Simultaneous RP-HPLC method for the stress degradation studies of atorvastatin calcium and ezetimibe in multicomponent dosage form

Se desarrolló y validó un método estable de cromatografía líquida de alta eficacia de fase reversa (RP-HPLC) para la estimación simultánea de atorvastatina de calcio y ezetimiba en su forma de dosificación multicomponente. El método RP-HPLC propuesto utiliza, a temperatura ambiente, una columna C-18 Phenomenex de 125 mm x 4,6 mm y d.i de 5 μm; la fase móvil óptima consta de acetonitrilo y 0,4% v/v de trietilamina (pH ajustado a 5,5 con ácido ortofosfórico) en una proporción de 55:45, v/v, respectivamente, y una velocidad de flujo de 1,0 ml/min. Las medidas se realizaron a una longitud de onda de 231 nm. La forma de dosificación multicomponente se expuso a estrés oxidativo, hidrolítico, fotolítico y térmico. No se observaron, en la degradación de productos, ni impurezas ni picos de coelución o interferencia por excipientes, y, además, el método resultó ser específico. El método fue linear, en el rango de 5-25 μg/ml para atorvastatina de calcio y ezetimiba. Las recuperaciones medias fueron del 98,82% y 98,72% para atorvastatina de calcio y ezetimiba, respectivamente. El método se validó para linealidad, rango, precisión, exactitud, especificidad, selectividad, precisión intermedia, dureza, robustez, estabilidad de la disolución e idoneidad.A stability-indicating reversed-phase high performance liquid chromatographic (RP-HPLC) method has been developed and validated for simultaneous estimation of atorvastatin calcium and ezetimibe for their multicomponent dosage form. The proposed RP-HPLC method utilizes a 125 mm x 4.6 mm i.d 5 μm Phenomenex C-18 column at ambient temperature; the optimum mobile phase consists of acetonitrile and 0.4% v/v triethylamine (pH adjusted to 5.5 with ortho-phosphoric acid) in the ratio of 55:45, v/v respectively, flow rate of 1.0 ml/min. Measurements were made at a wavelength of 231 nm. Multicomponent dosage form was exposed to thermal, photolytic, hydrolytic and oxidative stress. No co eluting, interfering peaks from excipients, impurities were observed for the degradation products and hence the method was found to be specific. The method was linear in the range of 5-25 μg/ml for atorvastatin calcium and ezetimibe. The mean recoveries were 98.82% and 98.72% for atorvastatin calcium and ezetimibe respectively. The method was validated for linearity, range, precision, accuracy, specificity, selectivity, intermediate precision, ruggedness, robustness, solution stability and suitability

Gradijentna HPLC analiza raloksifen hidroklorida i primjena u kontroli kvalitete

A rapid, sensitive and selective method for the determination of raloxifene hydrochloride (RLX) in pure drug and in tablets was developed using gradient high performance liquid chromatography (HPLC). The devised method involved separation of RLX on a reversed phase Hypersil ODS column and determination with UV detection at 284 nm. The standard curve was linear (R = 0.999) over the concentration range of 50-600 μg mL1 with a detection limit of 0.04 μg mL1 and a quantification limit of 0.16 μg mL1. Intra-day and inter-day precision and accuracy of the method were established according to the current ICH guidelines. Intra-day RSD values at three QC levels (250, 450 and 550 μg mL1) were 0.20.5% based on the peak area. The intra-day relative error (er) was between 0.2 and 0.5%. The developed method was successfully applied to the determination of RLX in tablets and the results were statistically compared with those obtained by a literature method. Accuracy, evaluated by means of the spike recovery method, was excellent with percent recovery in the range 97.7103.2 with precision in the range 1.62.2%. No interference was observed from the conformulated substances. The method was economical in terms of the time taken and the amount of solvent used.Koristeći gradijentnu tekućinsku kromatografiju visoke učinkovitosti razvijena je brza, osjetljiva i selektivna metoda za određivanje raloksifen hidroklorida (RLX), čiste supstancije i u tabletama. U radu je primijenjena reverzno-fazna kolona Hypersil ODS te UV detekcija pri 284 nm. Standardna krivulja bila je linearna (R = 0,999) u koncentracijskom području 50600 μg mL1. Granica detekcije bila je 0,04 μg mL1 a granica određivanja 0,16 μg mL1. Repetabilnost, intermedijalna preciznost i ispravnost ispitivane su prema važećim ICH uputama. Mjerenjem površine ispod pika na tri koncentracijske razine (250, 450 i 550 μg mL1) procijenjena je repetabilnost na 0,20,5%. Relativna pogreška procijenjena unutar jednog dana (er) bila je između 0,2 i 0,5%. Razvijena metoda uspješno je primijenjena za određivanje RLX u tabletama. Rezultati su statistički uspoređeni s rezultatima dobivenim prema ranije objavljenoj metodi. Analitički povrat bio je u rasponu 97,7103,2 uz preciznost od 1,6 do 2,2%. Nije primijećena interferencija pomoćnih tvari. Metoda je ekonomična s obzirom na utrošeno vrijeme i količine upotrebljenog otapala

