Highly sensitive method for the determination of 5-fluorouracil in biological samples in the presence of 2'-deoxy-5-fluorouridine by gas chromatography-mass spectrometry

A Critical Review on Clinical Application of Separation Techniques for Selective Recognition of Uracil and 5-Fluorouracil

The most important objectives that are frequently found in bio-analytical chemistry involve applying tools to relevant medical/biological problems and refining these applications. Developing a reliable sample preparation step, for the medical and biological fields is another primary objective in analytical chemistry, in order to extract and isolate the analytes of interest from complex biological matrices. Since, main inborn errors of metabolism (IEM) diagnosable through uracil analysis and the therapeutic monitoring of toxic 5-fluoruracil (an important anti-cancerous drug) in dihydropyrimidine dehydrogenase deficient patients, require an ultra-sensitive, reproducible, selective, and accurate analytical techniques for their measurements. Therefore, keeping in view, the diagnostic value of uracil and 5-fluoruracil measurements, this article refines several analytical techniques involved in selective recognition and quantification of uracil and 5-fluoruracil from biological and pharmaceutical samples. The prospective study revealed that implementation of molecularly imprinted polymer as a solid-phase material for sample preparation and preconcentration of uracil and 5-fluoruracil had proven to be effective as it could obviates problems related to tedious separation techniques, owing to protein binding and drastic interferences, from the complex matrices in real samples such as blood plasma, serum samples.

A review of analytical methods for the determination of 5-fluorouracil in biological matrices

5-Fluorouracil (5-FU) is a cytostatic agent that has been widely used in the treatment of various solid tumours for more than 20 years, and is still considered to be among the most active antineoplastic agents in advanced colorectal cancer and malignancies of the head and neck. A large number of non-chromatographic and chromatographic methods for the quantitation of 5-FU, related prodrugs and their metabolites in biological matrices have been developed in the last 30 years to support preclinical and clinical studies. However, 5-FU monitoring has not been widely used, at least not in the USA, and certainly not outside the clinical research setting, given the absence of simple, fast and inexpensive testing methods for 5-FU monitoring. Recent developments with testing based on liquid chromatography-tandem mass spectrometry and a nanoparticle antibody-based immunoassay may facilitate routine monitoring of 5-FU in daily clinical practice. In this review the advantages and disadvantages of the bioanalytical methods developed and used for 5-FU, its metabolites and related prodrugs are discussed.

Determination of tegafur, 5-fluorouracil, gimeracil and oxonic acid in human plasma using liquid chromatography-tandem mass spectrometry

S-1 is an oral anticancer drug, which consists of tegafur (FT), gimeracil (CDHP) and potassium oxonate (Oxo) at a molar ratio of 1:0.4:1. Among these, tegafur is a prodrug, and is rapidly metabolized to the active drug, 5-fluorouracil (5-FU), in vivo. To evaluate the pharmacokinetics of S-1 in patients, LC-MS/MS methods were developed and validated for determination of FT, 5-FU, CDHP and Oxo in human plasma. FT, 5-FU and CDHP were extracted from plasma following protein precipitation, separated on a Synergi Hydro-RP column and simultaneously quantified by LC-MS/MS. The mobile phase consisted of methanol-water-ammonia-acetic acid (27:73:0.0018:0.018, v/v/v/v). The mass spectrometer was operated in negative mode using electrospray ionization. The calibration curves were linear in the range of 12.0-3000ng/mL for FT, and 2.00-500ng/mL for 5-FU and CDHP. The accuracy ranged from 93.1% to 110.7% and the precision ranged from 2.4% to 14.6% for each analyte. To determine Oxo in human plasma, an LC-MS/MS method employing pre-column derivatization was developed and validated. 4-Bromomethyl-7-methoxycoumarin was chosen as the derivatization reagent and [(13)C(2),(15)N(3)]-Oxo was used as the internal standard. The MS/MS detection was operated in positive mode using an APCI source. The calibration range was 2.00-150ng/mL. The accuracy and precision were within 95.9-99.1% and 4.4-10.0%, respectively. The validated methods were successfully applied to characterize the pharmacokinetic profiles of FT, 5-FU, CDHP and Oxo following oral administration of 60mg S-1 tablets to patients with solid gastrointestinal tract tumors.

