LC-UV Method Research Articles

Pharmacokinetics, tissue distribution and excretion study of trans-resveratrol-3-O-glucoside and its two metabolites in rats

BackgroundTrans-resveratrol-3-O-glucoside (TRG), isolated from the Chinese traditional herbal medicine Huzhang, has been shown to have a wide range of pharmacological benefits. PurposeThe aim of this study is to investigate the pharmacokinetics, tissue distribution and excretion of TRG and its metabolites, (TRN (trans-resveratrol-3-O-glucuronide) and TR (trans-resveratrol)), following a single intragastric (i.g.) administration of TRG in rats. Study designTo evaluate the pharmacokinetic properties of TRG, TRN and TR, groups of rats were administrated a single i.g. dose of either 75, 150 or 300 mg/kg TRG. The absolute bioavailability of TRG was estimated from the ratios of AUC0-∞ values for oral and intravenous administration. Tissue distributions of TRG, TRN and TR in rats were investigated following a single i.g. administration to four groups at 150 mg/kg dosage of TRG. For urinary, fecal and biliary excretion study, TRG, TRN and TR excretions were recovered from a group of rats administered a single i.g. dose of 150 mg/kg TRG. MethodsThe levels of TRG, TRN and TR in plasma, tissues, bile, urine and feces were measured by a rapid and sensitive LC-UV method. The precision was below 10.0%, and the accuracy was within ±9.9% for TRG, TRN and TR. ResultsThe concentrations of TRN were markedly higher than those of TRG and TR in plasma, urine and bile. TRG, TRN and TR showed linear dynamics in dose range of 75–300 mg/kg TRG. TRG had poor absolute bioavailability in rats. The major distribution tissues of TRG, TRN, and TR in rats were in the digestive tract. TRG, TRN and TR were all eliminated from tissues quickly. TRG was mostly excreted via the renal route in the form of TRN, which accounted for 52.8% of the administered dose up to 72 h. ConclusionFollowing a single i.g. administration to rats TRG was easily absorbed and rapidly converted to the metabolites TR and TRN. These metabolites were found to be mainly excreted by the kidneys.

Determination of lansoprazole, 5-hydroxylansoprazole, and lansoprazole sulfone in human plasma for CYP2C19 and CYP3A4 phenotyping

A simple and sensitive liquid chromatography method with absorbance or mass spectrometry detection was developed and validated for the determination of lansoprazole, lansoprazole sulfone, and 5-hydroxylansorpazole in human serum with omeprazole as an internal standard. Analytes were, after an extraction step with a mixture of isopropyl alcohol: dichloromethane (2:8, v/v), separated in a gradient elution (acetonitrile: 20 mM ammonium formate) and detected at 280 and 300 nm or by monitoring selective reactions in a triple quadrupole mass analyzer. The limits of detection were, for all analytes, below 2 ng/mL and 3 pg/mL in the LC UV and LC MS method, respectively. The combined linear dynamic range exceeded 5 orders of magnitude. The method was successfully applied in the assessment of CYP2C19 and CYP3A4 metabolic phenotypes in ST-elevated myocardial infarction patients receiving novel anticoagulant treatment.

LC-UV method to assay raloxifene hydrochloride in rat plasma and its application to a pharmacokinetic study

A specific, precise, and accurate LC-UV method was developed and validated to assay raloxifene hydrochloride in rat plasma. Raloxifene was analyzed after liquid-liquid extraction and quantified by reversed phase liquid chromatography (C18 column) using acetonitrile and ammonium acetate buffer 0.05 M (pH 4.0) as mobile phase at a flow rate of 1 mL.min-1 and UV detection at 287 nm. Retention times of raloxifene and internal standard (dexamethasone) were approximately 11 min and 14 min, respectively. Linearity was checked for a concentration range between 25 ng.mL-1 and 1000 ng.mL-1. Intra- and inter-day precision had relative standard deviation lower than 10% and 15%, respectively. Recovery from plasma was higher than 90%. Accuracy values were 98.21%, 99.70%, and 102.70% for lower, medium, and upper limits of quantification, respectively. Limit of quantification was 25 ng.mL-1. Drug stability was analyzed at room temperature using plasma kept in a freezer at -80 °C for 45 days after processing for 6 h and three freeze-thaw cycles. The advantages of the method developed include stability under different conditions and low limit of quantification. Its applicability was confirmed by the analysis of raloxifene levels in plasma samples in a designed pharmacokinetic study in rats after intravenous administration (5 mg.kg-1).

