Investigations of Major α-Dicarbonyl Content in U.S. Honey of Different Geographical Origins.

α-Dicarbonyls are significant degradation products resulting from the Maillard reaction during food processing. Their presence in foods can indicate the extent of heat exposure, processing treatments, and storage conditions. Moreover, they may be useful in providing insights into the potential antibacterial and antioxidant activity of U.S. honey. Despite their importance, the occurrence of α-dicarbonyls in honey produced in the United States has not been extensively studied. This study aims to assess the concentrations of α-dicarbonyls in honey samples from different regions across the United States. The identification and quantification of α-dicarbonyls were conducted using reverse-phase liquid chromatography after derivatization with o-phenylenediamine (OPD) and detected using ultraviolet (UV) and mass spectrometry methods. This study investigated the effects of pH, color, and derivatization reagent on the presence of α-dicarbonyls in honey. The quantification method was validated by estimating the linearity, precision, recovery, method limit of detection, and quantification using known standards for GO, MGO, and 3-DG, respectively. Three major OPD-derivatized α-dicarbonyls including methylglyoxal (MGO), glyoxal (GO), and 3-deoxyglucosone (3-DG), were quantified in all the honey samples. 3-Deoxyglucosone (3-DG) was identified as the predominant α-dicarbonyl in all the U.S. honey samples, with concentrations ranging from 10.80 to 50.24 mg/kg. The total α-dicarbonyl content ranged from 16.81 to 55.74 mg/kg, with the highest concentration measured for Southern California honey. Our results showed no significant correlation between the total α-dicarbonyl content and the measured pH solutions. Similarly, we found that lower amounts of the OPD reagent are optimal for efficient derivatization of MGO, GO, and 3-DG in honey. Our results also indicated that darker types of honey may contain higher α-dicarbonyl content compared with lighter ones. The method validation results yielded excellent recovery rates for 3-DG (82.5%), MGO (75.8%), and GO (67.0%). The method demonstrated high linearity with a limit of detection (LOD) and limit of quantitation (LOQ) ranging from 0.0015 to 0.002 mg/kg and 0.005 to 0.008 mg/kg, respectively. Our results provide insights into the occurrence and concentrations of α-dicarbonyl compounds in U.S. honey varieties, offering valuable information on their quality and susceptibility to thermal processing effects.

Amination and crosslinking of acetone-fractionated hardwood kraft lignin using different amines and aldehydes for sustainable bio-based wood adhesives.

Hardwood kraft lignin from the pulping industry is burned or discarded. Its valorization was conducted by subjecting fractionation, amination with ethylenediamine, diethylenetriamine, and monoethanolamine, and crosslinking with formaldehyde or glyoxal to obtain bio-based wood adhesives. Acetone-soluble and insoluble hardwood kraft lignin were prepared and subjected to amination and then crosslinking. Fourier transform infrared, 13C NMR, 15N NMR, and X-ray photoelectron spectroscopy results revealed successful amination with amide, imine, and ether bonds and crosslinking of all samples. Hardwood kraft lignin aminated with diethylenetriamine/ethylenediamine and crosslinked using glyoxal exhibited excellent results in comparison with samples crosslinked using formaldehyde. Acetone-insoluble hardwood kraft lignin aminated and crosslinked using diethylenetriamine and formaldehyde, respectively, exhibited excellent adhesion strength with plywood, satisfying the requirements of the Korean standards. The amination and crosslinking of industrial waste hardwood kraft lignin constitute a beneficial valorization method.

Scavenging Glyoxal and Methylglyoxal by Synephrine and Neohesperidin from Flowers of Citrus aurantium L. var. amara Engl. in Mice and Humans.

There is considerable research evidence that α-dicarbonyl compounds, including glyoxal (GO) and methylglyoxal (MGO), are closely related to many chronic diseases. In this work, after comparison of the capture capacity, reaction pathway, and reaction rate of synephrine (SYN) and neohesperidin (NEO) on GO/MGO in vitro, experimental mice were administrated with SYN and NEO alone and in combination. Quantitative data from UHPLC-QQQ-MS/MS revealed that SYN/NEO/HES (hesperetin, the metabolite of NEO) could form the GO/MGO-adducts in mice (except SYN-MGO), and the levels of GO/MGO-adducts in mouse urine and fecal samples were dose-dependent. Moreover, SYN and NEO had a synergistic scavenging effect on GO in vivo by promoting each other to form more GO adducts, while SYN could promote NEO to form more MGO-adducts, although it could not form MGO-adducts. Additionally, human experiments showed that the GO/MGO-adducts of SYN/NEO/HES found in mice were also detected in human urine and fecal samples after drinking flowers of Citrus aurantium L. var. amara Engl. (FCAVA) tea using UHPLC-QTOF-MS/MS. These findings provide a novel strategy to reduce endogenous GO/MGO via the consumption of dietary FCAVA rich in SYN and NEO.