Determination of 5-fluorouracil and its prodrug tegafur in plasma and tissue by high-performance liquid chromatography in a single injection: validation for application in clinical pharmacokinetic studies

Tegafur, a prodrug of 5-fluorouracil (5-FU), is an oral fluorouracil antitumor drug used for the management of adenocarcinomas. It has an efficacy similar to that of intravenous 5-FU, with potential advantages in terms of convenience and quality of life for the patient and cost-effectiveness as compared with intravenous chemotherapy. The authors developed a high-performance liquid chromatography (HPLC) assay for the determination of tissue or plasma tegafur and 5-FU concentration in a single step extraction and a single HPLC injection. The retention times of 5-FU and tegafur were 5 and 16.5 minutes, respectively, and the internal standard retention times were 11.5 and 17.5 minutes for 5-bromouracil (5-BU) and beta-hydroxyethyltheophylline, respectively. The limit of quantification was 0.0125 microg/mL for 5-FU and 0.05 microg/mL for tegafur. The assay had good recovery (96.5% +/- 9.45% and 97.5% +/- 7.89% for 5-FU in plasma and tissue, respectively, and 88.5% +/- 12.17% and 104.9% +/- 8.77% for tegafur in plasma and tissue, respectively). Precision was good: the within-day and between-day standard deviation of the mean (RSD) for 5-FU (0.0125-5 microg/mL) and tegafur (0.5-150 microg/mL) was always <8%. The authors conclude that the method described here is ideally suited for the therapeutic monitoring of 5-FU and tegafur.

RP-LC determination of 5-fluorouridine in nanoparticulate formulations

5-fluorouridine (5-FUrd) is an anticancerous drug with a number of side effects due to its high toxicity. One possibility to overcome these drawbacks may consist on the use of polymeric nanoparticles to increase the therapeutic index of this drug. The objective of this study was to develop an analytical high performance liquid chromatography (HPLC) method for the determination of (i) the 5-FUrd content in poly (methyl vinyl ether-co-maleic anhydride) nanoparticles, (ii) its release from these carriers and, its eventual degradation during preparation, storage or release in 5-fluorouracil (5-FU). The chromatography was performed on a reversed-phase encapped column (LiChrospher Select B C8) with a mobile phase of 0.05 M ammonium acetate (pH 6.5). Ganciclovir (GCV) was used as internal standard and the detection wavelength was 268 nm. The limits of quantification of 5-FUrd and 5-FU were 12 and 5 ng/ml, respectively. Similarly, precision did not exceed 7%. Under our experimental conditions, the maximal drug loading capacity of 5-FUrd was around 105 microg/mg nanoparticle and the drug was released in a biphasic way from these particles. In addition, no degradation of 5-FUrd to 5-FU during either the preparative process or the release studies was observed. In summary, this HPLC method is selective, sensitive, specific and reproducible for the quantification of 5-FUrd in polymeric nanoparticles and release mediums.

Hyphenated chromatographic methods for biomaterials

The improvement in hyphenated analytical techniques has significantly widened their applications to the analysis of biomaterials. In this article, we discuss recent advances in applications of hyphenated chromatographic techniques including capillary electrophoresis to the analyses of biological samples. As tools of separation, gas chromatography, high-performance liquid chromatography and capillary electrophoresis are considered with special emphasis on applications utilizing the hyphenation of these methods to mass spectrometry. Moreover, applications using other detection methods such as Fourier transform infrared spectroscopy hyphenated to gas chromatography and photodiode array detector combined with high-performance liquid chromatography or capillary electrophoresis are also discussed. Owing to their high sensitivity, luminescence-based detection systems such as laser-induced fluorescence and chemiluminescence are also included in this review.

Derivatization of 5-fluorouracil with 4-bromomethyl-7-methoxycoumarin for determination by liquid chromatography-mass spectrometry

A robust new analytical method has been developed for the determination of 5-fluorouracil (5-FU) in human plasma samples using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The method is based on a liquid-liquid extraction procedure, precolumn derivatization, reversed-phase HPLC separation, and detection using atmospheric pressure chemical ionization and selected reaction monitoring. The derivatization agent used was 4-bromomethyl-7-methoxycoumarin. The internal standard for the assay procedure was a stable isotope labeled analog of 5-FU. The lower limit of quantitation was 1.0 ng/mL using 500 microL aliquots of plasma. Sample throughput on the mass spectrometer was approximately 17 samples/h (3.5 min/sample). The method was fully validated. The recovery of 5-FU averaged 76.1%. The accuracy of the assay, assessed from quality control samples, ranged from 99.1% to 104.3% (% theoretical). The overall interassay precision (% RSD) was 2.7%, and the intraassay precision (% RSD) ranged from 1.5% to 3.9%. The derivatized samples were found to be stable under sample analysis conditions and during refrigerator storage. The method was specific for the determination of 5-FU.