Quantification of Sambucus nigra (Adoxaceae) Markers Related to Tincture Stability

Stability tests are essential to assuring herbal derivative quality, especially because of the complexity of the herbal matrix. To monitor the stability of Sambucus nigra L. flower tincture, a practical liquid chromatography (LC)-UV method was developed and validated. Rutin, the flower's pharmacopeial marker, in addition to other markers, isoquercitrin and quercetin, were quantified. The last two represent the degradation products of glycosylated flavonoids. In addition, other chromatographic peaks exhibiting typical flavonoid UV absorption profiles (total flavonoids) were also quantified and expressed in rutin equivalents. The method was developed with a reverse phase C18 column, using a gradient mobile phase at 0.7 mL min -1 at 30°C. The herbal drug and tincture obtained by percolation at 60 °C with ethanol 25% (v/v) were submitted to accelerated (40°C/75% RH, 2 months) and long duration (15–30°C, 6 months) studies. The LC-UV method was linear in the ranges of 1–200 μg mL-1 (rutin) and 1–100 μg mL-1 (isoquercitrin and quercetin), without interference of herbal matrix, and was precise (RSD ≤ 2.0% for intra and interday precision), selective, and robust (changes in mobile phase flow, pH and temperature). The tincture revealed the presence of quercetin, which was absent in the herbal drug, likely due to the hydrolysis process. After 2 months under accelerated study, the total flavonoids in the tincture decreased by approximately 20%, and after 6 months at room temperature, they decreased by approximately 30%. These results indicate the thermolability of the S. nigra tincture and the importance of monitoring phytomedicine stability.

Determination of chemical stability of sitagliptin by LC-UV, LC-MS and FT-IR methods

Sitagliptin was stored at high temperature/high humidity, dry hot air, UV/VIS light and different pH. Then, a selective LC-UV method was developed for determination of sitagliptin in the presence of degradation products and for estimation of degradation kinetics. Because parent drugs can react with excipients in final pharmaceutical formulations, stability of sitagliptin was also examined in the presence of excipients of different reactivity, using FT-IR and LC-UV methods. Finally, LC–MS method was used for identification of degradation products of sitagliptin.High degradation of sitagliptin, following the first order kinetics, was observed in strongly acidic, alkaline and oxidative media. The quickest degradation was found in 2 M HCl and 2 M NaOH. In addition, all excipients used in the present study, i.e. fumaric acid, lactose, mannitol and magnesium stearate showed potent interactions with sitagliptin. Some of these interactions were shown without any stress while others were accelerated by high temperature/high humidity and dry hot air, and less by UV/VIS light. Some mechanisms for the observed changes were proposed, i.e. the Michael addition in the presence of fumaric acid and the Maillard reaction in the presence of lactose. In addition, degradation of sitagliptin together with the occurrence of its impurities was stated in a broad range of stress conditions.

Identification, Characterization and High-Performance Liquid Chromatography Quantification for Process-Related Impurities in Abiraterone Acetate Bulk Drug.

During the synthesis of abiraterone acetate bulk drug in some laboratory batches, two unreported impurities were detected by high-performance liquid chromatography analysis at levels ranging from 0.05 to 0.10% according to the United States Pharmacopeia method. The structures of two impurities were characterized and confirmed by NMR and MS, which were proposed to be [3β-acetoxy-16-(3β-acetoxy-androsta-5,16-dien-17-yl)-17-(3-pyridyl)-androsta-5,16-di-ene] and [3β-acetoxy-16-(3β-acetoxy-androsta-5,16-dien-17-yl)-17-androsta-5,16-di-ene]. It was proved that these impurities come into being during the preparation process of penultimate intermediate (abiraterone). The newly developed LC-UV method was used to monitor the impurity profile in the penultimate intermediate (abiraterone), which was validated by its satisfactory specificity, precision, accuracy and sensitivity. The probable origin of the impurity was also discussed.