Identification of redox activators for continuous reactivation of glyoxal oxidase from Trametes versicolor in a two-enzyme reaction cascade.

Glyoxal oxidases, belonging to the group of copper radical oxidases (CROs), oxidize aldehydes to carboxylic acids, while reducing O2 to H2O2. Their activity on furan derivatives like 5-hydroxymethylfurfural (HMF) makes these enzymes promising biocatalysts for the environmentally friendly synthesis of the bioplastics precursor 2,5-furandicarboxylic acid (FDCA). However, glyoxal oxidases suffer from inactivation, which requires the identification of suitable redox activators for efficient substrate conversion. Furthermore, only a few glyoxal oxidases have been expressed and characterized so far. Here, we report on a new glyoxal oxidase from Trametes versicolor (TvGLOX) that was expressed at high levels in Pichia pastoris (reclassified as Komagataella phaffii). TvGLOX was found to catalyze the oxidation of aldehyde groups in glyoxylic acid, methyl glyoxal, HMF, 2,5-diformylfuran (DFF) and 5-formyl-2-furancarboxylic acid (FFCA), but barely accepted alcohol groups as in 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), preventing formation of FDCA from HMF. Various redox activators were tested for TvGLOX reactivation during catalyzed reactions. Among them, a combination of horseradish peroxidase and its substrate 2,2'-azino-di-(3-ethylbenzthiazoline sulfonic acid) (ABTS) most efficiently reactivated TvGLOX. Through continuous reactivation of TvGLOX in a two-enzyme system employing a recombinant Moesziomyces antarcticus aryl-alcohol oxidase (MaAAO) almost complete conversion of 8 mM HMF to FDCA was achieved within 24 h.

Scavenging Glyoxal and Methylglyoxal by Synephrine Alone or in Combination with Neohesperidin at High Temperatures.

α-Dicarbonyl compounds, such as glyoxal (GO) and methylglyoxal (MGO), are a series of chemical hazards that exist in vivo and in vitro, posing a threat to human health. We aimed to explore the scavenging effects on GO/MGO by synephrine (SYN) alone or in combination with neohesperidin (NEO). First, through LC-MS/MS, we confirmed that both SYN and NEO could effectively remove GO and form GO adducts, while NEO could also clear MGO by forming MGO adducts, and its ability to clear MGO was stronger than that of GO. Second, a synergistic inhibitory effect on GO was found when SYN and NEO were used in combination by using the Chou-Talalay method; on the other hand, SYN could promote NEO to clear more MGO, although SYN could not capture MGO. Third, after synthesizing four GO/MGO-adducts (SYN-GO-1, SYN-GO-3, NEO-GO-7, and NEO-MGO-2) and identifying their structure through NMR, strict correlations between the GO/MGO-adducts and the GO/MGO-clearance rate were found when using SYN and NEO alone or in combination. Furthermore, it was inferred that the synergistic effect between SYN and NEO stems from their mutual promotion in capturing more GO by the quantitative analysis of the adducts in the combined model. Finally, a study was conducted on flowers of Citrus aurantium L. var. amara Engl. (FCAVA, an edible tea) rich in SYN and NEO, which could serve as an effective GO and MGO scavenger in the presence of both GO and MGO. Therefore, our study provided well-defined evidence that SYN and NEO, alone or in combination, could efficiently scavenge GO/MGO at high temperatures, whether in the pure form or located in FCAVA.

Phenotypic and genome-wide studies on dicarbonyls: major associations to glomerular filtration rate and gamma-glutamyltransferase activity.

