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Acta Chromatographica
Authors: S. Hiriyanna Hiriyanna, K. Basavaiah, P. S. Goud Goud, V. Dhayanithi, K. Raju, and H. Pati Pati

Summary

Studies of the degradation of olanzapine bulk drug under hydrolytic (acidic and alkaline), oxidising, and photolytic conditions are reported in this paper. Olanzapine is almost completely stable under photolytic and hydrolytic (acidic and alkaline) conditions. The major degradation products formed when olanzapine bulk drug was exposed to oxidative stress conditions were isolated by preparative reversed-phase high-performance liquid chromatography and characterized by FTIR, LC-MS-MS, and 1H, 13C, and DEPT NMR. On the basis of results from spectroscopy the degradation products were characterized as 10-hydroxy-2-methyl-5,10-dihydro-4H-benzo[b]thieno [2,3-e][1,4]diazepin-4-one, 2-methyl-5,10-dihydro-4H-benzo[b]thieno[2,3-e][1,4]diazepin-4-one, and 2-methyl-10-(2-methyl-10H-benzo[b]thieno[2,3-e][1,4] diazepin-4-yloxy)-5,10-dihydro-4H-benzo[b]thieno[2,3-e]diazepin-4-one. Identification, isolation, and characterization of these oxidative degradation products are discussed in detail.

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Abstract  

The dynamics of redox related elements (Fe, Co, Zn, and Se) were studied using instrumental neutron activation analysis as a function of rat age in the range of 4 to 16 weeks. Activity levels of glutathione peroxidase (GSH-Px), thiobarbituric acid reactive substance (TBARS) were assayed, and hydrogen peroxide (H2O2) concentrations were measured for the same liver homogenates using an X-band ESR spectrometer. The oxidative stress, the aging effect, and the mineral valance are discussed.

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degradation. The oxidative stress conditions were optimized from lower hydrogen peroxide concentration (0.3%) to higher concentration (15%). The photolytic and thermal stress conditions were set as same for both the drug substances. For AT, acid, base, and

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A sensitive and precise high-performance thin-layer chromatographic (HPTLC) method has been developed for the simultaneous estimation of clozapine and aripiprazole in combination. The method employed HPTLC aluminum plates pre-coated with silica gel 60 F254 as the stationary phase, while the solvent system was toluene‒methanol‒ethyl acetate‒ammonia (6.5:2.5:1:0.1, v/v). The R F values were observed to be 0.43 and 0.60 for clozapine and aripiprazole, respectively. Densitometric analysis was carried out in absorbance mode at 218 nm. The method was linear in the range of 200–1600 ng per band for clozapine and 100-800 ng per band for aripiprazole. The stress degradation study was performed, and it was found that clozapine was susceptible to acid hydrolysis, base hydrolysis, and photolytic degradation study. Aripiprazole was susceptible to oxidative stress degradation study. The method was validated and applied successfully for the estimation of both drugs in the synthetic mixture.

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oxidative stress and age-related diseases , BioMed Res. Int. 2019 ( 2019 ), article ID 8748253, 16 pages. [10] R.J. Thoppil , A. Bishayee

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Abstract  

Free radicals and oxidative stress are the primary causes of several chronic diseases such as cancer and heart disease. Quercetin is a natural compound with potent antioxidant activity. We have prepared and evaluated technetium-99m (99mTc)-labeled quercetin as a potential radical scavenging radiotracer. A 99mTc-quercetin complex was prepared using quercetin, SnCl2 and Na99mTcO4 in a buffered solution over 30 min. The participation coefficient was measured in octanol and queues solutions. The stability was determined in phosphate buffered saline and serum. The biodistribution in normal mice was evaluated at 0.5, 2, 6 and 24 h post-injection. The radiochemical purity (>99%) was determined by thin layer chromatography (TLC) in normal saline solution as the mobile phase. It has a log P of 0.204. It was mainly cleared by the kidneys and showed negligible brain uptake at four time points measured post-injection. The pharmacological properties of quercetin, mainly its free radical scavenging, may potentially cat as a radiopharmaceutical agent for radical-targeted imaging of tissue with high levels of reactive oxygen species.

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The aim of this study was to investigate the role of (+)-catechin and (−)-epicatechin in the molecular processes of formation of red heartwood, a structural and color anomaly of living beech which causes substantial economic loss. The causes of the formation of red heartwood and the molecular carriers and participants are unknown. It has been proven that the activity of phenol oxidizing enzymes (POD, PPO) increases at the color boundary, but the phenolic compounds participating in these reactions, and probably building up the red chromophores are unknown. Catechins play an important role in defense reactions against oxidative stress in plant tissues and are also major phenolic constituents of beech wood. A simple and readily applicable TLC method has been implemented to measure the radial distribution of the concentrations of the two epimers in healthy and discolored beech disks. The reactions at the color boundary could also be tracked by use of this technique. The results show unequivocally the role of the two catechins, and presumably the role of other flavan-3-ols also, in the formation of the red chromophores. By establishing the exact composition of the red chromophores the color stability of red-heartwood material and its industrial utilization could also be enhanced.

