Major Degradation Products Research Articles

A stability-indicating assay HPLC method of ketoprofen

The present official method for the assay and analysis of the ketoprofen related substances as described in the British Pharmacopeia is redox titration and thin layer chromatography. The assay method of ketoprofen preparation in the United States Pharmacopeia is an UV/VIS method. The National Laboratories of Foods and Drugs, ROC, require a rapid, sensitive and precise method for the analysis of large numbers of samples including those for ketoprofen. Since the existing official methods for ketoprofen are not all specific for ketoprofen, a specific HPLC method is then desirable. This report presents such an approach. The HPLC system consisted of a Zorbax ODS C18 (4.6 x 150 mm) and a mobile phase of aqueous KH2PO4 with glacial acetic acid in CH3CN (55/45. v/v) at pH 2.5. A flow rate of 1.2 ml/min, UV detection at 265 nm and attenuation of 0.02 aufs were performed. The system suitability was established, and the statistical validation of the performance was carried out for linearity, accuracy and precision. Different chromatograms were observed for the acid, base and photo-degraded samples. The results suggest that different degradation reaction followed different mechanism. The major different degradation products resulting from acid, base and photo-degradation of ketoprofen were separated by this HPLC method.

Intrinsic stability study of L-α-glycerylphosphorylcholine with HPLC method development and validation

L-α-Glycerylphosphorylcholine (L-α-GPC) is effective to control the symptoms of cognitive decline for the patients of Alzheimer’s disease. In this study, an HPLC method coupled with a refractive index detector was developed to evaluate the intrinsic stability of L-α-GPC. The separation of L-α-GPC and its major potential degradation products was achieved on a normal-phase silica gel column (4.6 mm × 250 mm) with the mobile phase consisting of methanol–20 mM ammonium formate aqueous solution (pH 3.2) (65:35, v/v) in isocratic mode. The HPLC method was validated satisfactorily with respect to precision, accuracy and robustness. It is found that L-α-GPC is stable under the photolytic, thermal, oxidative and acidic conditions, while relatively sensitive to alkaline condition due to the specific breakage of phosphate ester bond in the moiety of L-α-GPC. A preliminary kinetics study for the alkaline degradation was conducted with the corresponding kinetics parameters obtained. It can be concluded that the developed HPLC method is capable of distinguishing the stability difference between the two phosphate ester bonds characterized on the L-α-GPC chemical structure.

Identification and characterization of forced degradation products of vortioxetine by LC/MS/MS and NMR

Vortioxetine (VTX) is a novel multimodal antidepressant drug that affects the serotoninergic and noradrenergic systems. In this work, the forced degradation of VTX was studied according to (ICH) Q1A (R2) guidelines. The study revealed that VTX was stable under thermal stress conditions and hydrolytic stress conditions i.e., acidic, basic and neutral conditions. In contrast, six degradation products (DPs) were formed under photolytic and oxidative stress conditions. The DPs were identified and characterized by high-resolution LC/MS and LC/MS/MS. The structures of major DPs were further confirmed by the synthesis and characterization by 1H and 13C NMR data. A possible mechanism for the formation of the VTX DPs via photolytic/oxidative stress degradation pathway was proposed.

BiOCl0.875Br0.125/polydopamine functionalized PVDF membrane for highly efficient visible-light-driven photocatalytic degradation of roxarsone and simultaneous arsenic immobilization

A bifunctional membrane modified by BiOCl0.875Br0.125 and polydopamine (PDA) was developed in the current study and employed for the photocatalytic degradation of roxarsone (ROX) under visible-light and simultaneous immobilization of the released inorganic arsenic by sorption. Characterization techniques, such as FESEM, XRD, FTIR-ATR, DRS and XPS were used to characterize as-prepared membranes so as to analyze their structural and functional attributes. Dynamic cyclic experiments indicated that a satisfactory degradation efficiency of ROX (∼100%) could be achieved by the photocatalytic process within 5 h. Simultaneously, the released inorganic arsenic could be completely converted to As(V) and eventually immobilized onto the surface of membrane. The critical reactive oxidation species (ROS) including O2−, h+ and OH contributed to the photodegradation of ROX, and the PDA coating played multiple roles as an adhesive interface, an electron transfer layer, and an active adsorptive layer. Additionally, based on the HPLC-AFS and GC–MS analysis, the major degradation products were detected and the mechanism of ROX degradation and simultaneous arsenic immobilization by BiOCl0.875Br0.125/PDA functionalized PVDF membranes (BPMs) was given, and the reaction pathway of ROX during the photocatalytic/filtration process was also taken into consideration. Combined with the exceptional photocatalytic property and high adsorption capacity of arsenic, the fabricated BPMs may open new opportunities for the control of ROX in water treatment.

