Drug Impurities Research Articles

Isolation, Characterization and Cumulative Quantification approach for nine organic impurities in empagliflozin and linagliptin drugs

Isolation, Characterization and Cumulative Quantification approach for nine organic impurities in empagliflozin and linagliptin drugs

Using PBMCs in a Multiplex FluoroSpot Assay for Detection of Innate Immune Response-Modulating Impurities (IIRMIs).

The ELISA-based monocyte activation test (MAT) facilitates the replacement of the rabbit pyrogen test (RPT) for the detection of Innate Immune Response-Modulating Impurities (IIRMIs) in injectable drugs by activation of monocytes in human peripheral blood mononuclear cells (PBMCs). We describe the use of a triple-color IL-1β/IL-6/TNF-α FluoroSpot assay as a sensitive tool for quantification of the frequencies of IIRMI-activated monocytes as well as determination of the relative amount of pyrogenic cytokine(s) produced by each activated cell.

A Review on The Impurity Profile of Pharmaceuticals

A collection of analytical procedures known collectively as “impurity profiling” are intended to detect, identify, clarify the structure of, and quantify both organic and inorganic impurities as well as residual solvents in pharmaceutical formulations and bulk pharmaceuticals. This is the main task of contemporary drug analysis since it is the most effective approach to describe the stability and quality of pharmaceutical formulations and bulk pharmaceuticals. To keep an eye on them, specific analytical techniques must be created. When modifications are made to the synthesis, formulation, or production processes, even if they are done to improve them, new purities could be seen. The identification of impurities in Active Pharmaceutical Ingredients (APIs) and the need for purity are being emphasised by a number of regulatory bodies, including the Canadian Drug and Health Agency (CDHA), the United States Food and Drug Administration (FDA), and the International Conference on Harmonisation (ICH). Pharmaceutical products can contain impurities from a variety of sources, including reagents, heavy metals, ligands, catalysts and other materials like charcoal, filter aids, and the like. Degraded end products from hydrolysis, photolytic cleavage, oxidative degradation, decarboxylation, and other processes can also contain impurities, as can enantiomeric impurities. The various pharmacopoeias, including the Indian, American, and British pharmacopoeias, are gradually adding restrictions to the permissible concentrations of contaminants found in APIs or formulations. Capillary electrophoresis, electron paramagnetic resonance, gas-liquid chromatography, gravimetric analysis, high performance liquid chromatography, solidphase extraction techniques, liquid-liquid extraction techniques, mass spectrometry, ultraviolet spectrometry, infrared spectroscopy, supercritical fluid extraction column chromatography, nuclear magnetic resonance (NMR) spectroscopy, and RAMAN spectroscopy are some of the techniques used to isolate and characterize impurities in pharmaceuticals. Liquid Chromatography (LC)-Mass Spectroscopy (MS), GC-MS, LC-NMR, LC- NMR-MS, and LC-MS are the most frequently used hyphenated techniques for drug impurity profiling. This demonstrates the importance and range of drug impurity profiling in pharmaceutical research.

New Validated LC-MS Method Development and Estimation of Nitrosamine impurities in Canaglifozin

