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.

Stability-Indicating TLC-Densitometric and HPLC Methods for the Simultaneous Determination of Piracetam and Vincamine in the Presence of Their Degradation Products.

Newly established TLC-densitometric and RP-HPLC methods were developed and validated for the simultaneous determination of Piracetam (PIR) and Vincamine (VINC) in their pharmaceutical formulation and in the presence of PIR and VINC degradation products, PD and VD, respectively. The proposed TLC-densitometric method is based on the separation and quantitation of the studied components using a developing system that consists of chloroform-methanol-glacial acetic acid-triethylamine (8 + 2 + 0.1 + 0.1, v/v/v/v) on TLC silica gel 60 F254 plates, followed by densitometric scanning at 230 nm. On the other hand, the developed RP-HPLC method is based on the separation of the studied components using an isocratic elution of 0.05 M KH2PO4 (containing 0.1% triethylamine adjusted to pH 3 with orthophosphoric acid)-methanol (95 + 5, v/v) on a C8 column at a flow rate of 1 mL/min with diode-array detection at 230 nm. The developed methods were validated according to International Conference on Harmonization guidelines and demonstrated good accuracy and precision. Moreover, the developed TLC-densitometric and RP-HPLC methods are suitable as stability-indicating assay methods for the simultaneous determination of PD and VD either in bulk powder or pharmaceutical formulation. The results were statistically compared with those obtained by the reported RP-HPLC method using t- and F-tests.

Determination of terpenoid indole alkaloids in hairy roots of Rhazya stricta (Apocynaceae) by GC-MS.

INTRODUCTION: Rhazya stricta Decne. (Apocynaceae) is a medicinal plant rich in terpenoid indole alkaloids (TIAs), some of which possess important pharmacological properties. The study material including transgenic hairy root cultures have been developed and their potential for alkaloid production are being investigated. OBJECTIVE: In this study, a comprehensive GC-MS method for qualitative and quantitative analysis of alkaloids from Rhazya hairy roots was developed. METHODS: The composition of alkaloids was determined by using GC-MS. In quantification, the ratio between alkaloid and internal standard was based on extracted ion from total ion current (TIC) analyses. RESULTS: The developed method was validated. An acceptable precision with RSD ≤ 8% over a linear range of 1 to 100 µg/mL was achieved. The accuracy of the method was within 94-107%. Analysis of hairy root extracts indicated the occurrence of a total of 20 TIAs. Six of them, pleiocarpamine, fluorocarpamine, vincamine, ajmalicine and two yohimbine isomers are reported here for the first time in Rhazya. Trimethylsilyl (TMS) derivatisation of the extracts resulted in the separation of two isomers for yohimbine and also for vallesiachotamine. Clearly improved chromatographic profiles of TMS-derivatives were observed for vincanine and for minor compounds vincamine and rhazine. CONCLUSION: The results show that the present GC-MS method is reliable and well applicable for studying the variation of indole alkaloids in Rhazya samples.

[Tissue culture of Vinca minor and determination of vincamine].

OBJECTIVE: To study tissue culture of Vinca minor and determine the content of vincamine. METHOD: Leaf blades, stalks, root segment of V. minor were used as explants to study the effect of 2, 4-D,6-BA,NAA on its callus induction and vincamine contents in the orthogonal design experiment. In the peak period of callus formation, vincamine content in callus of V. minor and sterile plants was determined by HPLC. The experimental data was statistically analyzed. RESULT: The content of 6-BA and NAA had no significant effect on its callus induction. But the content of 2, 4-D had significant effect on its callus induction. Within 20,40,60 d, the content of vincamine in sterile plant was (0.015 +/- 0.003)%, (0.097 +/- 0.001)% , (0.113 +/- 0.06)%, respectively. In the peak period of callus formation, vincamine content in callus of leaf blades, stalks, root segment was (0.024 +/- 0.0025)%, (0.016 +/- 0.0015)%, (0.010 +/- 0.0015)%, respectively. To 30 days of subculture, vincamine content in callus of leaf blades, stalks, root segment was (0.041 +/- 0.002)%, (0.019 +/- 0001)%, (0.016 +/- 0.002)%, respectively. CONCLUSION: The optimal hormone combination for callus initiation was MS +2, 4-D 1.0 mg x L(-1) +6-BA 0.5 mg x L(-1) + NAA 0.5 mg x L(-1). In different growth periods, vincamine content in sterile plants is significantly different. From different explants in callus vincamine content is different, in which leaves callus is significantly higher than that of stems, roots produced callus organization.

Development and validation of an adsorptive stripping voltammetric method for the quantification of vincamine in its formulations and human serum using a Nujol-based carbon paste electrode.

