Analysis of cassine and spectaline in the Senna spectabilis ethanolic extracts by capillary zone electrophoresis with indirect UV detection.

INTRODUCTION: 2,6-Disubstituted piperidin-3-ols are an important group of piperidine alkaloids found in species such as Senna spectabilis, whose main constituents include cassine and spectaline, compounds with relevant pharmacological activity. The analysis of these compounds is challenging due to the complexity of plant extracts and the absence of chromophores capable of absorbing ultraviolet (UV) radiation. OBJECTIVE: This paper presents a new analytical method to separate and quantify the non-UV-absorbing alkaloids present in ethanol extracts from S. spectabilis flowers using capillary zone electrophoresis (CZE) with indirect UV detection. METHODOLOGY: The optimized CZE method employs a background electrolyte containing 60 mM histidine (His), 15 mM α-cyclodextrin, 20% acetonitrile (ACN), and pH-adjusted to 4.7 with acetic acid (AcOH). RESULTS: The limit of detection (LOD) values was 10.2 and 13.9 mg L-1 for cassine and spectaline, respectively. For both analytes, the precision data were better than 2% of relative standard deviation (RSD) for migration times and peak areas. To evaluate the applicability of the developed method, ethanolic extracts from S. spectabilis flowers were prepared and analyzed. CONCLUSIONS: Thereby, the method proved to be efficient and complementary to conventional techniques, offering a cost-effective alternative in the quantification of the non-UV-absorbing piperidine alkaloids present in plant extracts.

Concurrent Determination of Pridinol, Diclofenac and Impurity A by HPLC-UV.

A reversed-phase high-performance liquid chromatography method was developed and validated for the simultaneous determination of pridinol, diclofenac and diclofenac-related compounds in tablet formulations. The proposed method is also suitable for content uniformity determination, for dissolution test and for stability studies. Separation was achieved on a base-deactivated silica C8 column, using 50 mM phosphate buffer (pH 2.5) and methanol (40:60 v/v) as mobile phase, at a flow rate of 1.0 mL/min and column temperature of 40°C. Ultraviolet detection was made at 225 nm. The method was validated for specificity, accuracy, precision (intraday and interday levels) and linearity for each analyte. For diclofenac impurity A, sensitivity was also studied. The method showed specificity and linearity (R2: 0.999 for the three analytes) over the assessed concentration range (diclofenac: 2.5-75.0 µg/mL, pridinol: 2.0-60.0 µg/mL and impurity A: 1.25-5.0 µg/mL) and demonstrated good precision as reflected by the low coefficient of variation in all cases. Recovery rates obtained were 99.81, 100.58 and 100.96% for diclofenac, pridinol and impurity A respectively, and for all three analytes, the variances of the concentrations tested were equivalent. The detection and quantitation limits for impurity A were 0.078 and 0.261 µg/mL, respectively.

Bilastine: Quantitative Determination by LC with Fluorescence Detection and Structural Elucidation of the Degradation Products Using HRMS.

BACKGROUND: A liquid chromatography (LC) stability-indicating method was developed and validated for the quantitative determination of bilastine in coated tablets. OBJECTIVE: The procedure was validated for specificity, linearity, robustness, precision, and accuracy. Plackett-Burmann experimental design was used to determine the robustness of the method. METHOD: Chromatographic separation was performed on a Shim-pack® RP-18 column with fluorescence detection. The degradation products formed under oxidative conditions were isolated and identified using high-resolution mass spectrometry (HRMS). In silico prediction of degradation products and in silico toxicity studies were also performed. RESULTS: The LC method presented good recovery and precision (intraday and interday), the response was linear in a range of 0.20 to 0.70 µg mL-1, and the results demonstrated the robustness of the analytical method under the evaluated conditions. CONCLUSIONS: The degradation products were identified as benzimidazole (DP1) and amine N-oxide of bilastine (DP2). The results for the toxicity studies demonstrated the high mutagenic potential of DP1 and hepatotoxicity and hERG I inhibitor effects of DP2. HIGHLIGHTS: Bilastine degradation products were identified as benzimidazole and amine N-oxide using HRMS.