A novel sulfite coupling electro-fenton reactions with ferrous sulfide cathode for anthracene degradation

In the present study, pyrite modified carbon felt (FeS2/CF) was used as cathode in electrochemical advanced oxidation for the first time. The FeS2/CF cathode can provide Fe(II) and oxysulfide continuously through this sulfite coupling heterogeneous electro-Fenton (HEF) process without leaching of iron, which further induced the formation of SO4∙− and OH. The cumulative concentration of OH was 26.83 μM after 20 min at the current density of 10 mA cm−2, which was about twice higher than that in the electrochemical system with CF only. The estimated steady-state concentrations of SO4∙− and OH in this HEF system can be as high as 7.37 × 10−4 μM and 2.44 × 10−4 μM, respectively. This electrochemical system with FeS2/CF cathode shows remarkable efficiency (>80%) for anthracene (ANT) degradation in a wide pH of 3–9, and can be used for at least six times. The major degradation products of ANT were identified as anthraquinone and other four hydroxylated products. The study provides a novel aspect of FeS2 in HEF processes, and is expected to be an efficient technology in water treatment processes.

Isomeric stability of indaziflam and major degradation products in the environment

Understanding the isomeric behavior of active ingredients in the soil and water environment is the first and a major part of deriving an exposure assessment. Whilst a variety of approaches have been taken previously, with the new regulatory framework for the risk assessment of isomeric plant protection compounds recently published by EFSA, (European Food Safety Authority) there will in future be a more consistent approach which has been taken here. For indaziflam (IAF), the alkylazine, cross spectrum residual herbicide which has a cellulose biosynthesis inhibition mode of action, there was no published data on the isomeric degradation behavior in soil and water. The results of measuring the isomeric stability of [14C]-radiolabeled 437-IAF, the major stereoisomer of indaziflam (AE 1170437, [1R,2S,6R] configuration) during its degradation in an aerobic soil metabolism study with four EU soils, an aerobic aquatic metabolism study with two natural water/sediment test systems, as well as an aqueous photolysis study are reported. To sum up, it was shown that in the different environmental conditions under abiotic as well as biotic degradation processes, indaziflam was not subject to isomeric interconversion to diastereoisomers 435-IAF (RRR), 438-IAF (RSS), or 439-IAF (SSR). Thus, all three chiral centers of indaziflam can be considered isomerically stable. In addition, no isomeric interconversion was observed at the 1-fluoroethyl position for the major degradation products IAF-indanone and IAF-carboxylic acid to the RSS-configuration as well as IAF-diaminotriazine from the R- to the S-configuration.

Photolytic and photocatalytic degradation of doxazosin in aqueous solution

Doxazosin (DOX), a selective alpha blocker, is widely used in medical therapy as an effective antihypertensive agent. It is a frequently prescribed drug and for this reason, environmental and ecotoxicological research is of great importance in terms of exposure and risk for both aquatic species and humans. In this study we focused on photolytic and TiO2 photocatalytic degradation processes of doxazosin under different simulated conditions, with the emphasis on identification of degradation products. Photolytic (without TiO2) experiments were performed in the presence and absence of oxygen, while photocatalytic degradation of doxazosin aqueous solution has been carried out under constant oxygen flow. DOX degradation was more efficient in the TiO2/UVA photocatalytic experiment than during photolytic processes (UVA and UVC, UVC-N2).LC-HRMS analyses with electrospray ionization allowed observing the formation of several major degradation products depending on the reaction conditions (presence or absence of oxygen, photocatalysis). The transformation products were identified based on exact mass measurements, isotopic distribution, and fragmentation pattern. Among them, dominated C17H21N5O3 and C17H23N5O4 (cleavage of the dioxane cycle), and C23H25N5O7 (hydroxylation). The detailed degradation pathway has been proposed.Toxicity testing with V. fischeri luminescent bacteria revealed higher toxicity of samples in photolytic rather than photocatalytic experiments which might be attributed to the formation of different products.

