A simple and sensitive assay for eflornithine quantification in rat brain using pre-column derivatization and UPLC-MS/MS detection

Micellar sensitized Resonance Rayleigh Scattering and spectrofluorometric methods based on isoindole formation for determination of Eflornithine in cream and biological samples

α-Difluoromethylornithine or Eflornithine is an FDA-approved drug used for the treatment of Sleeping Sickness (as vials dosage form) and also used for diminishing the unwanted excess facial hair in the hirsutism (as creams dosage form). The proposed work is based on the condensation interaction between the amino moiety of Eflornithine and O-phthalaldehyde/2-mercaptoethanol to form a highly fluorescent isoindole derivative. The fluorescence and the Resonance Rayleigh Scattering (RRS) intensities of the reaction product were greatly augmented upon the addition of hexadecyl-trimethyl ammonium bromide by 153% and 250%, respectively. After optimization of the reaction conditions, the formed isoindole derivative was measured fluorometrically at λ_emission= 429 nm after λ_excitation= 337 nm. Moreover, the significant augmentation in the RRS intensity of the formed product was measured at λ_max= 422 nm. In regards to accuracy, sensitivity, robustness and precision, the proposed methods were validated according to ICH guidelines. Furthermore, the proposed methods were successfully applied for the assay of Eflornithine in various commercial brands of the pharmaceutical cream samples with good recovery. In addition to the current fluorometric method was confirmed to be effective in the assaying of Eflornithine in spiked plasma and urine specimens with good recovery.

Application of Hantzsch reaction for sensitive determination of eflornithine in cream, plasma and urine samples

Eflornithine (EFN) is an anti-Trypanosoma brucei agent for the medication of sleeping sickness and widely distributed for the treatment of hirsutism (unwanted facial hair in women). The presented work demonstrates a comprehensive analytical approach for the spectrofluorometric determination of EFN in commercial cream samples and various biological samples. The proposed method is based on the formation of a highly yellow-green fluorescence dihydropyridine derivative after the interaction between EFN and acetylacetone/formaldehyde reagent in a slightly acidic medium. Furthermore, the optimal variables such as reagent volumes, pH of the medium, heating time, buffer volume, heating temperature and diluting solvent were carefully selected to achieve the maximum fluorescence activity. The fluorescence activity for the formed derivative was measured at λ emission = 477 nm after λ excitation = 418 nm. Concerning linearity, accuracy, sensitivity, precision and robustness, the presented method was validated and verified according to ICH guidelines. Moreover, the proposed work offered a selective determination for EFN in various brands of pharmaceutical cream without any interference from excipients. Eventually, the current approach was assured to be successful in the estimation of EFN in urine and plasma samples with acceptable recovery results.

Utility of 4-chloro-7-nitrobenzofurazan for spectrofluorimetric and spectrophotometric determinations of the anti-hirsutism agent (α-difluoromethylornithine) in pharmaceutical cream samples

α-Difluoromethylornithine is an effective medication for the treatment of African Trypanosomiasis and widely distributed for the treatment of hirsutism. This work provides an adequate analytical protocol for the spectrophotometric and the spectrofluorimetric determination of α-difluoromethylornithine through its interaction with 4-chloro-7-nitrobenzofurazan (NBD-chloride) reagent. After optimization of the reaction conditions (NBD-chloride volume, buffer volume, the best diluting solvent, heating time and temperature and pH of the medium) the reaction product was measured spectrophotometrically at λ_max = 478 nm and spectrofluorimetrically at λ_emission = 540 nm after λ_excitation = 475 nm. The proposed methods were linear over the ranges 5-30 μg ml^-1 and 0.4-2 μg ml^-1 for the spectrophotometric method and the spectrofluorimetric method, respectively. Moreover, the proposed work offers an adequate sensitive and selective determination for α-difluoromethylornithine where the detection limits were 0.90 μg ml^-1 and 0.071 μg ml^-1 for the spectrophotometric method and the spectrofluorimetric method, respectively. Furthermore, both methods were successfully applied for the quantification of α-difluoromethylornithine in the pharmaceutical cream samples with acceptable recovery results.

Chiral Chromatographic Isolation on Milligram Scale of the Human African Trypanosomiasis Treatment d- and l-Eflornithine

Eflornithine is a recommended treatment against the otherwise fatal parasitic disease late stage human African trypanosomiasis (HAT), also known as Gambian sleeping sickness. It is administered repeatedly as a racemic mixture intravenously (IV) together with oral nifurtimox. Racemic eflornithine has been investigated in clinical trials for oral dosing. However, due to low systemic exposures at a maximum tolerated oral dose, the drug is continued to be administered IV. The eflornithine enantiomers, d- and l-eflornithine, have different affinities to the target enzyme ornithine decarboxylase, suggesting that the pharmacodynamics of the enantiomers may differ. The aim of this study was to develop a method for isolation of d- and l-eflornithine from a racemic mixture. Several chiral stationary phases (CSPs) were evaluated for enantioselectivity using supercritical fluid chromatography (SFC) or high-performance liquid chromatography (HPLC). None of the tested CSPs rendered separation of the enantiomers in SFC mode. Separation of the enantiomers with SFC on the CSP Chiralpak IG was only achieved on an analytical scale after derivatization with ortho-phthalaldehyde (OPA). This was the first reported enantioselective SFC method for an eflornithine derivate. However, due to poor stability, the eflornithine-OPA derivates degraded and no chemically pure enantiomers were obtained. The CSP that showed enantioselectivity in HPLC mode was Chirobiotic R, which resulted in a successful isolation on a semipreparative milligram scale. The isolated eflornithine enantiomers will be tested in nonclinical in vitro and in vivo studies to support and assess the feasibility of a future clinical program with an oral HAT treatment.