Capillary gas chromatographic determination of vincamine in plasma

Analysis of Two Mixtures Containing Racetams in Their Pharmaceuticals Using Simple Spectrophotometric Methodologies

BACKGROUND

Green spectrophotometric methods were developed and validated for determination of some CNS active drugs as antiepileptics and brain stimulants.

OBJECTIVE

Piracetam (PIR), Levetiracetam (LEV) and Brivaracetam (BRV) were assayed as a ternary mixture using double divisor-ratio spectra derivative (DDRSD) (method I). One more binary co-formulated mixture of Piracetam (PIR) and Vincamine (VIN) was assayed using difference spectrophotometric procedures (method II).

METHOD

Method I was applied to determine PIR at 302 nm in the first derivative of the ratio spectra in the selected spectral region. The content of LEV was determined by measuring the spectra at 215 nm in the first derivative of the ratio spectra in the selected spectral region. The concentration of BRV was estimated by measuring the first derivative of the ratio spectra in the chosen spectral region and detecting the signals at 229.7 nm. The application of method (II) procedures resulted in measuring the absorbance of PIR at 220 nm which is the zero crossing point on the difference spectra of VIN in 0.1 M NaOH vs. 0.1 M HCl. Similarly, the absorbance of VIN was measured at 245.0 nm, which is the zero crossing point on the difference spectra of PIR.

RESULTS

The suggested methods were fully validated adopting ICH guidelines. The linearity ranged from 10-100 µg/mL for the three racetams and from 2-20 for VIN. The recovery percentages were ranged from 98.72 % to 101.8 % for method I and from 98.13 % to 101.06 % for method II. Moreover, the proposed methods were proved environmentally benign using the most recent assessment tool named AGREE.

CONCLUSION

Both procedures were successfully applied for the determination of each drug in bulk powder, checked using laboratory prepared mixtures, and directly applied on commercially available pharmaceutical products without interference. The obtained results revealed a good agreement with those obtained by the reported methods.

Application of π acceptors to the spectrophotometric and spectrofluorimetric determination of vincamine and naftidrofuryl oxalate in their pharmaceutical preparations

Three different spectrophotometric and two spectrofluorimetric methods have been developed and validated for the determination of vincamine (VN) and naftidrofuryl oxalate (NF) in tablets. The spectrophotometric methods depend on charge transfer complex formation between each of VN and NF with 7,7,8,8-tetracyano-quinodimethane (TCNQ), 2,6-dichloroquinone-4-chloroimide (DCQ) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) at 843, 580 and 588 nm, respectively. The spectrofluorimetric methods are based on the formation of charge transfer complex between each of the two drugs and TCNQ, with measurement of the fluorophore formed at 312/375 and 284/612 nm, respectively, or with DDQ at 400/475 and 284/396 nm, respectively. In the spectrophotometric measurements, Beer's law was obeyed at concentration ranges of 1.5-16, 10-180 and 12-140 μg/ml for VN with TCNQ, DCQ, and DDQ, respectively. For NF, the corresponding concentrations were 2-28, 5-75 and 25-150 μg/ml with TCNQ, DCQ, and DDQ, respectively. In the spectrofluorimetric measurements, the ranges for VN were 0.05-0.9 and 0.3-4 μg/ml with TCNQ and DDQ, respectively, whereas for NF the ranges were 0.05-0.85 and 0.5-8 μg/ml with TCNQ and DDQ, respectively. The different experimental parameters affecting the development and stability of the formed color or fluorophore were studied and optimized and the molar ratios of the complexes were calculated. The proposed methods were validated according to ICH guidelines and were successfully applied for the determination of VN and NF in their tablet dosage forms.