Background: Canagliflozin is most prescribed anti-diabetic drug, as diabetic drugs are consumed daily there may be a chance of consuming nitrosamine impurities beyond their limits hence, the Food and Drug Association (FDA) recommends checking for carcinogenic impurities in routine use drugs. Aims and Objectives: The study aims to simultaneous estimation of 4 nitrosamines (NMDA, NEIA, NIEA, and NDIPA) by liquid chromatography-mass spectrometry (LCMS) to detect the limit of detection (LoD) and limit of quantitation (LoQ). estimation of these impurities (NMDA, NEIA) in canagliflozin tablet dosage form with specificity parameters. Methods: Drug canagliflozin was collected from hetero labs, methanol, LC-MS grade acetonitrile, formic acid four impurities (NMDA, NEIA, NDIPA, NIEA) purchased from Merck Pharmaceuticals Mumbai. The Zorbax SB C18 column (250 x 4.6 mm, 3 mcm) is used as the stationary phase, 0.1% formic acid and acetonitrile in the ratio of 70:30 is used as the mobile phase, methanol is used as diluent flow rate was maintained at 1-mL/min, the injection volume was fixed to 10 mcl, which is run at 10 minutes. The electron ionization ion source, multiple reaction monitoring, and acquisition mode is used for the study. The time required for the solvent delay and detector off is 4 and 9.5 minutes, respectively. The product ions peaks of impurities were observed at 44 for NDMA, 99 for NEIA. Results: The %RSD for the peak areas of NDMA, NEIA obtained from six replicate injections of standard solutions were 2.5, 9.8, 1.4 and 7.7, respectively. The %recovery of NDMA and NEIA were within the limit. The %RSD for the results obtained from the method precision study was within the limit. Conclusion: The above observations indicate that the LC-MS method meets the acceptance criteria for the parameters selected for the validation study. Hence, the method is suitable for the determination of NDMA, NEIA in a Drug Substance by LC-MS.

Characterization of Forced Degradation Products of Netarsudil: Optimization and Validation of a Stability-Indicating RP-HPLC Method for Simultaneous Quantification of Process-Related Impurities.

The aim of this study is to examine resolution, identification, and characterization of forced degradation products of netarsudil by liquid chromatography-tandem mass spectrometry by validating a simple and sensitive high-performance liquid chromatography method for the resolution, identification, and quantification of two process-related impurities in netarsudil. Chromatographic separation was accomplished on a ZORBAX Eclipse XDB C18 (250 x 4.6 mm; 5 µ id) column at room temperature as the stationary phase and 257 nm as the detector wavelength with the mobile phase consisting of acetonitrile, methanol, and pH 4.6 phosphate buffer in 45:35:20 (v/v) at 1.0 mL/min flow rate in isocratic elution. The method reported very sensitive detection limits of 0.008 µg/mL for impurity 1 and 0.003 µg/mL for impurity 1. The method produces a calibration curve linear in the concentration level of 25-200 for netarsudil and 0.025-0.2 µg/mL for impurities. The proposed method gives acceptable results for other validation parameters such as accuracy, precision, ruggedness, and robustness. The drug was subjected to various stress conditions such as acid, base, peroxide, and thermal and ultraviolet light to investigate the stability-indicating ability of the method. Considerable degradation was observed in stress studies, and the degradation products were well resolved from process-related impurities. The characterization of degradation products was performed on the basis of collision-induced dissociation mass spectral data, and the possible structures of the six degradation compounds of netarsudil were proposed. The outcomes of other validation studies were likewise satisfactory and proven adequate for the regular analysis of netarsudil and its process-related impurities in bulk drug and pharmaceutical dosage forms and can also be applied for the evaluation of the stress degradation mechanism of netarsudil.

Overcoming drug impurity challenges in amorphous solid dispersion with rational development of biorelevant dissolution-permeation method

Hot-melt extrusion is often used to prepare amorphous solid dispersion to overcome low drug solubility and enhance bio-performance of the formulation. Due to the uniqueness of each drug – polymer combination and its physico-chemical properties, setting the appropriate HME barrel temperature, feed rate and screw speed ensures drug amorphization, absence of residual crystallinity, absence of water, and a suitable drug release profile. In this research, samples with BCS II/IV model drug and PVP/VA polymer were prepared to evaluate the impact of HME process parameters, incoming drug form (anhydrous vs. hydrate), and drug supplier (i.e., impurity profile), on biorelevant drug release. This study provides a relationship between observed in vitro supersaturation and precipitation behavior of amorphous solid dispersion formulation with in vivo results, on patients, by using the acceptor profile of side-by-side dissolution-permeation apparatus.An in vitro dissolution method, in small volumes, in an apparatus with paddles and dissolution-permeation side-by-side method was developed on the MicroFlux™ apparatus to assess if the differences observed in vitro bears relevance to the bioequivalence outcome in vivo. The former was used to guide the generic drug product development due to high discriminatory strength, while the latter was biorelevant, due to the inclusion of the second compartment assuring absorptive environment to capture the impact of supersaturation and subsequent precipitation on bioavailability. Bio-relevancy of the in vitro method was confirmed with the in vivo dog study and clinical study on patients, and an in vitro – in vivo correlation was established.For the investigated BCS II/IV drug, this research highlights the importance of considering supersaturation and formation of colloidal species during amorphous solid dispersion release testing to assure product quality, safety and efficacy.