Characteristics, Biological Properties and Analytical Methods of Piperine: A Review.

Piperine (PIP) is a natural alkaloid isolated from Piper longum L. that presents antioxidant, anticonvulsant, antimicrobial, neuroprotective, larvicidal, antiparasitic, anticancer effect and other pharmacological properties. However, the low aqueous solubility is the main barrier to its development from the laboratory to the clinic as a drug. Several strategies have been used to overcome this obstacle, like the incorporation of PIP into different drug delivery systems turned out to be highly efficient. In addition, several methods for the quantitative and qualitative analysis of PIP in various raw materials, including biological fluids (plasma, urine, metabolites, brain), plants and drug delivery systems, were investigated. Most recently high-performance liquid chromatography was used together with several detectors for this purpose. Therefore, this review presents a summary of characteristics chemical and biological properties of PIP as well as several techniques and analytical methods to optimize the analytical signal, increase sensitivity, selectivity and reduce the effects of interference for this drug.

Simultaneous determination of the quaternary ammonium pesticides paraquat, diquat, chlormequat, and mepiquat in barley and wheat using a modified quick polar pesticides method, diluted standard addition calibration and hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry.

In this study, a modified Quick Polar Pesticides (QuPPe) method, optimized by a central composite design, was developed to determine quaternary ammonium pesticides (QUATs) residues in barley and wheat by ultra-high-performance liquid chromatographic tandem mass spectrometry (UHPLC-MS/MS) using a hydrophilic interaction chromatography (HILIC) column. Considering the high polarity of these compounds, special conditions of sample preparation and analysis are required. Different mobile phases, extraction procedure and clean-up were evaluated. An isocratic elution with aqueous solution of ammonium formate 60 mmol L-1 (pH 3.7) and acetonitrile, 40:60 (v/v), was selected. Water and acidified methanol as extraction solvent, without heating, and a clean-up with dichloromethane, chitosan and acetonitrile presented good results. The validated method presented satisfactory selectivity, linearity, matrix effect, trueness and precision, providing recoveries from 93 to 110% with RSD < 13% for barley, and 70 to 115% with RSD < 18% for wheat. The complexity of these matrices requires the calibration in matrix and the diluted standard addition calibration (DSAC) procedure has been shown to be an excellent option to compensate for the matrix effect and the losses of the analytes in the extraction. Real samples of barley and wheat were analyzed and 60% presented concentrations of paraquat above the maximum limits allowed by the European Union. The modified QuPPe method combined with DSAC and HILIC-UHPLC-MS/MS demonstrated to be an effective approach to determine QUATs in barley and wheat, and is a good alternative for routine analysis. The use of the biosorbent chitosan is effective, low cost and more ecological when compared to others conventional sorbents.

Mass spectrometry for characterization of homologous piperidine alkaloids and their activity as acetylcholinesterase inhibitors.

RATIONALE: Piperidine alkaloids from Senna spectabilis constitute a rare class of natural products with several biological activities. However, the absence of chromophores makes their structural elucidation by conventional methods a great challenge. In this context, mass spectrometry emerges as a powerful tool for metabolomics studies. METHODS: The piperidine alkaloids (-)-cassine and (-)-spectaline and the semisynthetic derivatives (-)-3-O-acetylcassine and (-)-3-O-acetylspectaline were investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS) in the positive mode and electron ionization mass spectrometry (EI-MS). ESI fragmentation studies were performed with a quadrupole time-of-flight instrument; N2 was used as collision gas. The acetylcholinesterase inhibitory activity of the investigated compounds was evaluated by bioautography and microplate screening assays. RESULTS: ESI-MS/MS and EI-MS provided valuable and complementary information about the structure of the piperidine compounds. Collision-induced dissociation experiments (MS/MS) revealed that neutral elimination of water or acetic acid is the major fragmentation pathway, which agrees with the stereochemistry proposed for (-)-cassine and (-)-spectaline and the semisynthetic derivatives (-)-3-O-acetylcassine and (-)-3-O-acetylspectaline. CONCLUSIONS: The ESI-MS/MS and EI-MS studies allowed us to propose fragmentation mechanisms for piperidine alkaloids and derivatives. Therefore, mass spectrometry is an important tool for characterizing the structure of these compounds and for supporting further metabolomics studies.