An easy, rapid and selective adsorptive stripping voltammetry (AdSV) method for the determination of vincamine in its formulation and human serum was developed and validated. It was based on the oxidation of the drug onto a Nujol-based carbon paste electrode. The stripping step was carried out by using a square-wave (SW) potential-time voltammetric excitation signal. The optimal experimental variables as well as accumulation parameters were investigated as; frequency f=120 Hz, scan increment DeltaE(i)=10 mV, pulse-amplitude DeltaE(a)=25 mV and an accumulation potential E(acc) of 0.0 V using a Britton-Robinson (B-R) universal buffer of pH 5 as a supporting electrolyte. After validation of the described method, it was applied for determination of vincamine in its formulation and human serum. Mean recovery of 100.41+/-0.74 (n=5) was achieved for assay of vincamine in Oxybral capsules. Limits of detection and quantitation of 6.0 x 10(-9) M (2.20 ng ml(-1)) and 2 x 10(-8) M (7.33 ng ml(-1)) vincamine were achieved in human serum with a mean recovery of 99.5+/-1.79%, without prior extraction of the drug. No interferences were observed in formulation and/or human serum. Due to high sensitivity and specificity of the developed method, it was successfully applied for evaluating some pharmacokinetic parameters of two healthy volunteers after administration of a single oral Oxybral capsule.

Smart stability-indicating spectrophotometric methods for determination of binary mixtures without prior separation.

Ratio subtraction and isosbestic point methods are 2 innovating spectrophotometric methods used to determine vincamine in the presence of its acid degradation product and a mixture of cinnarizine (CN) and nicergoline (NIC). Linear correlations were obtained in the concentration range from 8-40 microg/mL for vincamine (I), 6-22 microg/mL for CN (II), and 6-36 microg/mL for NIC (III), with mean accuracies 99.72 +/- 0.917% for I, 99.91 +/- 0.703% for II, and 99.58 +/- 0.847 and 99.83 +/- 1.039% for III. The ratio subtraction method was utilized for the analysis of laboratory-prepared mixtures containing different ratios of vincamine and its degradation product, and it was valid in the presence of up to 80% degradation product. CN and NIC in synthetic mixtures were analyzed by the 2 proposed methods with the total content of the mixture determined at their respective isosbestic points of 270.2 and 235.8 nm, and the content of CN was determined by the ratio subtraction method. The proposed method was validated and found to be suitable as a stability-indicating assay method for vincamine in pharmaceutical formulations. The standard addition technique was applied to validate the results and to ensure the specificity of the proposed methods.

Simultaneous determination of piracetam and vincamine by spectrophotometric and high-performance liquid chromatographic methods.

A mixture of piracetam and vincamine was determined by 3 different methods. The first was the determination of piracetam and vincamine using the ratio-spectra first-derivative (DD1) spectrophotometric technique at 209 and 293 nm in concentration ranges of 10-45 and 2-14 microg/mL with mean recoveries of 99.22 +/- 0.72 and 99.67 +/- 0.79%, respectively. The second method was based on the resolution of the 2 components by bivariate calibration depending on a mathematic algorithm that provides simplicity and rapidity. The method depended on quantitative evaluation of the absorbencies at 210 and 225 nm in concentration ranges of 5-45 and 2-14 microg/mL, with mean recoveries of 100.33 +/- 0.54 and 100.44 +/- 0.98% for piracetam and vincamine, respectively. The third method was reversed-phase liquid chromatography using 0.05 M potassium dihydrogen phosphate-methanol (50 + 50, v/v) as the mobile phase, with the pH adjusted to 3.5 with phosphoric acid. The eluent was monitored at 215 nm in concentration ranges of 5-100 and 2-200 microg/mL, with mean recoveries of 99.62 +/- 0.67 and 99.32 +/- 0.85% for piracetam and vincamine, respectively. The suggested procedures were checked using laboratory-prepared mixtures and were successfully applied for the analysis of their pharmaceutical preparation. The methods retained their accuracy and precision when applying the standard addition technique. The results obtained by applying the proposed methods were statistically analyzed and compared with those obtained by the manufacturer's method.

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.

Pharmacokinetics and metabolism of vincamine and related compounds.

The pharmacokinetics and metabolism of vincamine, vinpocetine, methylene-methoxy-apovincaminic acid ester and eburnamine have been reviewed. The main route of elimination for vincamine, vinpocetine and methylene-methoxy-apovincaminic acid ester is ester cleavage and conjugation in the case of eburnamine. Vincamine and its derivatives show significant differences in metabolic pathway and their elimination is rapid in the species studied. Emphasis has been placed on the analytical methods used for monitoring these drugs in biological systems.

[Quantitative determination of drugs by in situ spectrophotometry of chromatograms for pharmacokinetic studies. I. Sulpiride and other benzamides, vincamine, naftazone (author's transl)]. / Dosage des médicaments par spectrophotométrie in situ des chromatogrammes en vue de leur étude pharmacocinétique. I. Sulpiride et autres benzamides, vincamine, naftazone.

Assays are proposed for sulpiride and other benzamides, vincamine and naftazone in plasma (or blood) and urine with direct UV reflectance spectrophotometry on this are applied directly on TLC along with a calibration curve on each plate. Plasma (or total blood) samples are extracted, and an internal standard is added before aplication; slopes of the obtained calibration curves do not change significantly from plate to plate, thus allowing several determinations on the same plate. The sensitivity is 2 microgram in a 1-ml sample (amount applied 30 ng) for sulpiride and related compounds and about the same for vincamine. Naftazone is determined in plasma with simultaneous reflectance and transmittance spectrophotometric measurements at 520 nm on chromatoplates sprayed with lead acetate, the sensitivity reached is 10 ng in a 1-ml sample (amount applied 0.5 ng). For all drugs studied, the proposed techniques are specific, reliable and sensitive enough and can be used to perform pharmacokinetic studies in human or in animal after administration of doses in the therapeutic range.