Development of stability-indicating HPLC method for quantification of pharmacopeia impurities of Zuclopenthixol and characterization of its stress degradation products by LCMS/MS

BackgroundThe present study focused to develop a simple and sensitive HPLC method for resolution and estimation process-related impurities of zuclopenthixol and further assessment of forced degradation behavior of zuclopenthixol.ResultsThe chromatographic separation of drug substance, process-related impurities and its degradation products (DPs) was achieved on KNAUER C18 (250 mm × 4.6 mm, 5µ id) column at that was maintained at 35 °C temperature using 0.1 M sodium acetate buffer at pH 4.3 and methanol in 20:80 (v/v) as mobile phase A, 0.1% formic acid and acetonitrile in 75:25 (v/v) as mobile phase B. Equal volume of mobile phase A and B was pumped in isocratic elution at 0.8 mL/min. Detection wavelength was selected as 257 nm. In the proposed conditions, zuclopenthixol is identified at 6.91 and 1.91 min and 2.89 min, respectively, for impurity B and A min with acceptable system suitability and specificity. The method produces LOD at 0.009 for impurities with calibration range of 30–180 µg/mL for zuclopenthixol and 0.03–0.18 µg/mL for impurities. The other validation parameters were notices to be with in the acceptable levels for zuclopenthixol and its impurities. The drug was exposed to different stressed conditions (acid, base, peroxide, thermal and UV light) according to ICH Q1A (R2) guidelines. The DPs formed during the stress study were identified and characterized by LCMS/MS in ESI positive mode.ConclusionThe analysis involved a comparison of collision-induced dissociation mass spectrometry data between the degradation products and zuclopenthixol. As a result, potential structures for six degradation compounds were suggested. The results from additional validation studies were similarly pleasing and demonstrated their suitability for the routine analysis of zuclopenthixol and its associated impurities in both bulk drug and pharmaceutical dosage forms. Additionally, these findings can be extended to assess the mechanism of stress degradation in zuclopenthixol.

Optimization of Stability-Indicating HPLC Method for Analyzing Process Related Impurities of Penfluridol and Structural Elucidation of Stress Degradation Products by LCMS/MSucidation of Stress Degradation Products by LCMS/MS

This study focused on the development of a simple and sensitive HPLC method for resolution and quantification of process-related impurities of penfluridol and further assessment of forced degradation behavior of penfluridol. The chromatographic separation was achieved on XTerra™ C18 (250×4.6 mm, 5.0μm) column and UV detection at 245nm. The mobile phase comprises of methanol and tetrahydrofuran in 55:45 (v/v) as solvent A and acetonitrile and tetrahydrofuran in 80:20 (v/v) as solvent B. The 60:40 (v/v) composition of solvent A and B were pumped isocratically at 1.0mL/min. In the proposed conditions, the retention time identified as 5.29 min for penfluridol, 4.51 min, 9.95 min and 7.64 min respectively for impurity 1, 2 and 3 with acceptable system suitability. The method produces sensitive detection limit of 0.008μg/mL for impurity 1, 2 and 0.004 μg/mL for impurity 3 with calibration range of 25-150 μg/mL for penfluridol and 0.025-0.150 μg/mL for impurities. The drug was exposed to different stressed conditions (acid, base, peroxide, thermal and UV light) according to ICH Q1A (R2) guidelines. The Degradation Products (DPs) formed during the stress study was characterized by LCMS/MS in ESI positive mode and the possible structures of five DPs with possible degradation pathways were proposed. The outcomes of other validation studies were likewise satisfactory and proven adequate for regular analysis of penfluridol and its process-related impurities in bulk drug and pharmaceutical dosage forms and can also applicable for evaluation of stress degradation mechanism of penfluridol.