A Critical Review of Physicochemical Properties and Analytical Methods Applied to Quantitative Determination of Ebastine.

Allergic diseases are the most common conditions in children and the second most frequent in adults. Currently, there are two well-defined generations of antihistamines, those belonging to first generation, with inherent side effects such as drowsiness and anticholinergic effects. These side effects are often attributed to their high lipophilicity and high affinity for brain H1 receptors. The ebastine is a modern antihistaminic drug belongs to the second generation and has lower lipophilicity, which diminish the undesirable side effects. To ensure the quality, efficacy, safety, and effectiveness of ebastine drug products, efficient and reliable analytical methods are mandatory. Besides official compendial methods, alternative methods are often developed and used in quality control of pharmaceuticals as well as in pharmacokinetic studies. In this work, we present a critical review on characteristics, physicochemical properties, and analytical methods applied in the analysis of ebastine.

Analytical Stability-Indicating Methods for Alogliptin in Tablets by LC-CAD and LC-UV.

Stability-indicating LC methods using a UV detector and a charged aerosol detector (CAD) simultaneously were validated for the assessment of alogliptin (ALG) in tablets. The analysis was performed on a C8 column (250 × 4.6 mm, 5 µm) at a flow of 0.8 mL/min, using acetonitrile-10 mM ammonium acetate buffer (pH 3.5; 90 + 10, v/v) as mobile phase and UV detection at 275 nm. Validation followed the International Conference on Harmonization guidelines. The method was linear over the range of 25-200 µg/mL. Normality of the residuals showed a normal distribution, no autocorrelation, and homoscedasticity. LODs were 6.25 and 2.65 µg/mL and LOQs were 20.85 and 8.84 µg/mL for the CAD and the UV detector, respectively. The methods were precise and accurate. Excipients and degradation products did not interfere in the methods in studies of specificity. None of the factors studied in the analysis of robustness had a significant effect on the quantification of the ALG by the Pareto chart. The results of the assay obtained with LC-CAD and LC-UV were similar. The methods could be considered interchangeable and stability-indicating, and can be applied as an appropriate QC tool for analysis of ALG in tablets.

Piperidine alkaloids from Lobelia polyphylla Hook. & Arn. (Campanulaceae) / Alcaloides piperidínicos de Lobelia polyphylla Hook. & Arn. (Campanulaceae)

The piperidine alkaloid composition from young stems of Lobelia polyphylla Hook & Arn. was determined by gas chromatography mass spectrometry (GC-MS). The tentative structures, without the stereochemistry, were obtained by the analysis of the fragmentation patterns of the mass spectra of each compound. The stems contained a mixture of lobeline (1), norlobelanidine (2), 1-(1-(2-hydroxy-2-phenylethyl)-1-methylpiperidin) butane-2-ol (3), 8-propyl-10-phenyl lobelionol (4), 1-(6-(2-hydroxy-2-phenylethyl)-1-methylpiperidin) butane-2-one (5), 1-(6-(2-hidroxypentyl)-1-ethylpiperidin) butane-2-one (6) and 1-methyl-2-piperidinemethanol (7). The role of these alkaloids in the toxic, narcotic and hallucinogenic effects, produced after smoking the aerial parts of this species is discussed.