Capillary electrophoresis-mass spectrometry for the direct analysis of glyphosate: method development and application to beer beverages and environmental studies

In this study, we developed and validated a CE-TOF-MS method for the quantification of glyphosate (N-(phosphonomethyl)glycine) and its major degradation product aminomethylphosphonic acid (AMPA) in different samples including beer, media from toxicological analysis with Daphnia magna, and sorption experiments. Using a background electrolyte (BGE) of very low pH, where glyphosate is still negatively charged but many matrix components become neutral or protonated, a very high separation selectivity was reached. The presence of inorganic salts in the sample was advantageous with regard to preconcentration via transient isotachophoresis. The advantages of our new method are the following: no derivatization is needed, high separation selectivity and thus matrix tolerance, speed of analysis, limits of detection suitable for many applications in food and environmental science, negligible disturbance by metal chelation. LODs for glyphosate were < 5 μg/L for both aqueous and beer samples, the linear range in aqueous samples was 5–3000 μg/L, for beer samples 10–3000 μg/L. For AMPA, LODs were 3.3 and 30.6 μg/L, and the linear range 10–3000 μg/L and 50–3000 μg/L, for aqueous and beer samples, respectively. Recoveries in beer samples for glyphosate were 94.3–110.7% and for AMPA 80.2–100.4%. We analyzed 12 German and 2 Danish beer samples. Quantification of glyphosate and AMPA was possible using isotopically labeled standards without enrichment, purification, or dilution, only degassing and filtration were required for sample preparation. Finally, we demonstrate the applicability of the method for other strong acids, relevant in food and environmental sciences such as N-acetyl glyphosate, N-acetyl AMPA (present in some glyphosate resistant crop), trifluoroacetic acid, 2-methyl-4-chlorophenoxyacetic acid, glufosinate and its degradation product 3-(methylphosphinico)propionic acid, oxamic acid, and others.

HPLC-UV Method for Standardization of Neorautanenia mitis, an African Plant Used in an Anti-Scabies Ointment

An HPLC-UV method for standardization of the methanol-soluble extracts from tubers of Neorautanenia mitis (A.Rich.) Verdc., Fabaceae, harvested during different periods and from different sites, is described. The chemical fingerprint was established with six identified markers using LC-ESI (+)-MS/MS, including rotenone; the total error was used as validation criterion, the accuracy and risk profiles demonstrated the reliability of the method. The study verified that the major degradation product of rotenone in methanol is dehydrorotenone. The detection range of rotenone was between 40 and 400 μg/ml. The collected samples contained 868–5732 μg/g of rotenone. The concentrations of rotenone in the wild samples from the Ngoma site (5167 ± 565 μg/g) were higher than those registered in the samples from the other sites. No significant differences were observed among the remaining sampling sites, and most of the rotenone was located in the inner part of the tubers (2165 ± 1051 μg/g) when compared with that in their peels (961 ± 320 μg/g).

Comprehensive and quantitative stability study of ascorbic acid using capillary zone electrophoresis with ultraviolet detection and high-resolution tandem mass spectrometry.

Ascorbic acid is a powerful antioxidant compound involved in many biological functions, and a chronic deficiency is at the origin of scurvy disease. A simple, rapid, and cost-effective capillary electrophoresis method was developed for the separation and simultaneous quantification of ascorbic acid and the major degradation products: dehydroascorbic acid, furfural, and furoic acid. Systematic optimization of the conditions was performed that enabled baseline separation of the compounds in less than 10min. In addition to simultaneous quantification of ascorbic acid alongside to the degradation products, stability studies demonstrated the possibility using capillary electrophoresis to separate and identify the major degradation products. Thus, high-resolution tandem mass spectrometry experiments were conducted in order to identify an unknown degradation product separated by capillary electrophoresis and significantly present in degraded samples. Comparison of mass spectrometry data and capillary electrophoresis electropherograms allowed to identify unambiguously trihydroxy-keto-valeraldehyde. Finally, capillary electrophoresis was successfully applied to evaluate the composition of different pharmaceutical preparation of ascorbic acid. Results showed the excellent performance of the capillary electrophoresis method due to the separation of excipients from the compounds of interest, which demonstrated the relevance of using an electrophoretic separation in order to perform comprehensive stability studies of ascorbic acid.

