Potential Degradation Products Research Articles

A Simple Validated LC-UV Method for the Simultaneous Determination of Brimonidine and Brinzolamide in the Presence of Brinzolamide's Degradation Product (Major Metabolite) in Rabbit Aqueous Humor.

A sensitive, specific, reliable and low-cost LC-UV method has been developed and validated for simultaneous quantification of brimonidine tartrate (BM) and brinzolamide (BZ) in rabbit aqueous humor (AH) in the presence of N-desethyl-brinzolamide (NDBZ); BZ is a major degradation product, and it is also considered to be its major metabolite. Dorzolamide hydrochloride (DZ) was used as an internal standard (IS). The analytes were extracted from rabbit AH samples by a simple pre-treatment utilizing ZnSO4.7H2O as a deproteinizing agent. The analytes were separated on a cyanopropyl Waters column (4.6 × 200mm, 5μm) with an isocratic mobile phase consisting of 25mM ammonium acetate pH4.5 (adjusted with 85% phosphoric acid):methanol:acetonitrile (94:4.5:1.5, v/v) at a flow rate of 1.0mLmin-1. The detection was done at 254nm. The lower limit of quantification in rabbit AH was 100.0ngmL-1. The method was validated according to EMA guidelines. The method was confirmed to be accurate, precise and linear over a range of 100.0-1000.0ngmL-1 for BM and BZ. The method developed herein is simple, safe, eco-friendly, rapid and accurately applied for the quantification of BM and BZ, along with the successful separation of NDBZ, which is considered as a potential irritant degradation product of BZ.

Emerging Alternaria toxins present in naturally contaminated dried tomatoes and their reduction using cold atmospheric plasma

This study investigated the efficacy of cold atmospheric plasma (CAP) treatment in degrading the emerging Alternaria toxins as pure molecules and as natural contaminants in dried tomatoes. The analyses of 25 batches of dried tomatoes showed that more than 40% of samples were contaminated with tenuazonic acid (TeA), one with Alternariol (AOH), while Tentoxin (TEN), Alternariol monomethyl ether (AME) and Altenuene (ALT) were not detected. CAP under ozone (O3) and NOx regimes were used to reduce the mycotoxin contamination, the results shown that O3 regime was more effective against all mycotoxins tested, while NOx regime showed different efficacy depending on the specific mycotoxin. The Weibull model proved to be appropriate for the degradation kinetics of all Alternaria toxins, regardless of the kinetic order they possess. Under the O3 regime, the resistance of the mycotoxin was AME > AOH > TEN > TeA > ALT. Our studies have shown for the first time that CAP reduces Alternaria toxins in naturally contaminated dried tomatoes. In particular, the rate of degradation under O3 regime increased significantly with the longest exposure time, reaching 52.80 ± 1.21 % of mycotoxin degradation. Our results expand our knowledge of CAP treatment as a potential means of reducing mycotoxin contamination in food. Further studies will be carried out to investigate the potential mycotoxin degradation products and to ensure food safety.

Identification and structural characterization of potential degradation products of baricitinib using liquid chromatography combined with quadrupole time-of-flight mass spectrometry

AbstractBaricitinib (BRT) is a drug substance with potent anti-inflammatory activity indicated in rheumatoid arthritis, atopic dermatitis, severe alopecia areata and recently for the treatment of Covid-19. Process impurities of the drug during its formulation are quite known, however studies regarding its degradation products (DPs) under stress conditions are limited. In this study, the drug was subjected to forced degradation under various degradation conditions, including acidic hydrolysis, alkaline hydrolysis, oxidative and thermal, to determine its inherent stability. To this purpose, a novel HPLC method was developed for the determination of degradation impurities of BRT. Alkaline hydrolysis test showed a selectivity towards breaking C–C bonds. This resulted to five DPs formed by chain scission reactions occurred at the pyrrolo-pyrimidine group between C6–C10 and C8–C9. Also, the ethylsulfonyl-azetidin-ylidene group was subjected to C–C bond cleavage at C12–C15 and C16–C18. Degradation products were further characterized with the use of liquid chromatography quadrupole time of flight tandem mass spectrometry (LC-Q-TOF-MS/MS).

