Gas chromatography-mass spectrometry identification of a novel N3-methylated metabolite of 5'-deoxy-5-fluorouridine in plasma of cancer patients undergoing chemotherapy

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.

Metabolite Profiling in Anticancer Drug Development: A Systematic Review

Drug metabolism is one of the most important pharmacokinetic processes and plays an important role during the stage of drug development. The metabolite profile investigation is important as the metabolites generated could be beneficial for therapy or leading to serious toxicity. This systematic review aims to summarize the research articles relating to the metabolite profile investigation of conventional drugs and herb-derived compounds for cancer chemotherapy, to examine factors influencing metabolite profiling of these drugs/compounds, and to determine the relationship between therapeutic efficacy and toxicity of their metabolites. The literature search was performed through PubMed and ScienceDirect databases up to January 2019. Out of 830 published articles, 78 articles were included in the analysis based on pre-defined inclusion and exclusion criteria. Both phase I and II enzymes metabolize the anticancer agents/herb-derived compounds . The major phase I reactions include oxidation/hydroxylation and hydrolysis, while the major phase II reactions are glucuronidation, methylation, and sulfation. Four main factors were found to influence metabolite formation, including species, gender, and route and dose of drug administration. Some metabolites were identified as active or toxic metabolites. This information is critical for cancer chemotherapy and anticancer drug development.

Analysis of modified nucleosides in the urine of patients with malignant cancer by liquid chromatography/electrospray ionization mass spectrometry

As modified nucleosides reflect altered tRNA turnover which seems to be impaired in the body of cancer patients, they have been evaluated as potential tumor markers. High-performance liquid chromatography/electrosprary ionization quadrupole time-of-flight mass spectrometry (HPLC/ESI-Q-TOFMS) was used to identify nucleosides purified from urine in positive ionization mode. Potential nucleosides were assessed by their evident UV absorbance in HPLC and then further examined by mass spectrometric techniques. In this manner, 21 nucleosides were detected in the urine of a patient with lymphoid cancer including three modified nucleosides 5'-dehydro-2-deoxyinosine, N1,N2,N7-trimethylguanosine and N1-methyl-N2-ethylguanosine, which had never been reported previously.

Determination of N3-methyl-5'-deoxy-5-fluorouridine, a novel metabolite of doxifluridine, in body fluids by high performance liquid chromatography

A high performance liquid chromatography method for the determination of N3-methyl-5'-deoxy-5-fluorouridine, a possible metabolic product of the anticancer pro-drug 5'-deoxy-5-fluorouridine, in human serum and urine is described. Sample treatment involved addition of internal standard (5-bromouracil) and protein precipitation with ammonium sulphate (serum samples) followed by liquid-liquid extraction with ethyl acetate-isopropanol (90:10, v/v). The average recovery at 0.5 mg ml-1 level was (80 +/- 4%). A linear response extending over two decades of concentration was observed. Detection limits of 50 and 100 ng ml-1 were obtained in serum and urine, respectively.

In vitro toxicity of N3-methyl-5'-deoxy-5-fluorouridine, a novel metabolite of doxifluridine: a bioanalytical investigation

The cytotoxicity of N3-methyl-5'-deoxy-5-fluorouridine (N3-Me-5'-dFUR), a novel metabolite of the anticancer pro-drug 5'-deoxy-5-fluorouridine (5'-dFUR), has been evaluated by in vitro experiments with cultures of different cancer cell lines. The new metabolic product was found to be non-toxic in all the cell growth experiments performed. The absence of cytotoxicity could be explained by the observation that the metabolite was not recognized as a substrate by thymidine phosphorilase, the enzyme responsible for 5-fluorouracil (5-FU) release from doxifluridine, as ascertained by high-performance liquid chromatography/ultraviolet (HPLC-UV) analysis of the incubation mixture. The biomethylation process leading to N3-Me-5'-dFUR could be considered as a possible detoxification pathway, altering the drug bioavailability, in competition with 5'-dFUR cleavage to the active 5-FU.