Kinetic Optimization of the Batch Crystallization of an Active Pharmaceutical Ingredient in the Presence of a Low-Solubility, Precipitating Impurity

The presence of impurities above regulatory thresholds has been responsible for recent recalls of pharmaceutical drugs. Crystallization is one of the most used separation processes to control impurities in the final drug. A particular issue emerges when impurities are poorly soluble in the crystallization solvent and simultaneously precipitate with the product. This publication reports the development of a population balance model to investigate if the impurity crystallization kinetics can be selectively inhibited in a seeded batch crystallization system containing acetaminophen (ACM), a commonly used small-molecule active pharmaceutical ingredient (API), and curcumin (CUR), a simulated low-solubility/co-precipitating impurity. Raman spectroscopy was used in combination with a partial least squares (PLS) model for in situ monitoring of the crystallization process. The Raman data were integrated to calibrate a population balance model in gPROMS FormulatedProducts, to predict the evolution of the product’s purity throughout the process. Process optimization demonstrated that a high purity close to equilibrium is feasible within the first 2 h of crystallization, with ACM seed purity being the primary factor controlling this phenomenon. The optimal approach for kinetically rejecting impurities requires a low nucleation rate for the impurity, high product seed purities, and an adjustable crystallization time so the process can be stopped before equilibrium without allowing the impurity to nucleate. Overall, an improvement in product purity before equilibrium is attainable if there is enough difference in growth kinetics between the product and impurity, and if one can generate relatively pure seed crystals.

Potential degradation products of abemaciclib: Identification and structural characterization employing LC-Q/TOF-MS and NMR including mechanistic explanation

Degradation products are the potential drug impurities that can be generated during transport and storage of pharmaceuticals. Before this study, degradation chemistry and potential degradation products of abemaciclib (ABM) were unknown. Moreover, no stability-indicating analytical method was available that can be used to analyse ABM in presence of its degradation products. In this study, stress testing on ABM was carried out under oxidative, thermal, photolytic (UV & visible), and hydrolytic (acid, alkaline, and neutral) degradation conditions. The study revealed that ABM is susceptible to photolytic, oxidative, and thermal stress leading to the formation of five degradation products (DPs). ABM and its degradation products were chromatographically separated employing a developed RP-HPLC-based stability-indicating analytical method. The method was transferred to an LC-Q-TOF system for further analysis. To elucidate the structure of degradation products, fragmentation pathway of ABM was initially established through high-resolution mass spectrometry (HRMS). Subsequently, mass fragmentation pathways of all the DPs have been established through HRMS and MSn based analysis. The major degradation product was isolated and fully characterized using atmospheric chemical ionization-mass spectrometry and nuclear magnetic resonance techniques. ABM showed extensive degradation under oxidative and photolytic systems. Therefore, special care may be sought during storage and transport of ABM or its formulations to avoid photolytic and oxidative stress exposure to the drug. Lastly, in silico toxicity of the characterized degradation products was assessed employing ProTox ІІ online web predictor freeware in which some of them were found to have the potential of hepatotoxicity, immunogenicity and mutagenicity.