BACKGROUND: The dicarbonyl compounds methylglyoxal (MG), glyoxal (GO) and 3-deoxyglucosone (3-DG) have been linked to various diseases. However, disease-independent phenotypic and genotypic association studies with phenome-wide and genome-wide reach, respectively, have not been provided. METHODS: MG, GO and 3-DG were measured by LC-MS in 1304 serum samples of two populations (KORA, n = 482; BiDirect, n = 822) and assessed for associations with genome-wide SNPs (GWAS) and with phenome-wide traits. Redundancy analysis (RDA) was used to identify major independent trait associations. FINDINGS: Mutual correlations of dicarbonyls were highly significant, being stronger between MG and GO (ρ = 0.6) than between 3-DG and MG or GO (ρ = 0.4). Significant phenotypic results included associations of all dicarbonyls with sex, waist-to-hip ratio, glomerular filtration rate (GFR), gamma-glutamyltransferase (GGT), and hypertension, of MG and GO with age and C-reactive protein, of GO and 3-DG with glucose and antidiabetics, of MG with contraceptives, of GO with ferritin, and of 3-DG with smoking. RDA revealed GFR, GGT and, in case of 3-DG, glucose as major contributors to dicarbonyl variance. GWAS did not identify genome-wide significant loci. SNPs previously associated with glyoxalase activity did not reach nominal significance. When multiple testing was restricted to the lead SNPs of GWASs on the traits selected by RDA, 3-DG was found to be associated (p = 2.3 × 10-5) with rs1741177, an eQTL of NF-κB inhibitor NFKBIA. INTERPRETATION: This large-scale, population-based study has identified numerous associations, with GFR and GGT being of pivotal importance, providing unbiased perspectives on dicarbonyls beyond the current state. FUNDING: Deutsche Forschungsgemeinschaft, Helmholtz Munich, German Centre for Cardiovascular Research (DZHK), German Federal Ministry of Research and Education (BMBF).

Contents of ɑ-dicarbonyl compounds in commercial black tea and affected by the processing.

The species and contents of ɑ-dicarbonyls in commercial black tea were examined, along with the effects of the manufacturing process and drying temperature on the formation of ɑ-dicarbonyls. Ten ɑ-dicarbonyls were quantified in commercial and in-process black tea samples by using UPLC-MS/MS and their derived quinoxalines. The ɑ-dicarbonyls content in commercial black tea decreased significantly (p < 0.05) in the following order: 3-deoxyglucosone > glucosone > 3-deoxypentosone = threosone > galactosone ≥ methylglyoxal = glyoxal ≥ 3-deoxygalactosone = 3-deoxythreosone = diacetyl. Except for 3-deoxyglucosone and 3-deoxygalactosone, a further eight ɑ-dicarbonyls were identified in all manufacturing steps of black tea. Except for the drying step, the rolling and fermenting played important roles in the formation of ɑ-dicarbonyls. The total contents of ɑ-dicarbonyls in black tea infusion ranged from 16.48 to 75.32 µg/g based on our detected ten ɑ-dicarbonyls.

Bi-functionality of glyoxal caged nucleic acid coupled with CRISPR/Cas12a system for Hg2+ determination.

A highly sensitive and selective fluorescence method has been conducted for the detection of Hg2+ based on aminophenylboronic acid-modified carboxyl magnetic beads (CMB@APBA) and CRISPR/Cas12a system mediated by glyoxal caged nucleic acid (gcDNA). As a bi-functional DNA linker, gcDNA offers advantages of simultaneous recognition by boronic acid and complementary DNA/RNA. Under acidic condition, gcDNA can be immobilized on CMB@APBA through the formation of borate ester bond. The formed boric acid-esterified gcDNA can further bind with complementary CRISPR RNA through A-T base pairing to activate Cas12a with kcat/Km ratio of 3.4 × 107 s-1 M-1, allowing for amplified signal. Hg2+ can specifically combine with CMB@APBA, resulting in the release of gcDNA from CMB@APBA and the following inhibition on the activation of CRISPR/Cas12a system around magnetic bead. Under optimal conditions, the method exhibits a linear range from 20 to 250 nM, with a detection limit of 2.72 nM. The proposed method can detect Hg2+ in milk and tea beverages, providing a great significance for on-site monitoring of Hg2+ contamination in food.

Peptide Stapling by Crosslinking Two Amines with α-Ketoaldehydes through Diverse Modified Glyoxal-Lysine Dimer Linkers.