Development of 2nd generation aminomethyl spectinomycins that overcome native efflux in Mycobacterium abscessus

Mycobacterium abscessus (Mab), a nontuberculous mycobacterial (NTM) species, is an emerging pathogen with high intrinsic drug resistance. Current standard-of-care therapy results in poor outcomes, demonstrating the urgent need to develop effective antimycobacterial regimens. Through synthetic modification of spectinomycin (SPC), we have identified a distinct structural subclass of N-ethylene linked aminomethyl SPCs (eAmSPCs) that are up to 64-fold more potent against Mab over the parent SPC. Mechanism of action and crystallography studies demonstrate that the eAmSPCs display a mode of ribosomal inhibition consistent with SPC. However, they exert their increased antimicrobial activity through enhanced accumulation, largely by circumventing efflux mechanisms. The N-ethylene linkage within this series plays a critical role in avoiding TetV-mediated efflux, as lead eAmSPC 2593 displays a mere fourfold susceptibility improvement against Mab ΔtetV, in contrast to the 64-fold increase for SPC. Even a minor shortening of the linkage by a single carbon, akin to 1st generation AmSPC 1950, results in a substantial increase in MICs and a 16-fold rise in susceptibility against Mab ΔtetV. These shifts suggest that longer linkages might modify the kinetics of drug expulsion by TetV, ultimately shifting the equilibrium towards heightened intracellular concentrations and enhanced antimicrobial efficacy. Furthermore, lead eAmSPCs were also shown to synergize with various classes of anti-Mab antibiotics and retain activity against clinical isolates and other mycobacterial strains. Encouraging pharmacokinetic profiles coupled with robust efficacy in Mab murine infection models suggest that eAmSPCs hold the potential to be developed into treatments for Mab and other NTM infections

Método simultáneo de RP-HPLC para los estudios de estrés degradativo de atorvastatina de calcio y ezetimiba en forma de dosificación multicomponente

A stability-indicating reversed-phase high performance liquid chromatographic (RP-HPLC) method has been developed and validated for simultaneous estimation of atorvastatin calcium and ezetimibe for their multicomponent dosage form. The proposed RP-HPLC method utilizes a 125 mm x 4.6 mm i.d 5 μm Phenomenex C-18 column at ambient temperature; the optimum mobile phase consists of acetonitrile and 0.4% v/v triethylamine (pH adjusted to 5.5 with ortho-phosphoric acid) in the ratio of 55:45, v/v respectively, flow rate of 1.0 ml/min. Measurements were made at a wavelength of 231 nm. Multicomponent dosage form was exposed to thermal, photolytic, hydrolytic and oxidative stress. No co eluting, interfering peaks from excipients, impurities were observed for the degradation products and hence the method was found to be specific. The method was linear in the range of 5-25 μg/ml for atorvastatin calcium and ezetimibe. The mean recoveries were 98.82% and 98.72% for atorvastatin calcium and ezetimibe respectively. The method was validated for linearity, range, precision, accuracy, specificity, selectivity, intermediate precision, ruggedness, robustness, solution stability and suitability.Se desarrolló y validó un método estable de cromatografía líquida de alta eficacia de fase reversa (RP-HPLC) para la estimación simultánea de atorvastatina de calcio y ezetimiba en su forma de dosificación multicomponente. El método RP-HPLC propuesto utiliza, a temperatura ambiente, una columna C-18 Phenomenex de 125 mm x 4,6 mm y d.i de 5 μm; la fase móvil óptima consta de acetonitrilo y 0,4% v/v de trietilamina (pH ajustado a 5,5 con ácido ortofosfórico) en una proporción de 55:45, v/v, respectivamente, y una velocidad de flujo de 1,0 ml/min. Las medidas se realizaron a una longitud de onda de 231 nm. La forma de dosificación multicomponente se expuso a estrés oxidativo, hidrolítico, fotolítico y térmico. No se observaron, en la degradación de productos, ni impurezas ni picos de coelución o interferencia por excipientes, y, además, el método resultó ser específico. El método fue linear, en el rango de 5-25 μg/ml para atorvastatina de calcio y ezetimiba. Las recuperaciones medias fueron del 98,82% y 98,72% para atorvastatina de calcio y ezetimiba, respectivamente. El método se validó para linealidad, rango, precisión, exactitud, especificidad, selectividad, precisión intermedia, dureza, robustez, estabilidad de la disolución e idoneidad