La composición de alcaloides piperidínicos de tallos jóvenes de Lobelia polyphylla Hook & Arn. se determinó por cromatografía de gases acoplada a espectrometría de masas (CG-EM). Las estructuras tentativas sin incluir la estereoquímica, se obtuvieron mediante el análisis de los patrones de fragmentación de los espectros de masas de cada compuesto. Los tallos contienen una mezcla de lobelina (1), norlobelanidina (2), 1-(1-(2-hidroxi-2-feniletil)-1-metilpiperidin) butano-2-ol (3), 8-propil-10-fenil lobelionol (4), 1-(6-(2-hidroxi-2-feniletil)-1-metilpiperidin) butano-2-ona (5), 1-(6-(2-hidroxypentyl)-1-etilpiperidin) butano-2-ona (6) y 1-metil-2-piperidinmetanol (7). Se discute el posible papel de estos alcaloides en los efectos tóxicos, estupefacientes y alucinógenos, producidos después de haber fumado la parte aérea de esta especie.

Characterization of the allergen Sol gem 2 from the fire ant venom, Solenopsis geminata

Sol i 2 is a potent allergen in Solenopsis invicta venom, and most humans exhibit reactivity to it. The Sol gem 2 allergen found in the venom of the Thai tropical fire ant Solenopsis geminata was analysed in the present study. The protein was present in higher amounts than other proteins, as determined by SDS-PAGE, and presumably has allergenic properties similar to those of Sol i 2. Sol gem 2 molecular weight is 28 and 15 kDa, respectively, under non-reducing and reducing conditions, indicating that its native form is a dimer. LC-MS/MS analysis confirmed its similarity to Sol i 2. The mono/dimeric form of Sol gem 2 was determined to be relevant by proteomic approach and immunoblotting. An anti-Sol gem 2 antibody was produced in mice, with a titer greater than 1:800 according to the Western blotting analysis. The Sol gem 2-neutralising activity of this antibody was determined in crickets. The paralytic dose 50 (PD50) of crude S. geminata venom was elevated from 0.18 mg/g of body weight to more than 0.90 mg/g of body weight after preincubation with antibody at a ratio of 1:1. These results suggest that Sol gem 2 plays an important role in mediating the effects of the piperidine derivatives in the venom.(AU)

Validated stability-indicating RP-HPLC method for the determination of rimonabant in a pharmaceutical dosage form.

A simple RP-HPLC method was developed and validated for the determination of rimonabant in a pharmaceutical dosage form. The separation was performed on a C18 column (150 x 4.6 mm id, 5 microm) with acetonitrile-water (75 + 25, v/v) mobile phase. The detection was achieved with a diode array detector at 215 nm. The method was linear in the concentration range of 0.5-50 microg/mL (r = 1) with an LOQ of 0.24 microg/mL. The specificity and stability-indicating capability of the method were proved through forced degradation studies, and it was shown that there was no increase of the cytotoxicity. Rimonabant was exposed to hydrolytic, oxidative, and photolytic stress conditions, and the samples were analyzed by the proposed method. Under optimized conditions, rimonabant was successfully separated from its degradation products within 10 min, and the resolution was found to be greater than 2. The RSD values for intraday and interday precision were always less than 2%. Interday accuracy ranged from 98.1 to 101.7% (RSD = 1.0%). Moreover, method validation demonstrated acceptable results for sensitivity and robustness. The method was applied for the quantitative analysis of rimonabant in a tablet dosage form to demonstrate its use for improving the QC of pharmaceuticals containing this drug.

Voltammetric behavior of naratriptan and its determination in tablets.