Exploratory DSC investigation on the solvolytic depolymerization of PET in varied solvent systems and in the presence of model additives and contaminants

Solvolytic depolymerization of polyethylene terephthalate (PET) is a thermo-chemical recycling route that valorizes plastic waste by recovering monomers and chemicals that can be reused for the synthesis of new polymers. This study focuses on neutral hydrolysis due to the potential environmental and economic benefits of water as depolymerization agent compared to alternative organic solvents. High-pressure crucibles were used as batch reactors in differential scanning calorimetry (DSC) to perform real-time monitoring of the thermodynamic phenomena taking place during solvolytic depolymerization of PET in varied solvent systems. PET melting point depression was found to be the main identified phenomena, with PET melting point exhibiting a drop of almost 30 °C in water and 50 °C in monoalcohol solvents like methanol and ethanol. Moreover, PET only underwent significant depolymerization prior to melting in NaOH containing systems. Gas Chromatography and Mass Spectrometry were used to study the fate of model additives and contaminants under solvolytic conditions. The uncertainty concerning these foreign substances poses a challenge for the development of PET solvolytic technologies, and the methods here provided proved to be a fast-screening technique to quantify the conversion and identify potential degradation products of model additives like 2-(2-hydroxy-5-methylphenyl) benzotriazole UV-stabilizer, 1-(methylamino) anthraquinone dye, and model contaminant (R)-(+)-limonene under hydrothermal conditions.

Comparing the Aging Processes of PLA and PE: The Impact of UV Irradiation and Water

The aging processes of microplastics (MPs) are prevalent in natural environments. Understanding the aging mechanisms of MPs is crucial for assessing their environmental behavior and potential risks. In this study, we selected polylactic acid (PLA) and polyethylene (PE) as representatives of biodegradable and conventional plastics, respectively, to examine changes in their physicochemical properties induced by water and UV light exposure. Laboratory aging resulted in significant fragmentation, characterized by cracks and pores on the surfaces, for both types of MPs, with PLA MPs exhibiting more severe changes, particularly under combined UV and water exposure. Notably, PLA MPs tended to become progressively smaller after aging, whereas PE MPs did not show significant size changes. Chemical analyses of aged MPs using micro-Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) revealed a substantial increase in the carbonyl index (CI) and oxygen content for PE, suggesting surface oxidation during photo-oxidation. Conversely, PLA MPs displayed a CI decrease, along with an oxygen content increase, indicating the breakdown of ester linkages in PLA and the formation of other oxidation products. Furthermore, we developed and optimized pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) methods to identify potential chemical degradation products of PE and PLA, considering their differing thermal stabilities. We observed a distinct trend regarding the peaks in the chromatogram of aged MPs and identified the typical oxidation and crosslinking products for PLA. Additionally, after the aging process, both PE and PLA exhibited a significant increase in organic carbon content, with the eluate containing submicron/nano-sized particles. This study provides a scientific foundation for a deeper understanding of the environmental aging mechanisms of various MPs, particularly in regards to the effects of UV irradiation and water exposure.

New benzimidazole based Schiff bases as potent anti-alzheimer agents: Synthesis, bio-evaluation and molecular docking study

In search of potent anti-Alzheimer agent benzimidazole based Schiff base derivatives (1–18) were synthesized and evaluated as dual inhibitor for acetylcholinesterase and butyrylcholinesterase enzymes. All analogs among the series except analog 1 and 16 showed a variable degree of inhibitory activity with IC50 value ranging between 0.10 ± 0.01 to 12.40 ± 0.30 µM for acetylcholinesterase and 0.20 ± 0.01 to 11.10 ± 0.30 µM for butyrylcholinesterase. The most potent analog found among the series was analog 8 having IC50 value 0.10 ± 0.01 and 0.20 ± 0.01 µM for both acetylcholinesterase and butyrylcholinesterase inhibition respectively. The structures of all synthesized analogs were confirmed through NMR and HR-EIMS. Structure activity relationship (SAR) has been established for all newly synthesized derivatives. To understand the binding interaction of most active derivatives with enzyme active site, molecular docking study were performed. The toxicity and mutagenicity of compound 8 was predicted using in silico software, namely Derek Nexus® (version 6.3). Various toxicity endpoints, including chromosomal damage, skin sensitization, hepatotoxicity were predicted. The degradation profile of compound 8 was predicted in silico by Zeneth software (version 9.0.1) resulting in a probability of the formation of seven potential degradation products.