Rapid degradation of dichloroacetonitrile by hydrated electron (eaq–) produced in vacuum ultraviolet photolysis

Dichloroacetonitrile (DCAN) is one of the most toxic and common nitrogenous disinfection by-products in water treatment. It is necessary to understand how this compound can be removed. In this study, the effectiveness of vacuum ultraviolet (VUV) at 185 nm was evaluated to destroy DCAN. When water is exposed to VUV, hydroxyl radicals (HO•), hydrogen atoms (H•), and hydrated electrons (eaq−) are generated. The individual contributions of these reactive species to DCAN degradation were distinguished using multiple scavengers. The results showed that eaq– was the most important species for DCAN degradation. The second-order rate constant for eaq– reacting with DCAN was calculated to be 3.16 × 1010 M−1s−1 using a quantitative structure-activity relationship (QSAR) method adopted from previous study, and determined to be 3.76 (±0.02) × 1010 M−1s−1 by competition kinetics. Although dissolved oxygen (DO) at 8 mg/L consumed 86% eaq−, the rest of eaq− still led to 93% removal of DCAN within 20 min. Chloride was the major inorganic product of DCAN degradation, while nitrate and nitrite were minor products. Quantum chemical calculation and mass balance calculation under an oxygen free condition further suggested that cleavage of C–Cl bonds was the major pathway by eaq– attack. This study demonstrated the significant role of eaq– in micropollutant destruction during VUV treatment.

Two Chemometric Models for Cyclobenzaprine·HCl Determination in Presence of its Two Major Oxidative Degradation Products

Two validated, accurate and selective chemometric models were developed to detect cyclobenzaprine·HCl (CZ) in the presence of its two major degradation products: dibenzocycloheptatrienone and anthraquinone. Additionally, a comparative study was conducted between two chemometric models, namely partial least squares regression (PLSR) and spectral residual augmented classical least squares (SRACLS) via handling UV spectra in the range of 210–340 nm. A 3 factor 4 level experimental design was applied to provide a training set of 16 mixtures. An independent test set consisting of 9 mixtures was established to confirm the prediction capacity of the developed models. The results ascertain the capability of developed multivariate calibration models to selectively determine CZ with high selectivity and accuracy (100.0 ± 0.7% and 100.0 ± 0.6% for PLSR and SRACLS, respectively). A statistical comparison between the obtained results and results from the official HPLC method was run, where no significant difference was found.

Retention of Some Radionuclides on Soil in Site Selection for Nuclear Facility

The mobility of several radionuclides in a soil sample from a potential site in Egypt is examined. The retention of 152,154Eu (as homologs of 241Am), 60Co, 137Cs, and 99Mo in the presence of chelating ligands in the soil sample and without them is studied. Four chelating agents, namely, ethylenediaminetetraacetic acid (EDTA), citric and oxalic acids (as the major degradation products of EDTA), and humic acid are chosen for this purpose. The radionuclide retention on the soil without chelating ligands decreases in the order Co(II) > Eu(III) > Cs(I) > Mo(VI), with Kd equal to 11.38 mL/g for 99Mo and 1088 mL/g for 152,154Eu. The chelating ligands had little influence on the sorption of 60Co and 137Cs, but significantly decreased the retention of 152,154Eu owing to complexation. The soil sample on the potential nuclear site can act as a material for trapping the released radionuclides.

Forced degradation studies of norepinephrine and epinephrine from dental anesthetics: Development of stability‐indicating HPLC method and in silico toxicity evaluation

Injectable solutions containing epinephrine (EPI) and norepinephrine (NE) are not stable, and their degradation is favored mainly by the oxidation of catechol moiety. As studies of these drugs under forced degradation conditions are scarce, herein, we report the identification of their degradation products (DP) in anesthetic formulations by the development of stability-indicating HPLC method. Finally, the risk assessment of the major degradation products was evaluated using in silico toxicity approach. HPLC method was developed to obtain a higher selectivity allowing adequate elution for both drugs and their DPs. The optimized conditions were developed using a C18 HPLC column, sodium 1-octanesulfonate, and methanol (80:20, v/v) as mobile phase, with a flow rate of 1.5 mL/min, UV detection at 199 nm. The analysis of standard solutions with these modifications resulted in greater retention time for EPI and NE, which allow the separation of these drugs from their respective DPs. Then, five DPs were identified and analyzed by in silico studies. Most of the DPs showed important alerts as hepatotoxicity and mutagenicity. To the best of our acknowledgment, this is the first report of a stability-indicating HPLC method that can be used with formulations containing catecholamines.