The electrochemical behavior and the analytical application of the selective serotonin agonist naratriptan (N-methyl-3-(1-methyl-4-piperidyl)indole-5-ethanesulfonamide) are presented herein. Naratriptan exhibits an anodic response in aqueous media over a broad pH range (pH 2-12), as determined by differential pulse voltammetry and cyclic voltammetry using glassy carbon electrodes. This response is irreversible in nature, diffusion-controlled and probably caused by the oxidation of the naratriptan indole moiety. The differential pulse voltammetry technique was performed in 0.1 mol L(-1) Britton-Robinson buffer (pH=3), which elicited the most reproducible results. The percentage of naratriptan recovery was 102.1+/-1.8%, and the limits of detection and quantitation were 9.5x10(-6) and 2.0x10(-5) mol L(-1), respectively. Selectivity trials revealed that the oxidation signal of the drug was not disturbed by the presence of excipients or degradation products. Thus, we conclude that the method presented herein is useful for the quantification of naratriptan in pharmaceutical drugs and that this method requires no separations or extractions. Finally, this voltammetric method was successfully applied to determine the quantity and the content uniformity of naratriptan in drug tablets. A comparison of this technique to the standard high-performance liquid chromatography technique was conducted at the end of our study.

Development and validation of an HPLC method for the determination of process-related impurities in pridinol mesylate, employing experimental designs.

A simple high performance liquid chromatographic method for the determination of process-related impurities in bulk drug of the central anticholinergic compound pridinol mesylate, has been developed and validated. Spectroscopically characterized synthetic impurities were used as standards. The chromatographic separation was optimized employing an experimental design strategy, and was achieved on a C(18) column with a mobile phase containing 50mM potassium phosphate buffer (pH 6.4), MeOH and 2-propanol (20:69:11, v/v/v), delivered at a flow rate of 1.0mLmin(-1). UV detection was performed at 245nm. The optimized method was thoroughly validated, demonstrating to be selective, when the chromatogram was recorded with a diode-array detector and peak purities were evaluated (>0.9995). The method is robust and linear (r(2)>0.99) over the range 0.05-2.5% (5-250% with regards to the 1% specification limit for both process-related impurities); it is also precise, regarding repeatability (RSD

Validated stability-indicating HPLC method for the determination of pridinol mesylate. Kinetics study of its degradation in acid medium.

The stability of pridinol mesylate (PRI) was investigated under different stress conditions, including hydrolytic, oxidative, photolytic and thermal, as recommended by the ICH guidelines. Relevant degradation was found to take place under acidic (0.1N HCl) and photolytic (visible and long-wavelength UV-light) conditions, both yielding the product resulting from water elimination (ELI), while submission to an oxidizing environment gave the N-oxidation derivative (NOX). The standards of these degradation products were synthesized and characterized by IR, (1)H and (13)C NMR spectroscopy. A simple, sensitive and specific HPLC method was developed for the quantification of PRI, ELI and NOX in bulk drug, and the conditions were optimized by means of a statistical design strategy. The separation employs a C(18) column and a 51:9:40 (v/v/v) mixture of MeOH, 2-propanol and potassium phosphate solution (50mM, pH 6.0), as mobile phase, delivered at 1.0 ml min(-1); the analytes were detected and quantified at 220 nm. The method was validated, demonstrating to be accurate and precise (repeatability and intermediate precision levels) within the corresponding linear ranges of PRI (0.1-1.5 mg ml(-1); r=0.9983, n=18) and both impurities (0.1-1.3% relative to PRI, r=0.9996 and 0.9995 for ELI and NOX, respectively, n=18). Robustness against small modifications of pH and percentage of the aqueous mobile phase was ascertained and the limits of quantification of the analytes were also determined (0.4 and 0.5 microg ml(-1); 0.04% and 0.05% relative to PRI for ELI and NOX, respectively). Peak purity indices (>0.9997), obtained with the aid of diode-array detection, and satisfactory resolution (R(s)>2.0) between PRI and its impurities established the specificity of the determination, all these results proving the stability-indicating capability of the method. The kinetics of the degradation of PRI in acid medium was also studied, determining that this is a first-order process with regards to drug concentration, with an activation energy of 25.5 Kcal mol(-1) and a t(1/2)=10,830 h, in 0.1N HCl at 38 degrees C.