Determination of S-1 (combined drug of tegafur, 5-chloro-2,4-dihydroxypyridine and potassium oxonate) and 5-fluorouracil in human plasma and urine using high-performance liquid chromatography and gas chromatography-negative ion chemical ionization mass spectrometry

A high-performance liquid chromatography (HPLC) and gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICI-MS) method was developed for the analysis of the combined antitumor drug S-1 (tegafur, 5-chloro-2,4-dihydroxypyridine and potassium oxonate) and active metabolite 5-fluorouracil in human plasma and urine. Tegafur was fractionated from biological fluids by extraction with dichloromethane and analyzed by HPLC. 5-Fluorouracil and 5-chloro-2,4-dihydroxypyridine were extracted with ethyl acetate from the residual layer after extraction of tegafur, and converted to pentafluorobenzyl (PFB) derivatives. Potassium oxonate was cleaned up with an anion-exchange column (Bond Elut NH2). The extracted potassium oxonate was degraded to 5-azauracil and converted to PFB derivatives. The PFB derivatives were analyzed by GC-NICI-MS. A stable isotope was employed as the internal standard in the GC-NICI-MS analysis. The limits of quantitation of tegafur, 5-fluorouracil, 5-chloro-2,4-dihydroxypyridine and potassium oxonate in plasma were 10, 1, 2 and 1 ng/ml, respectively. The reproducibility of the analytical method according to the statistical coefficients is approximately 10%. The accuracy of the method is good; that is, the relative error is < 10%. The methods were applied to pharmacokinetic studies of S-1 in patients.

Determination of 5-fluorouracil in human plasma by a simple and sensitive reversed-phase HPLC method

A simple and sensitive reversed-phase HPLC method with UV detection was developed and validated for the quantitation of 5-fluorouracil (5-FC) in human plasma. After acidification and salting out, 5-FU was extracted into ethyl acetate and back-extracted into a basic buffer. The extract was adjusted to neutral pH before being injected onto the HPLC column. 5-FU was separated from the matrix components on a YMC ODS-AQ column at 40 degrees C using an aqueous mobile phase of 10 mM potassium phosphate at pH 5.5. A linear gradient of 0-25% methanol wash eluted late peaks, maintained column performance, and increased column stability. The run time was 20 min. The linear range was 25-300 ng ml-1 (r2 > 0.999). The limit of quantitation was 25 ng ml-1, with a signal-to-noise ratio of 23:1. Interday precision and accuracy of quality control samples were 6.2-8.4% relative standard deviation and -0.1(-)+1.9% relative error.

Leukopenia-inducing effect of a combination of a new 5-fluorouracil (5-FU)-derived drug, BOF-A2 (emitefur), with other 5-FU-derived drugs or BV-araU (sorivudine) in rats

BOF-A2 (emitefur: 3-(3-[6-benzoyloxy-3-cyano-2-pyridyloxycarbonyl]benzoyl)-1-ethoxy- methyl-5- fluorouracil), a novel 5-FU (5-fluorouracil)-derived drug, was co-administered with other conventional 5-FU-derived drugs or BV-araU [sorivudine: 1-beta-D-arabinofuranosyl-(E)-5-(2-bromovinyluracil)] for 8 consecutive days to rats. BOF-A2 (6 or 8 mg/kg, p.o.) co-administered with other 5-FU-derived drugs elevated the plasma 5-FU concentration 3- to 23.3-fold and decreased the peripheral white blood cell (WBC). The percentage decreases of WBC by 5-FU (4 mg/kg, i.p.), UFT (16 mg/kg, p.o.), tegafur (FT; 16 mg/kg, p.o.), carmofur (HCFU; 15 mg/kg, p.o.), doxifluridine (5'-DFUR; 16 mg/kg, p.o.) and flucytosine (200 mg/kg, p.o.) were 25.7%, 31.9%, 70.3%, 32.0%, 58.6% and 30.0%, respectively, compared with each drug alone. On the other hand, these phenomena did not occur with BV-araU. These findings can be attributed to the fact that the inhibitory activity of CNDP (3-cyano-2,6-dihydroxypyridine) for 5-FU degradation (IC50: 6.3 x 10(-9) M) is potent and 6000 times greater than that of BVU [(E)-5-(2-bromovinyl) uracil], another inhibitor of 5-FU degradation.

Gas chromatographic-mass spectrometric method for routine monitoring of 5-fluorouracil in plasma of patients receiving low-level protracted infusions

A gas chromatographic-mass spectrometric (GC-MS) method is described which quantitates 5-fluorouracil (5-FU) plasma levels ranging from 0.5 to 50 ng/ml. The analysis uses two internal standards, 1,3-[15N2]-5-fluorouracil and 5-chlorouracil. Extraction and derivatization of the pyrimidine bases were accomplished in a single step using acetonitrile. Compounds were analyzed as their 1,3-dipentafluorobenzyl derivatives by electron-impact MS, and the GC-MS analysis was automated with respect to sample injection and data reduction. Stability of the analysis was demonstrated by continuous unattended analysis of 5-FU in human plasma for periods of up to three days with no deterioration of the quantitative results. The method is applicable to quantitating 5-FU plasma levels in patients receiving protracted infusions of the drug for colorectal cancer or other malignancies.