Degradation kinetics of β-nicotinamide mononucleotide based on reliable HPLC quantitative method

To explore the stability characteristics of β-nicotinamide mononucleotide(NMN) and provide data support for NMN production, preparation, and related product development, this study established a simple HPLC content determination method for NMN in simple substrate and investigated the degradation behavior, degradation products, and degradation kinetics of NMN under various chemical, physical, and biological conditions. The HPLC method employed a Welch Xtimate AQ-C_(18) column(4.6 mm×250 mm, 5 μm), a detection wavelength of 266 nm, a column temperature of 30 ℃, a flow rate of 1.0 mL·min~(-1), an injection volume of 5 μL, and a mobile phase consisting of methanol(A) and a 10 mmol·L~(-1) ammonium formate aqueous solution(B) with a gradient elution(0-6.7 min, 0-4% A; 6.7-13 min, 4%-18% A; 13-14.2 min, 18% A; 14.2-15 min, 18%-0 A; 15-22 min, 0 A). This method provided good separation between NMN and potential impurities and degradation products, and had a wide linear range, short analysis time, good durability, high accuracy, an average sample recovery rate of 98.71%, and an RSD of 1.2%. The instrument precision had an RSD of 0.26%, and the linearity within the examined range was excellent(R~2≥0.999 9). This method can be applied for NMN content determination in simple substrate. The degradation process of NMN in aqueous solution followed apparent first-order kinetics, with the degradation rate primarily influenced by high temperature and pH. NMN was more stable in low-temperature, neutral, or weakly acidic/alkaline environments. Strong acids or strong alkalis could accelerate its degradation, and its degradation rate was less affected by pepsin and trypsin. In an aqueous solution at room temperature, it followed the kinetic equation lg C_t=0.005 7t + 4.817 2, with t_(0.9) and t_(1/2) values of 95.58, 860.26 h, respectively. The results suggest that pH and temperature are the main factors affecting the stability of NMN in aqueous solution, and low temperature, moisture protection, and a weakly acidic environment are more conducive to the storage and application of NMN and its products.

Pressurized metered-dose inhalers using next-generation propellant HFO-1234ze(E) deposit negligible amounts of trifluoracetic acid in the environment

Pressurized metered-dose inhalers (pMDIs) deliver life-saving medications to patients with respiratory conditions and are the most used inhaler delivery device globally. pMDIs utilize a hydrofluoroalkane (HFA), also known as an F-gas, as a propellant to facilitate the delivery of medication into the lungs. Although HFAs have minimal impact on ozone depletion, their global warming potential (GWP) is more than 1,000 times higher than CO2, bringing them in scope of the F-Gas Regulation in the European Union (EU). The pharmaceutical industry is developing solutions, including a near-zero GWP “next-generation propellant,” HFO-1234ze(E). At the same time, the EU is also evaluating a restriction on per-and polyfluoroalkyl substances (PFAS) under the Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) regulation. Trifluoroacetic acid (TFA) is a persistent PFAS and a potential degradation product of HFO-1234ze(E). We quantified yield of TFA from HFO-1234ze(E) using a computational model under Europe-relevant atmospheric conditions. The modeling suggests that most HFO-1234ze(E) degrades into formyl fluoride within 20 days (≥85%) even at the highest examined altitude. These results suggest that TFA yield from HFO-1234ze(E) varies between 0%–4% under different atmospheric conditions. In 2022, France represented the highest numbers of pMDI units sold within the EU, assuming these pMDIs had HFO-1234ze(E) as propellant, we estimate an annual rainwater TFA deposition of ∼0.025 μg/L. These results demonstrate negligible formation of TFA as a degradation product of HFO-1234ze(E), further supporting its suitability as a non-persistent, non-bioaccumulative, and non-toxic future propellant for pMDI devices to safeguard access for patients to these essential medicines.

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.