Method development and validation for the simultaneous determination of meloxicam and pridinol mesylate using RP-HPLC and its application in drug formulations.

A simple and reliable reversed-phase high-perfomance liquid chromatographic method has been developed and validated for the simultaneous determination of meloxicam and pridinol mesylate in their synthetic mixtures and combined tablet formulations. Both drugs were separated on a 250 mm x 4.6mm C18 column packed with 5 microm particles. The mobile phase, optimized through an experimental design, was a 51:9:40 (v/v/v) mixture of methanol, isopropanol and 50mM potassium phosphate buffer (pH 5.9), pumped at a flow rate of 1.0 ml min(-1). UV detection was performed at 225 nm. The method was validated in the sample concentration ranges of 33.7-61.8 mg l(-1) for meloxicam and 8.8-16.8 mg l(-1) for pridinol mesylate, where it demonstrated good linearity with r=0.9989 and 0.9987 (n=15), respectively. The assay was shown to be repeatable at concentration levels of 70%, 100% and 130%, with relative standard deviation values of 1.09% and 0.82% for meloxicam and pridinol, respectively. For independent 100% level samples, the intra-day precision was 0.4% and 1.0% while the intermediate precision was 0.7% and 1.0% for the drugs. The method demonstrated to be robust, resisting to small deliberate changes in pH, flow rate and composition (organic:aqueous ratio) of the mobile phase. The LOD values were 0.22 and 0.20 mg l(-1), while the LOQ were 1.7 and 1.1 mg l(-1), for meloxicam and pridinol, respectively. The applicability of the method was demonstrated by determining the drug content of two commercial pharmaceutical formulations, where it exhibited good performance.

New antihistamines: a critical view

OBJETIVO: Avaliar criticamente os mais novos anti-histamínicos anti-H1 e os diferentes termos utilizados para denominá-los, com base na revisão de evidências sobre o papel dos anti-H1 no tratamento das doenças alérgicas. FONTES DOS DADOS: Artigos originais, revisões e consensos indexados nos bancos de dados MEDLINE e PUBMED de 1998 a 2006. Palavra chave: anti-histamínicos. SíNTESE DOS DADOS: Os anti-histamínicos de segunda geração diferenciam-se dos de primeira geração por sua elevada especificidade e afinidade pelos receptores H1 periféricos e pela menor penetração no sistema nervoso central (SNC), com conseqüente redução dos efeitos sedativos. Embora os anti-histamínicos de segunda geração sejam, geralmente, melhor tolerados do que seus predecessores, alguns efeitos adversos, principalmente cardiotoxicidade, surgiram com alguns deles. Nos últimos 20 anos, novos compostos, com diferentes farmacocinéticas, foram sintetizados. A maioria deles manifesta propriedades antiinflamatórias que independem de sua atividade no receptor H1. Aprimoramentos mais recentes, geralmente na forma de metabólitos ativos, levaram ao uso do termo anti-histamínico de terceira geração. Esse termo surgiu espontaneamente, sem uma descrição clara de seu significado e implicações clínicas, criando grande confusão entre os profissionais da saúde. CONCLUSÕES: Com base nas evidências sobre anti-histamínicos anti-H1, nenhum deles pode ser considerado como "anti-histamínico de terceira geração". Para tanto, seria preciso comprovar que a nova classe de anti-histamínicos possui vantagens clínicas distintas sobre os compostos existentes e preenche pelo menos três pré-requisitos: ausência de cardiotoxicidade, de interações medicamentosas e de efeitos sobre o SNC.

