A new stability indicating reverse phase high performance liquid chromatography method for the determination of enantiomeric purity of a DPP-4 inhibitor drug linagliptin.

A simple, sensitive, and stability indicating isocratic reverse phase high performance liquid chromatography method has been developed, optimized and validated for the separation and quantification of S-enantiomer in linagliptin (R-enantiomer) drug substance. Enantiomeric separation was achieved on a Cellulose tris(4-chloro-3-methylphenylcarbamate) stationary phase. Mobile phase consists of aqueous diammonium hydrogen phosphate buffer and acetonitrile in the ratio of 35:65 v/v. Isocratic elution was performed at a flow rate of 1.0 mL/min, the column oven temperature was set at 40°C and detection was at 226 nm. The resolution between R and S enantiomers is found to be more than 4.0. The impact of mobile phase composition, pH of buffer and temperature on the resolution has been studied. The detector response is found to be linear over the concentration range of 0.17-1.7 µg/mL. LOD and LOQ levels of S-enantiomer are found to be 0.057 and 0.172 µg/mL respectively. The recovery of S-enantiomer is 99.8% w/w. The proposed method is validated for specificity, precision, linearity, accuracy and robustness.

Degradation studies of Ibrutinib under stress conditions: Characterisation and structural elucidation of novel degradants.

The aim of the research work is to study the degradation behaviour of Ibrutinib (IBN) which is performed under different stress conditions according to International Conference on Harmonization guidelines (ICH). The study included monitoring degradation of the Ibrutinib drug under acidic, base, oxidation, thermal and photolytic conditions followed by isolation and characterisation of degradation products (DP) by Liquid Chromatography Mass Spectrometry (LCMS), High resolution Mass Spectrometry (HR-MS/MS) and Nuclear Magnetic Resonance (NMR) studies. The IBN drug is stable under oxidation, thermal and photolytic conditions. The degradation of drug is observed under acidic and basic conditions. Two novel degradation products are formed which are not reported in the literature. The LCMS method has been developed for chromatographic separation of drug and its degradation products which were attained on C18 BEH UPLC column (50 mm X 2.1 mm, 1.7 µm). The combination of 0.05% Acetonitrile in water and 0.05% Formic acid in water are used as a mobile phase. The flow rate is 0.6 ml/min and UV wavelength monitored at 215 nm. Acetonitrile and water are used as diluents.

Separation of Unprecedented Degradants of Domperidone by Ultra-Performance Convergence Chromatography and Their Structure Elucidation.

Domperidone, a gastroprokinetic agent, is a common drug to treat emesis. It was subjected to acid, base-mediated hydrolysis, peroxide-mediated oxidation, photolysis and thermal degradation according to ICH guidelines to observe stability of the selected drug under the stress conditions. Although the drug is resistant to base hydrolysis, photolysis and thermal stressors, two degradants (DP-ISO1 and DP-ISO2) were formed in acid mediated hydrolysis. Oxidation with hydrogen peroxide also resulted in one product (DP-OX). All three degradants were isolated from the crude reaction mixture by preparative high-performance liquid chromatography and supercritical fluid chromatography. Structures of isolated compounds were unambiguously characterized as 5-chloro-1-(1-(3-(6-chloro-2-oxo-2,3-dihydro-1H-benzo[d]imidazol-1-yl)propyl)piperidin-4-yl)-1,3-dihydro-2H-benzo[d]imidazol-2-one (DP-ISO1), 5-chloro-1-(3-(4-(5-chloro-2-oxo-2,3-dihydro-1H-benzo[d]imidazol-1-yl)piperidin-1-yl)propyl)-1,3-dihydro-2H-benzo[d]imidazol-2-one (DP-ISO2), 4-(5-chloro-2-oxo-2,3-dihydro-1H-benzo[d]imidazol-1-yl)-1-(3-(2-oxo-2,3-dihydro-1H-benzo[d]imidazol-1-yl)propyl)piperidine 1-oxide (DP-OX) by analysis of mass spectrometry, 1D and 2D nuclear magnetic resonance spectra. To the best of our knowledge, DP-ISO1 and DP-ISO2 are new and DP-OX was previously reported as domperidone impurity.

Structure elucidation of novel degradation products of thiocolchicoside by NMR spectroscopy.

Thiocolchicoside is a natural product analogue often used for its spasmolytic action. To know more about its stability under various stress conditions, the drug was stirred in acid, base and peroxide solutions. In acid hydrolysis, two products were obtained and in both, the glucose got cleaved. In one of them the acetyl group also got cleaved. A set of two diastereomers were formed during the peroxide mediated hydrolysis. The base mediated hydrolysis resulted in formation of three novel degradants. They have six membered rings in their structures instead of a seven membered cycloheptatrienone. Structures of known and novel degradation products have been elucidated by extensive analysis of HRMS, 1D and 2D NMR spectroscopic techniques.

Degradation study of irbesartan: Isolation and structural elucidation of novel degradants.

To assess the stability of Irbesartan under stress conditions, and identify the degradation products, it was subjected to hydrolytic and oxidative stress, according to ICH guideline Q1A (R2). The drug showed degradation only in basic conditions, while it was stable to other stress conditions. Three degradation products were formed, which were separated on a C-8 column employing prep HPLC using gradient elution. The structures were established by extensive 1D and 2D NMR spectroscopic studies and mass spectra. The products were identified as (2'-(2H-tetrazol-5-yl)-[1,1'-biphenyl]-4-yl)methanamine (DP-1), N-((2'-(2H-tetrazol-5-yl)-[1,1'-biphenyl]-4-yl)methyl)pentanamide (DP-2) and N-((2'-(2H-tetrazol-5-yl)-[1,1'-biphenyl]-4-yl)methyl)-1-pentanamidocyclopentane-1-carboxamide (DP-3). One of the three, DP-1, was reported earlier. However, its structure has not been elucidated by NMR. The other two degradants are novel and are being reported here for the first time.

Synthesis and characterization of potential dimers of gatifloxacin - an antibacterial drug.

Gatifloxacin is an antibacterial agent belonging to the fourth-generation fluoroquinolone family. Four piperazine-linked fluoroquinolone dimers of Gatifloxacin were observed during the laboratory process for Gatifloxacin and they were identified. The present work describes the origin, synthesis, characterization, and control of these dimers along with the synthesis of Despropylene Gatifloxacin (metabolite).