Green sustainable assessment of stability indicating first derivative synchronous fluorimetry for determination of anti-diabetic drug with its toxic impurity

Canagliflozin is prescribed with proper diet and exercise for the treatment of type 2 diabetes mellites. In this work, simple and sensitive synchronous fluorescence spectroscopic method coupled with the first derivative was proposed for the quantitative determination of canagliflozin in the presence of its oxidative degradation product. Canagliflozin and its oxidative degradation product have native fluorescence at 353 nm and 364 nm after excitation at 294 nm and 289 nm, respectively. The application of synchronous fluorescence mode gave a sharp peak but failed to resolve canagliflozin and its potential toxic degradation product. First-order derivatization of synchronous spectra resolved the overlap and allowed the determination of canagliflozin in the presence of its oxidative degradation product at 324 nm using Δλ = 20 nm. The method showed linearity with excellent correlation in the concentration range of 1–20 μg/mL for canagliflozin. The method was successfully applied for the determination of canagliflozin in pharmaceutical formulation and laboratory-prepared mixtures with mean percent recovery of 99.95 ± 1.14 and 99.81 ± 1.06, respectively. The greenness of the proposed method was assessed and approved by different tools such as analytical eco-scale, green analytical procedure index GAPI and AGREE.

Hesperidin: Enrichment, forced degradation, and structural elucidation of potential degradation products using spectral techniques.

Hesperidin (HES) is a well-known citrus bioflavonoid phyto-nutraceutical agent with polypharmacological properties. After 2019, HES was widely used for prophylaxis and COVID-19 treatment. Moreover, it is commonly prescribed for treating varicose veins and other diseases in routine clinical practice. Pharmaceutical impurities and degradation products (DP) impact the drug's quality and safety and thus its effectiveness. Therefore, forced degradation studies help study drug stability, degradation mechanisms, and their DPs. This study was performed because stress stability studies using detailed structural characterization of hesperidin are currently unavailable in the literature. In the HES enrichment method crude HES was converted to its pure form (98% purity) using column chromatography and then subjected to forced degradation under acid, base, and neutral hydrolyses followed by oxidative, reductive, photolytic, and thermal stress testing (International Conference on Harmonization guidelines). The stability-indicating analytical method (SIAM) was developed to determine DPs using reversed-phase high-performance liquid chromatography (C18 column with methanol and 0.1% v/v acetic acid in deionized water [70:30, v/v] at 284 nm). Further, structural characterization of DPs was performed using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) and nuclear magnetic resonance (NMR) spectroscopy. In addition, in silico toxicity predictions were performed using pKCSM and DataWarior freeware. HES was found to be susceptible to acidic and basic hydrolytic conditions and yielded three DPs in each, which were detected using designed SIAM. Of six DPs, three were pseudo-DPs (short lived), and the remaining were characterized using LC-MS/MS and NMR spectroscopy. The tentative mechanism of the formation of proposed DPs was explained. The proposed DPs were found inactive from in silico toxicity predictions. Hesperidin was labile under acidic and basic stress conditions. The potential DPs were characterized using LC-ESI-MS/MS and NMR spectral techniques. The proposed mechanism of formation was hypothesized. In addition, to identify and characterize the DPs, a SIAM, which has broad biomedical applications, was successfully developed.

Effective degradation of tetracycline by Pd/AG/ITO electrode: Electrode preparation, characterization, kinetics, degradation mechanism and toxicity assessment

The presence of antibiotics such as Tetracycline (TC) in the water environment poses new challenges to traditional water treatment technologies. Simple and clean electrocatalytic technology has been widely used in the degradation of antibiotic-based wastewater. In this study, agarose (AG) was loaded onto ITO using an impregnation method, and Pd was deposited onto the AG/ITO electrode by electrodeposition, the Pd/AG/ITO composite electrode was prepared. The electrode was then observed and analyzed using SEM, XRD, FT-IR, and XPS. The optimal conditions for the electrocatalytic reaction were explored as follows: PdCl2 concentration of 0.20 mmol/L, PdCl2 deposition current of 3 mA, deposition time of 10 min, and degradation current of 8 mA. Under these optimal working conditions, the Pd/AG/ITO composite electrode achieved a degradation efficiency of 85.21% within 120 min. Through five replications, the degradation efficiency of the electrodes decreased by less than 3.50%, which indicated its good reusability and stability. Based on the generation of active substances during degradation and the analysis of LC-MS, potential degradation products, and degradation pathways were deduced, and it was proposed that the degradation of TC was completed by a synchronous redox reaction co-led by·OH and H*. Toxicity analysis of TC and its degradation products was performed using ECOSAR software. This study will promise to provide an effective method of degrading TC wastewater.