OBJECTIVE: To perform a critical evaluation of the more recent H1 antihistamines and the various terms used to describe them, based on a review of evidence on their role in the treatment of allergic disorders. SOURCES: Original articles, reviews and consensus documents published from 1998 to 2006 and indexed in the MEDLINE and PubMed databases. Keyword: antihistamines. SUMMARY OF THE FINDINGS: Second-generation antihistamines differ from first-generation ones because of their elevated specificity and affinity for peripheral H1 receptors and because of their lower penetration of the central nervous system (CNS), having fewer sedative effects as a result. Whilst second-generation antihistamines are in general better tolerated than their predecessors, some adverse effects, principally cardiotoxicity, have been observed with some of them. Over the last 20 years, new compounds with different pharmacokinetic properties have been synthesized. The majority of these exhibit anti-inflammatory properties that are independent of their action on the H1 receptor. More recent improvements, generally in the form of active metabolites, led to the use of the term third-generation antihistamines. This term emerged spontaneously, with no clear definition of its meaning or clinical implications, creating great confusion among healthcare professionals. CONCLUSIONS: On the basis of the evidence on H1 antihistamines, none of them deserve the title"third-generation antihistamine." As the Consensus Group on New Generation Antihistamines concluded, to merit this definition, a new class of antihistamines would have to demonstrate distinct clinical advantages over existing compounds and fulfill at least three prerequisites: they should be free from cardiotoxicity, drug interactions and effects on the CNS.

Quantitative determination of anti-fungal and insecticide amides in adult plants, plantlets and callus from Piper tuberculatum by reverse-phase high-performance liquid chromatography.

A rapid, sensitive and reliable reverse-phase HPLC method was used for the quantitative determination of the anti-fungal and insecticide amides, dihydropiplartine (1), piplartine (2), deltaalpha,beta-dihydropiperine (3) and pellitorine (4) in plants in natura, in plantlets in vitro and ex vitro, and in callus of Piper tuberculatum. Well-resolved peaks were obtained with good detection response and linearity in the range of 15.0-3000 microg/mL. The plants in natura contained compounds 1-4, the plantlets ex vitro and in vitro accumulated compounds 1-2 and 1-4, respectively, while only amide 4 was found in callus.

HPLC analysis of 5H-benzo[a]carbazole with antifungal activity.

A sensitive and simple high-performance liquid chromatographic (HPLC) method for the assay of 6,11-dihydro-2-methoxy-5H-benzo[a]carbazole (1) and 6,11-dihydro-2-methoxy-11-[2-(1-piperidinyl)]ethyl-5H-benzo[a]carbazole (2) was developed. The procedure is based on the use of the reversed-phase high-performance liquid chromatographic (RP-HPLC) method with UV detector. Each analysis required no longer than 11 min. A linear relationship between the concentration of both the drugs and the UV absorbance at 254 nm was obtained. This linearity was maintained over the concentration ranged from 5 to 80 microg/ml. The detection limits were found to be 1.6 and 0.7 ng for compounds 1 and 2. The quantitation limits were found to be 5.3 and 2.5 ng for compounds 1 and 2, respectively. For recovery studies, several determinations were carried out. Recovery values ranged from 98 to 102.1% for compound 1 and from 98.4 to 101.6% for compound 2. Method precision was also evaluated and RSD% found was less than 2%. This method was applied without any interference from degradation products.

A new HPLC method to determine Donepezil hydrochloride in tablets.

A HPLC stability-indicating assay for Donepezil hydrochloride in tablets was developed and validated. Donepezil hydrochloride is a reversible inhibitor of acetylcholinesterase, indicated for the treatment of mild to moderate dementia of the Alzheimer's type. The HPLC method was performed with a reversed phase C18 column, detection at 268 nm and a mixture of methanol, phosphate buffer 0.02 M and triethylamine (50:50:0.5) as mobile phase. Typical retention time for Donepezil was 9 min. The method was statistically validated for linearity, accuracy, precision and selectivity following ICH recommendations. Due to its simplicity and accuracy, the method can be used for routine quality control analysis.