Development and Validation of a Fast Reversed Phase Liquid Chromatographic Method for the Analysis of Ethionamide in Dosage Forms

Background: Ethionamide (ETA) is widely used as one of the agents for the treatment of multidrug resistant tuberculosis. Although quality control is an important issue, a fast LC-UV method for the assay and impurity determination of ETA was lacking. So, the aim of this study was to develop such a method to evaluate drug products and follow up dissolution tests of ETA tablets. Methods: Chromatographic separation was achieved using a Hypersil BDS C18 (150 mm×4.6 mm, 3 µm) column kept at 30 °C. The mobile phase consisted of 300 mL of acetonitrile, 0.14 g of NH4H2PO4 and 700 mL of water pumped at a flow rate of 1.0 mL/min. UV detection was performed at 287 nm. The developed LC method was validated according to the ICH guidelines. Results: Validation results show that the developed LC method is specific, linear, sensitive, precise, accurate and robust. Forced degradation studies revealed that the generated degradation products did not interfere with ETA and known impurities, thus proving the specificity of the developed LC method for the assay of ETA tablets and quantification of impurities. Conclusion: A robust, selective, sensitive and fast LC method has been developed and validated for analysis of ETA and its main impurities in tablets. Keywords: Ethionamide, impurities, assay, method development, validation, liquid chromatography.

Development of a sensitive and quantitative capillary LC-UV method to study the uptake of pharmaceuticals in zebrafish brain.

The present study explores the potential of 10-day-old zebrafish (Danio rerio) as a predictive blood-brain-barrier model using a set of 7 pharmaceutical agents. For this purpose, zebrafish were incubated with each of these 7 drugs separately via the route of immersion and the concentration reaching the brain was determined by applying a brain extraction procedure allowing isolation of the intact brain from the head of the zebrafish larvae. Sample analysis was performed utilizing capillary ultra-high performance liquid chromatography (cap-UHPLC) on a Pepmap RSLC C18 capillary column (150mm × 300μm, dp = 2μm) coupled to a variable wavelength UV detector. Gradient separation was performed in 28min at a flow rate of 5μL/min and the optimal injection volume was determined to be 1μL. The brain extraction procedure was established for the zebrafish strain TG898 exhibiting red fluorescence of the brain, allowing control of the integrity of the extracted parts. Quantitative experiments carried out on pooled samples of six zebrafish (n = 6) demonstrated the selective semipermeable nature of the blood-brain barrier after incubating the zebrafish at the maximum tolerated concentration for the investigated pharmaceuticals. The obtained brain-to-trunk ratios ranged between 0.3 for the most excluded compound and 1.2 for the pharmaceutical agent being most accumulated in the brain of the fish. Graphical abstract Workflow of brain extraction to study the uptake of pharmaceuticals in the brain of zebrafish larvae.

Exhaled breath condensate as an alternative sample for drug monitoring.

Exhaled breath condensate as an alternative sample for drug monitoring.

Troxerutin, a mixture of O-hydroxyethyl derivatives of the natural flavonoid rutin: Chemical stability and analytical aspects

Troxerutin (TRX) is a mixture of semisynthetic hydroxyethylrutosides (Hers) arising from hydroxyethylation of rutin, a natural occurring flavonoid. TRX is commonly used for its anti-oxidant and anti-inflammatory properties in chronic venous insufficiency and other vascular disorders. In recent studies, the protective effects of TRX in Alzheimer’s disease, colon carcinogenesis and hepatocellular carcinoma are emerged. However, the chemical stability of TRX has never been studied. Hence, the aims of the work were to study the TRX chemical stability through a forced degradation study and to develop and validate a new stability indicating LC-UV method for determination of TRX. In order to perform the study, TRX stability was tested in various stress conditions analysing the degradation samples by LC–MS. Three degradation products (DPs; D1, D2 and D3, 3′,4′,7-Tri-O-(β-hydroxyethyl)quercetin, 3′,4′,5,7-Tetra-O-(β-hydroxyethyl)quercetin and 3′,4′-Di-O-(β-hydroxyethyl)quercetin respectively) arising from degradation in acidic conditions were identified and synthesized: among them, D1 resulted the stability indicator for hydrolytic degradation. Furthermore, a stability-indicating LC-UV method for simultaneous determination of triHer (3′,4′,7-Tri-O-(β-hydroxyethyl)rutin, the principal component of the mixture) and D1 was developed and validated. The LC-UV method consisted in a gradient elution on a Phenomenex Kinetex EVO C18 (150 × 3 mm, 5 μm) with acetonitrile and ammonium bicarbonate buffer (10 mM, pH 9.2). The method was linear for triHer (20–60 μg mL−1) and D1 (5.1–35 μg mL−1). The intraday and interday precision were determined and expressed as RSDs: all the values were ≤ 2% for both triHer and D1. The method demonstrated also to be accurate and robust and the average recoveries were 98.8 and 97.9% for triHer and D1, respectively. Moreover, the method resulted selective and specific for all of the components present in the degradation pattern of TRX (diHer (3′,4′-Di-O-(β-hydroxyethyl)rutin), triHer, tetraHer (3′,4′,5,7-Tetra-O-(β-hydroxyethyl)rutin), D3, D1 and D2) and it was successfully applied for the stability studies of both drug substances and drug products.