Measurement and pharmacokinetics of vincamine in rat blood and brain using microdialysis

Vincamine is an alkaloid compound derived from the Vinca minor plant. Since little is known concerning its pharmacokinetics and appropriate analytical method, this study focuses on its pharmacokinetics as well the possible roles of the multidrug transporter P-glycoprotein on its distribution and disposition. We develop a rapid and sensitive method using a microdialysis coupled with liquid chromatography for the concurrent determination of unbound vincamine in rat blood and brain. Microdialysis probes were simultaneously inserted into the jugular vein toward heart and brain hippocampus of male Sprague-Dawley rats for sampling in biological fluids following the administration of vincamine (10 and 30 mg/kg) through the femoral vein. Samples were eluted with a mobile phase containing methanol-1% diethylamine (pH 7.15) in water (75:25, v/v) and the flow rate of the mobile phase was 0.7 ml/min. Pharmacokinetic parameters of vincamine were derived using compartmental model. The decline of protein-unbound vincamine in the hippocampus and blood suggested that there was rapid exchange and equilibration between the peripheral compartment and the central nervous system. In the presence of cyclosporine, unbound vincamine levels in both blood and brain were significantly increased.

Stability-indicating methods for determination of vincamine in presence of its degradation product

Three different stability indicating assay methods are developed and validated for determination of vincamine in the presence of its degradation product (vincaminic acid). The first method is based on the derivative ratio zero crossing spectrophotometric technique using 0.1 N hydrochloric acid as a solvent. In the second method, measurements are based on spectro-densitometric technique using high performance thin-layer chromatography (HPTLC) plates with a developing system consisting of methanol-chloroform-ethyl acetate (2:1:1, v/v/v). The third method depends on high-performance liquid chromatography (HPLC). Separation of vincamine from vincaminic acid using Lichrocart RP-18 column (250 mm x 4.6 mm i.d.) with a mobile phase consisting of acetonitrile-ammonium carbonate (0.01 M) (7:3, v/v) is achieved. The methods showed high sensitivity with good linearity over the concentration ranges of 12 to 48 microg ml-1, 3 to 17 microg/spot, and 2 to 20 microg ml-1 for derivative spectrophotometry, spectro-densitometry and HPLC methods, respectively. The developed methods were successfully applied to the analysis of pharmaceutical formulations containing vincamine with excellent recoveries.

Ion-molecule reactions of oxygenated chemical ionization reagents with vincamine

The ion-molecule reactions of ions from acetone, dimethyl ether, 2-methoxyethanol, and vinyl methyl ether with vincamine were investigated. Reactions with dimethyl ether result in [M+13](+) and [M+45](+) products, reactions with 2-methoxyethanol produce [M+13](+) and [M+89](+) ions, and reactions with acetone or vinyl methyl ether ions generate predominantly [M+43](+) ions. Collision-activated dissociation and deuterium labeling experiments allowed speculation about the product structures and mechanisms of dissociation. The methylene substitution process was shown to occur at the hydroxyl oxygen and the phenyl ring of vincamine for dimethyl ether reactions, but the methylene substitution process was not favored at the hydroxyl oxygen for the 2-methoxyethanol reactions, instead favored at the 12 phenyl position. The reaction site is likely different for the 2-methoxyethanol ion due to its capability for secondary hydrogen-bonding interactions. For the [M+45](+) and [M+89](+) ions, evidence suggests that charge-remote fragmentation processes occur from these products. In general, the use of dimethyl ether ions or 2-methoxyethanol ions for ionmolecule reactions prove highly diagnostic for the characterization of vincamine; both molecular weight and structural information are obtained. Limits of detection for vincamine with dimethyl ether chemical ionization via this technique on a benchtop ion trap gas chromatography-tandem mass spectrometer are in the upper parts per trillion range.

Determination of vincamine in human plasma by high-performance liquid chromatography with ultraviolet detection

A simple and rapid high-performance liquid chromatographic method was developed for the determination of vincamine in human plasma. Plasma samples were buffered at pH 9 and after extraction with tert.-butyl methyl ether back-extracted into 0.017 M orthophosphoric acid. Propranolol was used as the internal standard. An aliquot was injected on to a high-performance liquid chromatographic system using a C18 reversed-phase column and an acetonitrile-phosphate buffer containing triethylamine (30:70) as mobile phase. Detection was performed with an ultraviolet detector at 273 nm. The method had good accuracy and precision and the detection limit (0.3 ng/ml with a signal-to-noise ratio of 3:1) allowed the assessment of vincamine concentrations in plasma in pharmacokinetic studies on healthy human volunteers.