Insights into the degradation chemistry of tazarotene, a third generation acetylenic retinoid: LC-HRMS (Orbitrap), LC-MSn and NMR characterization of its degradation products, and prediction of their physicochemical and ADMET properties

Tazarotene is a prodrug that belongs to the acetylenic class of retinoids. The drug was subjected to hydrolytic, oxidative and photolytic stress testing to establish its comprehensive degradation chemistry. The drug proved to be unstable under acidic and basic hydrolytic conditions, yielding tazarotenic acid, which is a known major degradation product (DP) and an active metabolite. Additionally, two DPs each were generated upon interaction of drug and tazarotenic acid with HCl, used as an acid stressor. These were experimentally proven as pseudo DPs, as they did not originate when H2SO4 was employed as the stressor. The drug was also unstable under oxidative and photolytic conditions, yielding six DPs. All the products were separated on reversed phase (C18) column, using mobile phase composed of 10 mM ammonium formate (pH 3.5) and acetonitrile, which was run in a gradient mode. The separated DPs were subjected to LC-HRMS and LC-MSn studies for their initial characterization. Seven hydrolytic and oxidative DPs that could be isolated using semi-preparative column were subjected to extensive 1D (1H, 13C and DEPT-135) and 2D (COSY, HSQC and HMBC) NMR studies to confirm their structures. In total, five novel DPs were characterized, apart from two previously reported DPs, viz., tazarotenic acid and tazarotene sulfoxide, and four additional pseudo DPs. The complete degradation pathway of the drug was established. In silico ADMET properties of the drug and its DPs were evaluated using ADMET Predictor™.

A novel hydrophilic interaction liquid chromatography method for the analysis of arterolane; Isolation and structural elucidation of its major degradation product by LC-HRMS and NMR

Adequate retention of arterolane (ART) has not been published in the literature till date; the hydrophilic interaction liquid chromatographic (HILIC) method with improved retention and separation of arterolane from its degradation products are reporting here for the first time. The present study discusses the comparative retention of the drug-using Reverse Phase C18 and HILIC columns, indicating the effective method (Syncronis HILIC-150 x 4.6 mm, 5μ). It was observed that the buffer concentration (ammonium acetate) in the mobile phase plays a crucial role in the retention of ART. Forced degradation studies of ART were conducted as per ICH Q1 (R2) prescribed conditions. The drug is not stable in hydrolytic (acid, base and neutral), oxidative and photolytic conditions and observed four unique degradation products (DPs). The optimized method for the analysis of degraded samples comprises of Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) technique having Agilent HILIC plus (100 × 4.6 mm, 3.5μ) column and acetonitrile (ACN) and 10 mM ammonium acetate 75:25 (% v/v) mobile phase with 0.4 mL/minute flow. Initially, the structure of all four DPs was proposed on the basis of accurate mass and their fragmentation pattern. The major degradation product (DP4) was isolated, and its structure was confirmed by HRMS and 1H NMR, 13C NMR, HMBC, DEPT 135 and Deuteriated NMR spectroscopy. The formation of DPs might be due to the breakdown of (1 r,3r,5 r,7r)-2-methoxyadamantan-2-ol from ART (DP4), and subsequent diol formation at 1,2,4-trioxolane moiety (DP3).

Preformulation studies of l-glutathione: physicochemical properties, degradation kinetics, and in vitro cytotoxicity investigations

Objectives: l-Glutathione (GSH) is an endogenous tripeptide with super antioxidant properties. In this study, preformulation parameters of GSH and its degradation products were fully investigated.Significance: To date, no experimental preformulation data is available for GSH. Therefore, to the author’s knowledge, this is the first study to experimentally determine the preformulation parameters of GSH, which can be considered more reliable for further studies.Methods: An HPLC method for GSH was optimized and validated to accurately quantify the GSH amount in solution, used to investigate GSH’s solubility and Log P. Differential Scanning Calorimeter and Thermogravimetric Analyzer were used to evaluate the thermal properties of GSH. Polarized microscope and Fourier-transform Infrared Spectroscopy were used to determine GSH’s crystal habits and functional groups, respectively. Forced degradation kinetics and the degradation products were investigated and identified by LC-MS, respectively. GSH’s cellular cytotoxicity on fibroblasts was investigated by MTT assay.Results: It was determined that GSH has high aqueous solubility (252.7 mg/mL), low Log P (−3.1), a melting endotherm of 195 °C and decomposition at 210°C, negligible moisture content, and a rectangular/cylindrical-shaped crystalline form. Seven degradation products were identified; one of the major degradation products of GSH under different conditions is first order kinetic oxidation into glutathione disulfide. No cytotoxicity was observed when fibroblasts were treated with GSH (0.005–10.000 mg/mL).Conclusions: Precise preformulation parameters of GSH were obtained, and these are imperative for the development and optimization of advanced GSH formulations.