A Metabolomic Approach Applied to a Liquid Chromatography Coupled to High-Resolution Tandem Mass Spectrometry Method (HPLC-ESI-HRMS/MS): Towards the Comprehensive Evaluation of the Chemical Composition of Cannabis Medicinal Extracts.

Cannabis sativa L. is a powerful medicinal plant and its use has recently increased for the treatment of several pathologies. Nonetheless, side effects, like dizziness and hallucinations, and long-term effects concerning memory and cognition, can occur. Most alarming is the lack of a standardised procedure to extract medicinal cannabis. Indeed, each galenical preparation has an unknown chemical composition in terms of cannabinoids and other active principles that depends on the extraction procedure. This study aims to highlight the main differences in the chemical composition of Bediol® extracts when the extraction is carried out with either ethyl alcohol or olive oil for various times (0, 60, 120 and 180min for ethyl alcohol, and 0, 60, 90 and 120min for olive oil). Cannabis medicinal extracts (CMEs) were analysed by liquid chromatography coupled to high-resolution tandem mass spectrometry (LC-MS/MS) using an untargeted metabolomics approach. The data sets were processed by unsupervised multivariate analysis. Our results suggested that the main difference lies in the ratio of acid to decarboxylated cannabinoids, which dramatically influences the pharmacological activity of CMEs. Minor cannabinoids, alkaloids, and amino acids contributing to this difference are also discussed. The main cannabinoids were quantified in each extract applying a recently validated LC-MS and LC-UV method. Notwithstanding the use of a standardised starting plant material, great changes are caused by different extraction procedures. The metabolomics approach is a useful tool for the evaluation of the chemical composition of cannabis extracts. Copyright © 2017 John Wiley & Sons, Ltd.

Development and validation of a LC-UV Method Applied to the Quality Control of Ursodeoxycholic Acid in Raw Material and Pharmaceutical Formulations

Development and validation of a LC-UV Method Applied to the Quality Control of Ursodeoxycholic Acid in Raw Material and Pharmaceutical Formulations

Development and Validation of a Simple LC-UV Method to Assay Doxazosin in Polymeric Nanocapsules and Tablets

Development and Validation of a Simple LC-UV Method to Assay Doxazosin in Polymeric Nanocapsules and Tablets

Quantification of piritramide in human colostrum.

In our university hospital (UZBrussel), one of the options to control post-operative pain after a Caesarean section under general anaesthesia is to administer piritramide by patient-controlled intravenous analgesia (PCIA). As no information is available about the possible transfer of this synthetic narcotic analgesic into breastmilk, women are frequently advised not to breastfeed their newborn. A sensitive liquid chromatographic (LC) method coupled with UV detection will therefore be developed and validated for the quantification of piritramide in colostrum samples to evaluate the presence of the analgesic in the first milk. The method included the isolation and concentration of piritramide from colostrum using protein precipitation and solid-phase extraction (SPE) using a mixed-mode cation exchange sorbent. Subsequently, the extracted samples were analysed on a microbore C18 column (1 mm id) and a mobile phase consisting of 15 mm ammonium hydroxide in methanol/tetrahydrofuran/water 50 : 10 : 40 V/V/V. As colostrum contains a high amount of proteins, mixed-mode cation exchange SPE was preceded by a 1 : 2 dilution and protein precipitation with phosphoric acid followed by double centrifugation of the samples. The reversed-phase LC-UV method used a mobile phase at alkaline pH to obtain a selective method for piritramide and the internal standard pipamperone. After investigating the validation characteristics (linearity, accuracy, precision and stability), samples from ten patients who had received piritramide via PCIA during the first 48 h post-partum were analysed. To the best of our knowledge, this is the first method described for the quantification of the synthetic narcotic analgesic piritramide in colostrum samples. The obtained results suggest that after the administration of this opioid by PCIA to nursing mothers low concentrations of piritramide can be found in the first milk, but are mostly below the limit of quantification of 30 ng/mL.