α-Ketoaldehydes play versatile roles in the ubiquitous natural processes of protein glycation. However, leveraging the reactivity of α-ketoaldehydes for biomedical applications has been challenging. Previously, the reactivity of α-ketoaldehydes with guanidine has been harnessed to design probes for labeling Arg residues on proteins in an aqueous medium. Herein, a highly effective, broadly applicable, and operationally simple protocol for stapling native peptides by crosslinking two amino groups through diverse imidazolium linkers with various α-ketoaldehyde reagents is described. The use of hexafluoroisopropanol as a solvent facilitates rapid and clean reactions under mild conditions and enables unique selectivity for Lys over Arg. The naturally occurring GOLD/MOLD linkers have been expanded to encompass a wide range of modified glyoxal-lysine dimer (OLD) linkers. In a proof-of-concept trial, these modular stapling reactions enabled a convenient two-round strategy to streamline the structure-activity relationship (SAR) study of the wasp venom peptide anoplin, leading to enhanced biological activities.

Defining an Optimized Workflow for Enriching and Analyzing Residual Tumor Populations Using Intracellular Markers.

Tumor relapse is well recognized to arise from treatment-resistant residual populations. Strategies enriching such populations for in-depth downstream analyses focus on tumor-specific surface markers; however, enrichment using intracellular biomarkers remains challenging. Using B-cell lymphoma as an exemplar, we demonstrate feasibility to enrich B-cell lymphoma 2 (BCL2)high populations, a surrogate marker for t(14;18)+ lymphomas, for use in downstream applications. Different fixation protocols were assessed for impact on antibody expression and RNA integrity; glyoxal fixation demonstrated superior results regarding minimal effects on surface and intracellular expression, and RNA quality, compared with alternative fixatives evaluated. Furthermore, t(14;18)+ B cells were effectively detected using intracellular BCL2 overexpression to facilitate tumor cell enrichment. Tumor cell populations were enriched using the cellenONE F1.4 single-cell sorting platform, which detected and dispensed BCL2high-expressing cells directly into library preparation reagents for transcriptome analyses. Sorted glyoxal-fixed cells generated good quality sequencing libraries, with high concordance between live and fixed single-cell transcriptomic profiles, discriminating cell populations predominantly on B-cell biology. Overall, we successfully developed a proof-of-concept workflow employing a robust cell preparation protocol for intracellular markers combined with cell enrichment using the cellenONE platform, providing an alternative to droplet-based technologies when cellular input is low or requires prior enrichment to detect rare populations. This workflow has wider prognostic and therapeutic potential to study residual cells in a pan-cancer setting.

Histochemical and morphological evaluation of a glyoxal acid-free fixative.

The application of most chemical fixatives, such as formalin, in the anatomic pathology laboratory requires safety training and hazardous chemical monitoring due to the toxicity and health risks associated with their use. Consequently, the use of formalin has been banned in most applications in Europe; the primary exception is its use in the histology laboratory in lieu of a suitable and safer alternative. Glyoxal based solutions, several of which are available commercially, are the most promising alternative fixatives, because they are based on a mechanism of fixation similar to that of formalin. Unlike formalin, however, glyoxal based solutions do not dissociate from water and therefore do not require ventilation measures such as a fume hood. A primary barrier to the adoption of commercially available glyoxal based solutions is their low pH, which can produce undesirable morphological and antigenic tissue alterations; however, a recently available neutral pH glyoxal product (glyoxal acid free) (GAF) has been developed to mitigate the challenges of low pH. We compared the morphology and histochemistry among tissues fixed in 10% neutral buffered formalin, a commercially available acidic glyoxal product (Prefer), and GAF. Tissues fixed in formalin and Prefer exhibited similar morphology and staining properties; tissues fixed with 2% GAF exhibited deleterious effects.

Contribution of Hydroxycinnamic Acids to Color Formation in Nonenzymatic Browning Reactions with Key Maillard Reaction Intermediates.

The Maillard reaction is a vital part of food processing, involving a vast number of complex reaction pathways, resulting in high-molecular-weight colorants. So far, studies have been focused on the conversion of carbohydrates and amino compounds, but the literature elaborating the contribution of phenolic compounds to the formation of the colored end-products is still rare. The aim of this study was to characterize early reactions, underlying the formation of phenol-containing melanoidins. For this purpose, binary model systems of the prominent phenolic compounds caffeic acid and ferulic acid combined with α-dicarbonyl compounds typically formed in the Maillard reaction such as glyoxal, methylglyoxal, and diacetyl were analyzed after heat treatment. High-resolution mass spectrometry revealed that decarboxylation, aromatic electrophilic substitution, and nucleophilic addition are important reaction steps that lead to colored heterogeneous oligomers. Polymerization was favored for phenolic compounds with a high electron density in the aromatic system and for α-dicarbonyl compounds carrying aldehyde functions.