Experimental and DFT studies on complexation of uranyl with N-(2-Hydroxyethyl)iminodiacetic acid in aqueous medium

The nuclear decontaminating agents such as ethylenediamminetetraacetic acid (EDTA), picolinic acid, nitrilotriacetic acid (NTA) and citric acid are co-disposed with the nuclear waste at the storage sites. The thermal, catalytic and radiolytic degradation of this organic waste results in the formation of N-(2-Hydroxyethyl)iminodiacetic acid (HEIDA-H2) as one of the major degradation product. The knowledge on chemical speciation and aqueous thermodynamics of radionuclides in presence of organic chelates is a key input to the codes for framing safe and strategic disposal of radioactive waste. Present work aimed at the determination of thermodynamic parameters (log K, ΔG, ΔH and ΔS), speciation diagram, spectroscopic properties and structural analysis for UO22+-HEIDA complexes in aqueous solution. UO22+ forms ML and ML2 type of species with HEIDA as determined by potentiometry and further corroborated by absorption and luminescence spectroscopy. The Electrospray ionization mass spectrometry (ESI-MS) studies also identified the ML and ML2 complexes. In addition, the difference in the complexation behavior of UO22+ with HEIDA and IDA; which differ by hydroxyethyl substitution on imino nitrogen is explained on the basis of thermodynamic parameters. The 1:1 UO22+-HEIDA complex is exothermic formation while the 1:1 UO22+-IDA complexes are endothermic formations. The differences in enthalpy and entropy of formations are interpreted to reveal the role of hydroxyethyl group on UO22+- HEIDA complexation. NMR studies are carried to elucidate the structures of 1:1 and 1:2 UO22+-HEIDA complexes. The comparison of log K values with structurally similar ligands and NMR spectroscopic studies suggested the tridentate nature for HEIDA. The hydroxyethyl group was found to be uncoordinated with UO22+. The theoretical studies showed the indirect participation of hydroxyethyl group on complexation by charge polarization and by steric influence on coordinating groups.

EFFECT OF ELECTROLYZED REDUCING WATER WITH VARIOUS CONCENTRATION ON CARBENDAZIM FUNGICIDE REMOVAL IN CHERRY TOMATO

The effect of electrolyzed reducing water (ER) on a degradation of carbendazim residues degradation of cherry tomato (Solanum lycopersicum L. var. cerasiforme) was investigated. Electrolyzed water was generated by electrolysis from 5% NaCl solution. The cherry tomato samples were washed in ER water at different concentrations (100, 250, 500 and 1000 mg/L) and in distilled water (control). The standard carbendazim solution (5 mg/L) was treated with the previous concentrations of ER. Reduction of residual carbendazim was determined by high performance liquid chromatography (HPLC) while liquid chromatography-quadrupole-timeof-flight mass spectrometer (Agilent, LC-6545 Q-TOF/MS) was used to determine the concentration of anions as major degradation products. It was found that all concentration of ER water significantly reduced carbendazim solution, compared to control. The ER water at 250 mg/L could effectively remove carbendazim residues from cherry tomato, most of the degradation occurred within 30 min. Residue of carbendazim on cherry tomato were reduced by 60.36%, 80.49%, 67.32%, and 64.68% after 30 min washing in ER 100 mg/L, 250 mg/L, 500 mg/L, and 1000 mg/L, respectively.

Monitoring of methylglyoxal/indole interaction by ATR-FTIR spectroscopy and qTOF/MS/MS analysis

Sugar derived reactive 1,2-dicarbonyl intermediates are considered important precursors for the formation of Maillard reaction products. Efficient strategies are needed to modulate their formation in food. Indole a major thermal degradation product of tryptophan, has been shown to scavenge such 1,2-dicarbonyls at high temperatures. In this study, the trapping of methylglyoxal by indole was monitored at various temperatures either by (a) ATR-FTIR spectroscopy or (b) in-solution using qTOF/MS/MS analysis. Information obtained through these studies have indicated that even at room temperature indole can quickly react with methylglyoxal forming an adduct as confirmed by the emergence of a new peak at 1729 cm−1 and by qTOF/MS/MS analysis. On the open surface of the ATR crystal this adduct underwent a fast oxidization into carboxylic acid as evidenced by the disappearance of the band at 1729 cm−1 and the formation of a new band at 1712 cm−1 and its subsequent conversion into a carboxylate band under basic conditions.