A new concept for the ecotoxicological assessment of plastics under consideration of aging processes

AbstractMicroplastics are widely distributed in aquatic and terrestrial environments, but up to now less is known about (eco)toxicological impacts under realistic conditions. Research so far has focused mainly on impacts on organisms by fresh, single‐origin plastic fragments or beads. However, plastics found in the environment are complex in composition, this means different polymer types and sources, with and without additives and in all stages of age, and therefore, in a more or less advanced stage of degradation. For oxidized degradation products that might be released from plastic materials during aging, there is a lack of information on potentially adverse effects on aquatic biota. The latter is of particular interest as oxidized degradation products might become more water soluble due to higher polarity and are more bioavailable, therefore. The present study focused on plastic leachates of polystyrene (PS) and polylactic acid (PLA), which were derived from alternating stress by hydrolysis and ultraviolet (UV) radiation—representing a realistic scenario in the environment. Test specimens of PS, PLA, or a PLA/PS layer (each 50%) were alternately exposed to UV radiation for 5 days followed by hydrolysis for 2 days, for several weeks alternating. Ecotoxicological effects of the storage water (artificial freshwater) of the test specimens and additionally, in a second experimental setup, the effects of five potential polymer degradation products were detected by 72 h algae growth inhibition tests with Desmodesmus subspicatus. Results clearly indicate inhibitory effects on algae growth by contaminants in the storage water of stressed plastics with increasing growth inhibition of proceeding hydrolysis and UV stress times. Different polymers caused variable inhibitions of algae growth with stronger inhibitions by PS and less effects by PLA and the mixed layer of both. Moreover, not microplastic particles but the resulting dissolved degradation products after aging caused the ecotoxicological effects—with strong effects by the oxidized degradation products. The existing data highlight the relevance of plastic aging as a framework for microplastic ecotoxicity evaluation and allow a proof of concept.

A Review on Force Degradation Studies for Drug Substances

The objective of the review article is to give detailed description and guidance of the forced degradation studies as per regulatory guidelines. Forced degradation or alternatively referred as stress testing and it demonstrates specificity when developing stability indicating methods, especially when little is known about potential degradation products. Forced degradation study provides information about the degradation pathways and degradation products of the drug substance that could form during storage, transportation. Force degradation study also helps in the elucidation of the structure of the degradation products. Forced degradation study provide the chemical behaviour and chemical nature of the molecule which ultimately helps in the development of formulation during manufacturing and packaging specification, thus this review article provides knowledge of the current trends in performance of forced degradation study and establishing the analytical methods that helpful for development of stability indicating method.

Comparative Study on the Microstructure and Biodegradation Behavior of Commercialized Pure Mg and Mg-1.0Ca-0.5Sr Alloy in 27 mM HCO3−-SBF: The Influence of the pH Regulation Treatments

The biodegradation behavior of newly developed orthopedic implant materials provides essential insight into the potential degradation products and their ability to match the rate of bone healing prior to complete degradation. Ironically, biodegradation performance is not only influenced by alloy design or advanced surface treatment on the alloy, but also it is dominantly controlled by the specific inorganic species and their concentration in the corrosion media as well as their pH level. In this study, the biodegradation behavior of commercially pure magnesium (CP Mg) and a Mg-1.0Ca-0.5Sr alloy was evaluated in 27 mM HCO3−- Simulated Body Fluid (r-SBF) due to its identical ionic species and concentrations with human blood plasma via immersion test, including (i) hydrogen evolution test (H2), (ii) pH trend, and (iii) weight-loss measurement. To simulate the pH regulation by the physiological homeostatic response, the pseudo-physiological solution was treated with two treatments: through a (i) a 24 h corrosion media renewal routine and through the use of (ii) a TRIS-HCL buffer reagent. The Mg-1.0Ca-0.5Sr alloy is shown to have superior corrosion resistance due to grain refinement and unique secondary phases, whereas the daily renewal routine imparts a better emulation of in vivo corrosion control.