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A stability-indicating capillary electrophoresis method coupled to a diode array detector (DAD) was developed and validated for the simultaneous determination of emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF) in combined tablets. This proposed method utilized a fused silica capillary (effective length, 62 cm; internal diameter [ID], 75 μm) and a background electrolyte (BGE) consisting of phosphate solution (pH 9.5, 50 mM). The separation was achieved at a voltage of 25 kV and a temperature of 21 °C using paracetamol as an internal standard. The described method was linear over the range of 5–200 μg/mL for both drugs (r = 0.9992). Intra- and inter-day relative standard deviation (RSD) (n = 9) was 0.41%. The limits of detection for FTC and TDF were 1.25 and 1.00 μg/mL, respectively. The average percentage recoveries of FTC and TDF from their tablet formulations were 99.66 ± 0.73 and 99.48 ± 0.33, respectively. The two drugs were subjected to thermal, photolytic, hydrolytic, and oxidative stress conditions, and then the stressed samples were analyzed by the proposed method. Degradation products produced as a result of stress studies did not interfere with the detection of FTC and TDF. The assay can thus be considered stability indicating.

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Acta Chromatographica
Authors: Aida Begic, Ana Djuric, Borko Gobeljic, Ivana Stevanovic, Vera Lukic, Ivan Stanojevic, Milica Ninkovic, Luciano Saso, Danilo Vojvodic, and Mirjana Djukic

The aim of our work was to optimize and apply simple high-performance liquid chromatography method with ultraviolet detection (HPLC—UV) for simultaneous determination of reduced (GSH) and oxidized (GSSG) glutathione in biological matrix (specifically, the rat liver tissue was used herein), since the ratio between oxidized and reduced glutathione forms (GSSG—GSH) has been recognized as an important biological marker of oxidatively depleted GSH in oxidative stress (OS)-associated diseases and poisonings. An isocratic chromatographic separation of GSH and GSSG (2.8 min and 6.3 min, respectively) was performed with the mobile phase consisted of sodium perchlorate solution (pH adjusted to 2.8) at flow rate of 1 mL min−1, detection set at 215 nm, and column temperature of 40 °C. The method offers short run time, linearity in the range of 0.01—200 μM concentration for both compounds (R 2 = 1), low limits of detection and quantification (GSH: 0.18 μM and 0.56 μM, GSSG: 0.52 μM and 1.58 μM, respectively), precision, accuracy (bias < 2%), and high reproducibility.

Through suitable sample handling, an overestimation of GSSG was prevented. High recovery (>99%) was achieved. The method was successfully applied for the analysis of GSH and GSSG in liver homogenates of Wistar rats intraperitoneally exposed to cadmium (Cd) (1 mg kg−1 CdCl2/21 days). Regardless of other Cd-mediated hepatotoxicity mechanisms, herein, we have exclusively interpreted/emphasized oxidative GSH depletion.

The presented method is acceptable for a routine analysis of GSH and GSSG in biological matrix, while the calculated ratio GSSG—GSH is considered as a valuable OS marker.

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A simple stability-indicating high-performance liquid chromatography-diode array detection (HPLC-DAD) method has been developed for the simultaneous determination of triamterene (TRI) and xipamide (XIP) in presence of the degradation products generated in studies of forced decomposition. Drugs were subjected to stress by hydrolysis (acidic, alkaline, and neutral), oxidation, photolysis (254 and 365 nm), and dry and wet heat treatments. Degradation occurs under acidic and alkaline conditions (TRI only), oxidative stress (TRI and XIP), and by photolysis (XIP only), but both drugs were stable under other stress conditions investigated. Separation of the two drugs from all the degradant peaks was achieved within 11 min using C8 column (250 × 4.6 mm, 5 μm) and mobile phase consisting of acetonitrile and 0.05 M phosphate buffer adjusted to pH 4 delivered at a flow rate of 1 mL min−1 using gradient elution system. The drugs were quantified at 220 nm using photodiode array detector, based on peak area. Peak homogeneity of the two drugs was checked using diode array detector, and the purity angle was within the purity threshold limit in all of the stressed samples. The calibration graphs for each drug were rectilinear in the range of 0.2–50 and 0.1–20 μg mL−1 for TRI and XIP, respectively. The method was validated in compliance with International Conference on Harmonization (ICH) guidelines; in terms of linearity, accuracy, precision, robustness, limit of detection, and limit of quantitation. The proposed method was successfully applied for the determination of the investigated drugs in their tablet without interference from excipients with acceptable accuracy and precision; the label claim percentages were 100.23 ± 0.70% and 100.75 ± 1.11% for TRI and XIP, respectively.

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