these compounds became necessary. From the discovery of new substances to patient administration, all pharmaceutical fields are concerned with the analysis of cytotoxic drugs. In this review, the use of methods to analyse cytotoxic agents in various matrices, such as pharmaceutical formulations and biological and environmental samples, is discussed. Thus, an overview of reported analytical methods for the determination of the most commonly used anticancer drugs is given.

High-sensitivity capillary electrophoresis method for monitoring purine nucleoside phosphorylase and adenosine deaminase reactions by a reversed electrode polarity switching mode

A simple, efficient, and highly sensitive in-line CE method was developed for the characterization and for inhibition studies of the nucleoside-metabolizing enzymes purine nucleoside phosphorylase (PNP) and adenosine deaminase (ADA) present in membrane preparations of human 1539 melanoma cells. After filling the running buffer (50 mM borate buffer, 100 mM SDS, pH 9.10) into a fused-silica capillary (50 cm effective length × 75 μm), a large sample volume was loaded by hydrodynamic injection (5 psi, 36 s), followed by the removal of the large plug of sample matrix from the capillary using polarity switching (-20 kV). The current was monitored and the polarity was reversed when 95% of the current had been recovered. The separation of the neutral analytes (nucleosides and nucleobases) was performed by applying a voltage of 15 kV. An about 10-fold improvement of sensitivity for the five investigated analytes (adenosine, inosine, adenine, hypoxanthine, xanthine) was achieved by large-volume stacking with polarity switching when compared with CE without stacking. For inosine and adenine detection limits as low as 60 nM were achieved. To the best of our knowledge, this represents the highest sensitivity for nucleoside and nucleobase analysis using CE with UV detection reported so far. The Michaelis-Menten constants (K(m)) for PNP and ADA and the inhibition constants (K(i)) for standard inhibitors determined with the new method were consistent with literature data.

Contemporary sample stacking in CE

Sample stacking techniques remain an important tool for enhancement of the selectivity and sensitivity of analyses in contemporary CZE. This contribution reviews new knowledge on this topic published since 2006. It is organized according to the operational principles used, which include concentration adjustment, application of a pH step, MEKC and sweeping, and transient ITP. Techniques combining several of these principles and comparative studies are also included.

SPE and large-volume sample stacking in MEKC for determination of doxycycline in biological fluids: comparison of direct injection to SPE-MEKC

A novel and simple method has been developed for the determination of doxycycline (DOX) in biological fluids. The method is based on SPE, large-volume sample stacking (LVSS) and MEKC with UV-DAD detection. Six SPE cartridges have been used in investigation for sample clean up and pre-concentration (Supelco LC-8, LC-18, LC-SCX, and LC-WCX, as well as Strata-X and X-C). DOX was determined on a 56 cm (effective length 50 cm) x 50 microm id fused-silica capillary. The BGE was 20 mM borate buffer, pH 9.3, containing 80 mM SDS and 7.5% v/v of methanol (30 sx50 mbar), and the temperature and voltage were 25 degrees C and 30 kV, respectively. The analytical wavelength was set at 210 nm. Under optimized conditions it is possible to determine DOX in human serum, urine, semen, tears and saliva with recovery of 97.5% (RSD 2.5%). The method was shown to be sensitive (LOD is 1 microg/L) and precise (intra-day RSD 0.2 and 2.4%; inter-days 0.4 and 3.5% for migration time and peak area, respectively). Results for developed SPE-LVSS-MEKC were compared with LVSS-MEKC method with direct sample injection. The new LVSS-MEKC method is presented as a useful technique for rapid determination without extraction procedure of DOX in human urine and serum, using 80 mM of SDS, 10% v/v of methanol and 40 mM borate buffer (pH 9.3; 30 s x 50 mbar; 25 degrees C; 30 kV; 350 nm), but not for the other biological fluids, according to lower sensitivity of the method and because of the sample composition.