Review on LC-NMR Hyphenated Technique

A hyphenated technique refers to the integration of two distinct analytical methodologies to facilitate seamless interfacing. Typically, this involves the combination of chromatographic techniques with spectroscopic methods. LC-NMR, an influential analytical tool, has been instrumental in resolving intricate mixtures. LC-NMR, a hyphenated system that merges liquid chromatography (LC) with nuclear magnetic resonance (NMR), is a meticulously organized analytical approach extensively applied across various domains. These applications encompass the analysis of metabolites, profiling drug impurities, elucidating molecular structures, identifying volatile oils, scrutinizing pesticides, and investigating other natural products.

Development and Application of a Validated HPLC Method for the Determination of Alpelisib and its Process-Related Impurities in Pure Drug and Pharmaceutical Formulations

Impurity analysis plays a significant role in the manufacture of a safe pharmaceutical product that ensures the safety of consumers. Keeping this in consideration, the present study was intended to develop a simple and sensitive HPLC method for the resolution and quantification of 4 process-related impurities namely impurities 1, 2, 3 and 4 in alpelisib pure drug and formulations. The method consumes greener solvents as a mobile phase that resolves the analytes on ProntoSIL ODS-C18 (250×4.6 mm; 5 μ id) column at room temperature as stationary phase, ethanol and 0.1% aqueous acetic acid in 65:35 (V/V) at pH 4.5 as mobile phase at 0.8 mL/min flow rate, UV detection at 246 nm. The method can detect the analytes at retention times of 7.05, 4.52, 6.09, 2.88 and 8.14 min respectively for alpelisib, impurity 1, 2, 3 and 4. The analysis was completed with a run time of 15 min that consume less solvent and the same analysis time. The linearity of the proposed method was perceived in the range of 12.5 to 100 μg/mL for alpelisib and 0.0125 to 0.10 μg/mL for impurities. The method can effectively resolve the unknown stress degradation products generated during the stress exposure of alpelisib along with its known impurities in the study. The outcomes of other validation studies were likewise satisfactory and proven adequate for regular analysis of alpelisib and its process-related impurities in bulk drug and pharmaceutical tablet doses.

A sustainable data processing approach using ultraviolet-spectroscopy as a powerful spectral resolution tool for simultaneously estimating newly approved eye solution in the presence of extremely carcinogenic impurity aided with various greenness and whiteness assessment perspectives: Application to aqueous humor

Drug impurities are now seen as a major threat to drug safety around the world, especially when it comes to carcinogenic impurities. Here, we present the first spectrophotometric approach for the quantification of lignocaine and fluorescein in the presence of 2,6-xylidine, lignocaine’s carcinogenic impurity. The approach depends on overcoming unresolved bands through a data processing strategy employing 10 affordable, simple, and sensitive spectrophotometric methods. Fluorescein analysis (1–16 μg mL−1) was performed using direct ultraviolet spectrophotometry (D0) at 478 nm; then, the ratio subtraction method allowed the removal of interference caused by the fluorescein spectrum. From the resulting ratio spectra, 2,6-xylidine (40–160 μg mL−1) can be efficiently determined at 280 nm. However, lignocaine (72–320 μg mL−1) was analyzed using different ultraviolet-based methods, including continuous wavelet transform, ratio derivative by Savitzky–Golay filters, mean centering, second derivative of ratio spectra, ratio spectra difference spectrophotometry, extended ratio subtraction, absorbance subtraction, Q-absorbance ratio, and area under the curve. In line with International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH), the presented approach was evaluated by its coefficients of determination, detection limits, quantification limits, and relative standard deviations. Similarly, the developed approach was assessed for whiteness, greenness, and sustainability using five assessment tools, including National Environmental Method Index, Eco-Scale Assessment, Complementary Green Analytical Procedure Index, Analytical Greenness Metric, and RGB12, offering promising results. Owing to the satisfactory analytical performance, besides the sustainability, affordability, simplicity, and cost efficiency of the presented methods, their application for quality control and in situ analysis in minimal-infrastructure laboratories increases, increasing the surveillance potential.