Quantitative determination of salbutamol sulfate impurities using achiral supercritical fluid chromatography

In the last years, supercritical fluid chromatography has largely been acknowledged as a singular and performing technique in the field of separation sciences. Recent studies highlighted the interest of SFC for the quality control of pharmaceuticals, especially in the case of the determination of the active pharmaceutical ingredient (API). Nevertheless, quality control requires also the determination of impurities. The objectives of the present work were to (i) demonstrate the interest of SFC as a reference technique for the determination of impurities in salbutamol sulfate API and (ii) to propose an alternative to a reference HPLC method from the European Pharmacopeia (EP) involving ion-pairing reagent. Firstly, a screening was carried out to select the most adequate and selective stationary phase. Secondly, in the context of robust optimization strategy, the method was developed using design space methodology. The separation of salbutamol sulfate and related impurities was achieved in 7min, which is seven times faster than the LC-UV method proposed by European Pharmacopeia (total run time of 50min). Finally, full validation using accuracy profile approach was successfully achieved for the determination of impurities B, D, F and G in salbutamol sulfate raw material. The validated dosing range covered 50 to 150% of the targeted concentration (corresponding to 0.3% concentration level), LODs close to 0.5μg/mL were estimated. The SFC method proposed in this study could be presented as a suitable fast alternative to EP LC method for the quantitative determination of salbutamol impurities.

Rapid analysis of N-methylpyrrolidine in cefepime with thermal desorption ion mobility spectrometry

N-methyl-pyrrolidine (NMP) a potential impurity in the cephalosporin antibiotic cefepime is analysed using a rapid thermal desorption – ion mobility spectrometry (TD-IMS) method. The thermal desorption approach is shown to be capable of rapidly extracting NMP from the cefepime at 80 °C without causing thermal degradation of the cefepime. The ion mobility method has an analysis time of 1 min and demonstrates good linearity over a range from 0.3–3.0 μg ml−1 of NMP, with limits of detection and quantification of 0.056 and 0.1875 μg ml−1 respectively. The developed method was applied to the analysis of a cefepime sample and determined that NMP was present in a cefepime sample at a level of 0.0376 % with a percentage relative standard deviation (n = 6) of 3.2 %. This was compared with a LC-UV method which was in close agreement measuring NMP at 0.0384 % in the cefepime sample with a percentage RSD (n = 6) of 5.7 %. These results show that the TD-IMS method gives comparable data to the established LC methods and demonstrates the potential of TD-IMS for rapid measurement of volatile compounds in pharmaceutical matrices.

Chemical Isotope Labeling LC-MS for High Coverage and Quantitative Profiling of the Hydroxyl Submetabolome in Metabolomics.

A key step in metabolomics is to perform accurate relative quantification of the metabolomes in comparative samples with high coverage. Hydroxyl-containing metabolites are an important class of the metabolome with diverse structures and physical/chemical properties; however, many of them are difficult to detect with high sensitivity. We present a high-performance chemical isotope labeling liquid chromatography mass spectrometry (LC-MS) technique for in-depth profiling of the hydroxyl submetabolome, which involves the use of acidic liquid-liquid extraction to enrich hydroxyl metabolites into ethyl acetate from an aqueous sample. After drying and then redissolving in acetonitrile, the metabolite extract is labeled using a base-activated 12C- or 13C-dansylation reaction. A fast step-gradient LC-UV method is used to determine the total concentration of labeled metabolites. On the basis of the concentration information, a 12C-labeled individual sample is mixed with an equal mole amount of a 13C-labeled pool or control for relative metabolite quantification. The 12C-/13C-labeled mixtures are individually analyzed by LC-MS, and the resultant peak pairs of labeled metabolites in MS are measured for relative quantification and metabolite identification. A standard library of 85 hydroxyl compounds containing MS, retention time, and MS/MS information was constructed for positive metabolite identification based on matches of two or all three of these parameters with those of an unknown. Using human urine as an example, we analyzed samples of 1:1 12C-/13C-labeled urine in triplicate with triplicate runs per sample and detected an average of 3759 ± 45 peak pairs or metabolites per run and 3538 ± 71 pairs per sample with 3093 pairs in common (n = 9). Out of the 3093 peak pairs, 2304 pairs (75%) could be positively or putatively identified based on metabolome database searches, including 20 pairs positively identified using the dansylated hydroxyl standards library. The majority of detected metabolites were those containing hydroxyl groups. This technique opens a new avenue for the detailed characterization of the hydroxyl submetabolome in metabolomics research.