Isolation and structural characterization of two novel oxidative degradation products of losartan potassium active pharmaceutical ingredient using advanced analytical techniques.

Losartan potassium (losartan) is the most frequently utilized antihypertensive medication in the world. However, partial oxidation of losartan produces toxic by-products that could be harmful to living organisms. Therefore, it is necessary to degrade the losartan and identify the potential toxic oxidative degradation products to minimize their formation during manufacturing, formulation, storage, and packing conditions. Oxidative degradation experiments of losartan were performed according to ICH guidelines. The degradation products were detected using ultra-high-performance liquid chromatography-mass spectrometry analysis, isolated by using preparative HPLC, and identified by using high-resolution mass spectrometry and nuclear magnetic resonance spectroscopic techniques. The degradation products (DP-1, DP-2, and DP-3) were identified as (((2'-(2H-tetrazol-5-yl)-[1,1'-biphenyl]-4-yl)methyl)amino)-2-oxoethylpentanoate, 5-(4'-((2 butyl-4-chloro-5-(hydroxymethyl)-1H-imidazol-1-yl)methyl)-[1,1'-biphenyl]-2-yl)-1H tetrazol-1-ol, and 5-(4'-((2-butyl-4-chloro-5-(hydroxymethyl)-1H-imidazol-1 yl)methyl)-[1,1'-biphenyl]-2-yl)-2H-tetrazol-2-ol, respectively. Forced degradation of losartan potassium API under oxidative condition indicates the formation of two major novel oxidative degradation products (DP-2 and DP-3) and one minor known degradation product (DP-1).Preparative HPLC used for the isolation of the resultant DPs and their structures were successfully established using UHPLC-MS, 1H NMR, 13C NMR, HSQC, HMBC, and HRMS spectroscopic techniques.

Study of Degradation Kinetics and Structural Analysis of Related Substances of Ceftobiprole by HPLC with UV and MS/MS Detection

Ceftobiprole is a novel β-lactam antibiotic, active against methicillin-resistant Staphylococcus aureus, vancomycin-resistant S. aureus and penicillin-resistant Streptococcus pneumoniae. To artificially generate potential degradation products (DPs) of ceftobiprole that may be formed under relevant storage conditions, acidic, alkaline, oxidative, photolytic and thermolytic stress tests were performed in both solution and solid state. A novel selective HPLC method was developed for the separation of ceftobiprole from its DPs and synthesis by-products (SBPs) using Kinetex Biphenyl column, ammonium acetate buffer pH 5.8 and acetonitrile. The kinetic studies demonstrated the low stability of ceftobiprole in alkaline solution, in the presence of an oxidising agent and under irradiation with near UV. In the solid state, ceftobiprole underwent oxidation when the powder was irradiated with visible light and UV. Based on mass spectroscopic analysis, 13 new structural formulas of SBPs and DPs were proposed, along with molecular formulas for three other DPs obtained in solution and four oxidative DPs characteristic of solid-state degradation.

Biodegradation of MC-LR and its key bioactive moiety Adda by Sphingopyxis sp. YF1: Comprehensive elucidation of the mechanisms and pathways