A Green-and-White Integrative Analytical Strategy Combining Univariate and Chemometric Techniques for Quantifying Recently Approved Multi-Drug Eye Solution and Potentially Cancer-Causing Impurities: Application to the Aqueous Humor.

Drug impurities are now seen as a major threat to the production of pharmaceuticals around the world and a major part of the global contamination problem, especially when it comes to carcinogenic impurities. We present the first spectrophotometric strategy based on a combination of univariate and multivariate methods as impurity profiling methods for the estimation of lignocaine (LIG) and fluorescein (FLS) with their carcinogenic impurities: 2,6-xylidine (XYL) and benzene-1,3-diol (BZD). The data processing strategy depends on overcoming unresolved bands by employing five affordable, accurate, selective, and sensitive methods. The methods applied were a direct UV univariate spectrophotometric analysis (D0) and four multivariate chemometric methods, including classical least squares (CLS), principal component regression (PCR), partial least squares (PLS), and genetic algorithm (GA-PLS). FLS analysis (1-16 μg/mL) was performed using the D0 method at 478 nm; then, the application of the ratio subtraction method (RSM) allowed the removal of interference caused by the FLS spectrum. From the resulting ratio spectra, LIG, XYL, and BZD can be efficiently determined by chemometrics. The calibration set was carefully selected at five concentration levels using a partial factorial training design, resulting in 25 mixtures with central levels of 160, 40, and 3 μg/mL for LIG, XYL, and BZD, respectively. Another 13 samples were applied to validate the predictive ability. The statistical parameters demonstrated exceptional recoveries and smaller prediction errors, confirming the experimental model's predictive power. The proposed approach was effectively tested using newly FDA-approved LIG and FLS pharmaceutical preparation and aqueous humor. Additionally, it was effectively assessed for whiteness, greenness, and sustainability using five assessment tools. With its remarkable analytical performance, sustainability, affordability, simplicity, and cost-efficiency, the proposed strategy is an indispensable tool for quality control and in situ analysis in little-equipped laboratories, increasing the proposed approach's surveillance ability.

A deep dive into historical Ames study data for N-nitrosamine compounds

Mutagenicity data is a core component of the safety assessment data required by regulatory agencies for acceptance of new drug compounds, with the OECD-471 bacterial reverse mutation (Ames) assay most widely used as a primary screen to assess drug impurities for potential mutagenic risk. N-Nitrosamines are highly potent mutagenic carcinogens in rodent bioassays and their recent detection as impurities in pharmaceutical products has sparked increased interest in their safety assessment. Previous literature reports indicated that the Ames test might not be sensitive enough to detect the mutagenic potential of N-nitrosamines in order to accurately predict a risk of carcinogenicity. To explore this hypothesis, public Ames and rodent carcinogenicity data pertaining to the N-nitrosamine class of compounds was collated for analysis. Here we present how variations to the OECD 471-compliant Ames test, including strain, metabolic activation, solvent type and pre-incubation/plate incorporation methods, may impact the predictive performance for carcinogenicity. An understanding of optimal conditions for testing of N-nitrosamines may improve both the accuracy and confidence in the ability of the Ames test to identify potential carcinogens.

Investigation of the GnRH antagonist degarelix isomerization in biological matrices.

One of the main objectives of peptide drug design is the improvement of peptide pharmacokinetics with maintaining biological activity, which can be achieved by the complex modifications of the primary structure of the peptides. However, these changes often lead to the formation of peculiar impurities in the peptide drugs and their metabolites, which require the development of advanced analytical methods to properly assess their content. Here, we investigated the degradation of the potent long-acting GnRH antagonist degarelix in various biologic media by the tailor-made HPLC method, which allows precise determination of 5-Aph(Hyd)-degarelix isomer, an impurity found in the degarelix active pharmaceutical ingredient (API) during its manufacturing. Unexpectedly, we discovered a rapid and irreversible conversion of degarelix API into the corresponding hydantoin isomer in serum, suggesting that this impurity can be also a potential drug metabolite in vivo. This finding underlines the importance of the development of more accurate and performing analytical techniques to correctly characterize the chemical composition of the manufactured drugs and their behavior under physiological conditions.