A sensitive capillary LC-UV method for the simultaneous analysis of olanzapine, chlorpromazine and their FMO-mediated N-oxidation products in brain microdialysates

A specific and sensitive capillary liquid chromatography-ultraviolet detection (cap-LC-UV) method in combination with a micro-extraction by packed sorbent (MEPS) sample clean-up procedure has been developed and validated for the simultaneous analysis of chlorpromazine, olanzapine and their flavin-containing monooxygenase (FMO) mediated N-oxides in rat brain microdialysates. Chromatographic separation was obtained on an Acclaim Pepmap RP C18 column with an ID of 300µm. An injection volume of 20µL was used to inject the largely aqueous samples and was shown to have no influence on the obtained peak shape of the compounds of interest. Optimal conditions for MEPS extraction were obtained on a mixed-mode M1 (80% C8, 20% SCX) cartridge after diluting microdialysate samples with phosphate buffer pH 2.5 (1:3 v/v). The method was validated and lower limits of quantification (LLOQ) were determined at 0.5nM for all compounds. Linearity was demonstrated between the LLOQ and 1µM for all compounds (R2>0.995). MEPS recoveries were between 92% and 98%, with intra- and interday variabilities below 15%. The applicability of the developed method was successfully demonstrated by analysing rat brain microdialysates. The capillary LC-UV method in combination with MEPS sample treatment provides a simple, sensitive method to quantify all compounds of interest in 45min and can be applied for routine therapeutic monitoring and pharmacokinetic studies of olanzapine, chlorpromazine and their respective N-oxides.

Development and evaluation of a liquid chromatography–mass spectrometry method for rapid, accurate quantitation of malondialdehyde in human plasma

Malondialdhyde (MDA) is a commonly used marker of lipid peroxidation in oxidative stress. To provide a sensitive analytical method that is compatible with high throughput, we developed a multiple reaction monitoring-mass spectrometry (MRM-MS) approach using 3-nitrophenylhydrazine chemical derivatization, isotope-labeling, and liquid chromatography (LC) with electrospray ionization (ESI)-tandem mass spectrometry assay to accurately quantify MDA in human plasma. A stable isotope-labeled internal standard was used to compensate for ESI matrix effects. The assay is linear (R(2)=0.9999) over a 20,000-fold concentration range with a lower limit of quantitation of 30fmol (on-column). Intra- and inter-run coefficients of variation (CVs) were <2% and ∼10% respectively. The derivative was stable for >36h at 5°C. Standards spiked into plasma had recoveries of 92-98%. When compared to a common LC-UV method, the LC-MS method found near-identical MDA concentrations. A pilot project to quantify MDA in patient plasma samples (n=26) in a study of major depressive disorder with winter-type seasonal pattern (MDD-s) confirmed known associations between MDA concentrations and obesity (p<0.02). The LC-MS method provides high sensitivity and high reproducibility for quantifying MDA in human plasma. The simple sample preparation and rapid analysis time (5x faster than LC-UV) offers high throughput for large-scale clinical applications.

Characterization and comparability of stress-induced oxidation and deamidation on vulnerable sites of etanercept products

An etanercept biosimilar, TuNEX(®), was compared to the innovator drug, Enbrel(®), for its reaction to stress-induced oxidation and deamidation, which may affect drug efficacy. A tryptic peptide map of both etanercept products was generated by liquid chromatography (LC) using mass spectrometry (MS) and ultraviolet (UV) spectrophotometry detection methods. The sequence of each modified or non-modified peptide peak was assigned based on accurate measurement of the mass of the protein and analysis utilizing tandem MS. Similar profiles of intrinsic oxidation on methionine (M) and deamidation on asparagine (N) were obtained for the two products, regardless of a two-amino acid (AA) residue variance in the heavy chain (Fc) between them. The level of oxidative stress exerted by tert-butyl hydroperoxide (tBHP), and alkaline stress exerted by a pH 10.4 solution, was examined using an LC-UV method. The results indicated that TuNEX(®) demonstrated a similar stress-induced modification profile compared to that of Enbrel(®). For both products, oxidative stress increased the oxidation from an intrinsically low (0-6.9%) to moderate or high (42-100%) level for almost all M residues (M30, M174, M187, M223, M272, and M448); alkaline stress increased the deamidation level of N404 from a low (0.0 or 1.7%) to moderate (19-26%) level. Based the results of a cell-based bioactivity assay, TuNEX(®) also exhibited a similar level of bioactivity as Enbrel(®) in unstressed, oxidative-stressed, or alkaline-stressed conditions. The bioactivity of both products remained unaltered by oxidative stress but was reduced by alkali stress. In conclusion, our data indicated that TuNEX(®) exhibits a similar chemical stress profile as that of Enbrel(®) in terms of oxidation and deamidation as well as bioactivity.