Microcystins (MCs) are harmful to the ecology and public health. Some bacteria can degrade MCs into Adda, but few can destroy Adda. Adda is the key bioactive moiety of MCs and mainly contributes to hepatotoxicity. We had previously isolated an indigenous novel bacterial strain named Sphingopyxis sp. YF1 that can efficiently degrade MCs and its key bioactive moiety Adda, but the mechanisms remained unknown. Here, the biodegradation mechanisms and pathways of Adda were systematically investigated using multi-omics analysis, mass spectrometry and heterologous expression. The transcriptomic and metabolomic profiles of strain YF1 during Adda degradation were revealed for the first time. Multi-omics analyses suggested that the fatty acid degradation pathway was enriched. Specifically, the expression of genes encoding aminotransferase, beta oxidation (β-oxidation) enzymes and phenylacetic acid (PAA) degradation enzymes were significantly up-regulated during Adda degradation. These enzymes were further proven to play important roles in the biodegradation of Adda. Simultaneously, some novel potential degradation products of Adda were identified successfully, including 7‑methoxy-4,6-dimethyl-8-phenyloca-2,4-dienoic acid (C17H22O3), 2-methyl-3‑methoxy-4-phenylbutyric acid (C12H16O3) and phenylacetic acid (PAA, C8H8O2). In summary, the Adda was converted into PAA through aminotransferase and β-oxidation enzymes, then the PAA was further degraded by PAA degradation enzymes, and finally to CO2 via the tricarboxylic acid cycle. This study comprehensively elucidated the novel MC-LR biodegradation mechanisms, especially the new enzymatic pathway of Adda degradation. These findings provide a new perspective on the applications of microbes in the MCs polluted environment.

Characterization of potential degradation products of brexpiprazole by liquid chromatography/quadrupole-time-of-flight mass spectrometry and nuclear magnetic resonance, and prediction of their physicochemical properties by ADMET Predictor™.

Brexpiprazole (BRZ) was subjected to hydrolytic (acid, base and neutral), oxidative, photolytic and thermal stress degradation in solutions prepared in a mixture of acetonitrile-water (70:30 v/v). The oxidative study was additionally done in methanol-buffer mixture at pH3, 7 and 11. Also, compatibility of the drug with selectedexcipients was investigated in the solid state. Additionally, physicochemical and ADMET properties of BRZ and its degradation products (DPs) were predicted using ADMET Predictor™ software. It provides the conditions for quality control of BRZ and its derivatives during manufacturing, processing and storage conditions. The formed DPs were separated from the drug and among themselves on a C-18 column utilizing mobile phase composed of methanol and ammonium formate buffer (10mM, pH4.0), which was run in a gradient mode. Characterization of DPs was carried out by first establishing the mass fragmentation pathway of the drug based on its liquid chromatography/quadrupole-time-of-flight mass spectrometry (LC/Q-TOF-MS) data, followed by LC/Q-TOF-MS studies of DPs. Three DPs were isolated and, along with the drug, they were subjected to 1D (1 H, 13 C and DEPT-135) and 2D (COSY and HSQC) NMR studies for confirmation of their structures. BRZ was observed to be susceptible to hydrolytic (neutral, acid and alkali), photolytic and oxidative degradation conditions; it was stable on thermal exposure. A total of 12 DPs (BRZ-1 to BRZ-12) were formed in solution state. Mechanisms of BRZ degradation were postulated. The extent of degradation of BRZ in different stress conditions highlights that stability of BRZ in drug formulations can be improved (i) by using excipients that can impart a low-pH microenvironment, (ii) by addition of antioxidants and (iii) through protection from light.

In vitro degradation of ziprasidone in human whole blood.

A systematic study was performed into the degradation of ziprasidone in simulated postmortem blood. Fifteen potential degradation products not previously reported in the literature were observed. Four resulted from degradation in human blood, whereas the remaining products resulted from reaction with solvents: four from alkaline degradation, four from reaction with acetaldehyde, and three from reaction with acetone. To identify possible degradation products, a liquid chromatograph-diode array detector (LC-DAD) and liquid chromatograph quadrupole-time-of-flight mass spectrometer (LC-QTOF-MS) operating in auto-MS/MS mode were used. It was indicated from red-shifted UV-Vis spectra, accurate mass data, mass fragmentation data, and a deuteration experiment that the site of ziprasidone degradation, in the in vitro blood experiments, was the methylene carbon of the oxindole moiety. The major in vitro blood degradation products were proposed to be E/Z isomers of 3-ethylidene-ziprasidone. Further, another in vitro degradation product in microbially inoculated blood specimens was proposed to be 3-ethyl-ziprasidone. 3-Ethylidene-ziprasidone was hypothesized to form from the reaction of ziprasidone with acetaldehyde derived from the ethanol used to spike ziprasidone into the in vitro blood experiments. Data from two postmortem investigations were available for retrospective reanalysis. Attempts were made to detect degradation products of ziprasidone, but none were found.