Purification and Concentration of Minor Impurity in the Bulk Drug by Step-Gradient Twin-Column Recycling Chromatography

Purification and Concentration of Minor Impurity in the Bulk Drug by Step-Gradient Twin-Column Recycling Chromatography

Confined Target-Triggered Hot Spots for In Situ SERS Analysis of Intranuclear Genotoxic Markers.

The γH2AX is a type of confined target in nuclei which is highly expressed around the damaged DNA during genotoxicity and has therefore been identified as a marker of genotoxicity. Convenient and intuitive in situ real-time detection of γH2AX is crucial for an accurate assessment of genotoxicity. Selective and nondestructive surface-enhanced Raman spectroscopy (SERS) is suitable to achieve this goal. However, the detection of substances in the nucleus by SERS is still limited due to the contradiction of probes between the nuclei entry efficiency and signal enhancement. This study utilized the characteristics of γH2AX as a confined target and constructed a γH2AX immunosensor based on gold nanoprobes with a small size (15 nm), which was modified with the TAT nuclear targeting peptide to ensure high nuclei entry efficiency. Once DNA damage was induced, the local overexpression of γH2AX further recruited the probe through immune recognition, so that hot spots could be assembled in situ to generate strong Raman signals, which were applied to evaluate the genotoxicity of drug impurities. This study proposed a novel SERS detection strategy, characterized by confined target-induced size conversion and hot spot formation, for in situ real-time analysis of intranuclear targets at the single-living-cell level, which intelligently simplified the structure of SERS probes and the operation process.

Structural Elucidation of Novel Degradation Impurity and Development, Validation of a Single HPLC Method for all Putative Impurities of Clobetasol Propionate in a Foam Drug Product.

Clobetasol Propionate is a highly strong corticosteroid that is used in a variety of topical medication formulations, including foam, ointment, lotion, spray and shampoo; with a dosage strength of 0.05% (w/w). The goal of this research was to identify and characterize a substantial unknown impurity (UK) detected during the stability testing of a Clobetasol Propionate foam pharmaceutical product in accelerated conditions (40°C and 75% relative humidity). Developing a single, robust and accurate HPLC method that is LC-MS compatible for quantifying all 14 potential Clobetasol Propionate impurities in therapeutic drugs is another goal. Preparative column chromatography was used to separate the impurity, and spectroscopic techniques like IR, NMR and MS were used to characterize its structure. The structure of isolated UK was effectively characterized and defined using spectroscopic data evaluation. The chromatographic method has also been validated according to the International Conference on Hominization's Q (2) quality guidelines. The isolated and characterized impurity had the same equivalence as the impurity found during stability testing. Precision, accuracy, linearity, robustness and ruggedness are all met in the method validation data.

DNA Alkylation Damage by Nitrosamines and Relevant DNA Repair Pathways

Nitrosamines occur widespread in food, drinking water, cosmetics, as well as tobacco smoke and can arise endogenously. More recently, nitrosamines have been detected as impurities in various drugs. This is of particular concern as nitrosamines are alkylating agents that are genotoxic and carcinogenic. We first summarize the current knowledge on the different sources and chemical nature of alkylating agents with a focus on relevant nitrosamines. Subsequently, we present the major DNA alkylation adducts induced by nitrosamines upon their metabolic activation by CYP450 monooxygenases. We then describe the DNA repair pathways engaged by the various DNA alkylation adducts, which include base excision repair, direct damage reversal by MGMT and ALKBH, as well as nucleotide excision repair. Their roles in the protection against the genotoxic and carcinogenic effects of nitrosamines are highlighted. Finally, we address DNA translesion synthesis as a DNA damage tolerance mechanism relevant to DNA alkylation adducts.