Synthesis and structure-activity relationship of thioacetamide-triazoles against Escherichia coli

Infections due to Gram-negative bacteria are increasingly dangerous due to the spread of multi-drug resistant strains, emphasizing the urgent need for new antibiotics with alternative modes of action. We have previously identified a novel class of antibacterial agents, thioacetamide-triazoles, using an antifolate targeted screen and determined their mode of action which is dependent on activation by cysteine synthase A. Herein, we report a detailed examination of the anti

Oscillation of second order difference equation with a sub-linear neutral term

This paper deals with the oscillation of a certain class of second order difference equations with a sub-linear neutral term. Using some inequalities and Riccati type transformation, four new oscillation criteria are obtained. Examples are included to illustrate the main results

Ternary mixed monolayers for simultaneous DNA orientation control and surface passivation for label free DNA hybridization electrochemical sensing

Target recognizing ternary mixed monolayer is constructed by simple sequential adsorption of thiol caped single stranded DNA (HS-ssDNA), 6-mercapto-1-hexanol (MCH) and 3-mercaptopropionic acid (MPA) diluents (abbreviated as HS-ssDNA/MPA/MCH) and applied for detection of DNA hybridization sequence by electrochemical method. The method is more reliable and reproducible on both conventional wire electrode and 100 nm scale gold-coated silicon chips. Detection limit of 10 pM is observed constantly on all types of electrodes. This ternary layer approach provides 60-80% discrimination effect between the hybridized and un-hybridized surfaces compared to the binary mixed monolayers HS-ssDNA/MCH and HS-ssDNA/MPA that showed 20-30% only. Characterization by impedance spectroscopy, X-ray photoelectron spectroscopy and surface Fourier Transform Infrared (FT-IR) techniques reveals 'head-to-head' anisotropic hydrogen bonding between MPA and MCH diluents that controls the HS-ssDNA orientation and enhancing the electrostatic blockade for K(3)[Fe(CN)(6)]. This is the first report characterizing the ternary layer for DNA molecular affinity sensing. Results provided unprecedented insight onto the label free electrochemical sensing and understanding of the complex sensing mechanism to develop sensors that is more reliable.close1

Synthesis and Structure–Activity Relationship of Thioacetamide-Triazoles against Escherichia coli

Infections due to Gram-negative bacteria are increasingly dangerous due to the spread of multi-drug resistant strains, emphasizing the urgent need for new antibiotics with alternative modes of action. We have previously identified a novel class of antibacterial agents, thioacetamide-triazoles, using an antifolate targeted screen and determined their mode of action which is dependent on activation by cysteine synthase A. Herein, we report a detailed examination of the anti-E. coli structure–activity relationship of the thioacetamide-triazoles. Analogs of the initial hit compounds were synthesized to study the contribution of the aryl, thioacetamide, and triazole sections. A clear structure–activity relationship was observed generating compounds with excellent inhibition values. Substitutions to the aryl ring were generally best tolerated, including the introduction of thiazole and pyridine heteroaryl systems. Substitutions to the central thioacetamide linker section were more nuanced; the introduction of a methyl branch to the thioacetamide linker substantially decreased antibacterial activity, but the isomeric propionamide and N-benzamide systems retained activity. Changes to the triazole portion of the molecule dramatically decreased the antibacterial activity, further indicating that 1,2,3-triazole is critical for potency. From these studies, we have identified new lead compounds with desirable in-vitro ADME properties and in-vivo pharmacokinetic properties