Glyoxal-derived advanced glycation end products (GO-AGEs) with UVB critically induce skin inflammaging: in vitro and in silico approaches.

Advanced glycation end products (AGEs) have potential implications on several diseases including skin inflammation and aging. AGEs formation can be triggered by several factors such as UVB, glyoxal and methylglyoxal etc. However, little attention has been paid to glyoxal-derived AGEs (GO-AGEs) and UVB-induced skin inflammaging, with none have investigated together. This study aimed to investigate the possible role of GO-AGEs and UVB in skin inflammaging focusing on revealing its molecular mechanisms. The effects of GO-AGEs in the presence or absence of UVB were studied by using enzyme linked immunosorbent assay, western blotting, qPCR, flow cytometry and in silico approaches. In HaCaT cells, GO-AGEs in the presence of UVB irradiation (125 mJ/cm2) dramatically enhanced the release of different pro-inflammatory cytokines (IL-1ß, IL-6, and TNF-α) with further activation of RAGE signaling pathways (NF-κB, COX 2, and IL- 1ß) and increased oxidative stress also noticed in NHEK cells. In NHDF cells, extracellular matrix disruption noted via increasing matrix metalloproteinase release and decreasing collagen type 1 and SIRT1 expression. Besides that, the docking scores obtained from the molecular docking study support the above-mentioned results. This study strongly suggests the pivotal role of GO-AGEs in skin inflammaging and illuminates novel molecular pathways for searching most effective and updated anti-aging therapy.

Glyoxal in Foods: Formation, Metabolism, Health Hazards, and Its Control Strategies.

Glyoxal is a highly reactive aldehyde widely present in common diet and environment and inevitably generated through various metabolic pathways in vivo. Glyoxal is easily produced in diets high in carbohydrates and fats via the Maillard reaction, carbohydrate autoxidation, and lipid peroxidation, etc. This leads to dietary intake being a major source of exogenous exposure. Exposure to glyoxal has been positively associated with a number of metabolic diseases, such as diabetes mellitus, atherosclerosis, and Alzheimer's disease. It has been demonstrated that polyphenols, probiotics, hydrocolloids, and amino acids can reduce the content of glyoxal in foods via different mechanisms, thus reducing the risk of exogenous exposure to glyoxal and alleviating carbonyl stresses in the human body. This review discussed the formation and metabolism of glyoxal, its health hazards, and the strategies to reduce such health hazards. Future investigation of glyoxal from different perspectives is also discussed.

Comparison of the properties of phenolic resin synthesized from different aldehydes and evaluation of the release and health risks of VOCs.

Different amounts of glyoxal and paraformaldehyde were used to synthesize phenol-glyoxal (PG) and phenol-paraformaldehyde (PPF) resins, which were compared with conventional phenol-formaldehyde (PF) resins. Glyoxal oxidation leads to a pH value of 9.83 for PG 2.2. With the addition of polyformaldehyde, PPF 2.2 exhibited the highest viscosity at 17333.33 mPa s. The PPF 2.0 plywood has a maximum bonding strength of 1.94 MPa. The formaldehyde emission of PG 1.8 plywood is found to have a minimum value of 0.025 mg/m3, reaching the ENF limit (≤0.025 mg/m3). Acetaldehyde is found only in volatile organic compound (VOC) emissions from PG plywood and is associated with increased glyoxal. PPF plywood emitted more aromatic and total VOC (TVOC) than the other two plywood types. The measured TVOC for PPF 2.2 is 196.07 µg/m3. The results showed that the total cancer risk (TCR) values of PPF 1.8, PPF 2.0, and PG 1.8 were above the threshold of 1.00E-4, indicating a definite carcinogenic risk. Acetaldehyde in the PG plywood exceeded the safety threshold for noncarcinogenic risk. The use of paraformaldehyde in the wood-based panel production is been considered a possible means of improving the bonding strength of plywood. Glyoxal has also been shown to be a viable method for lowering the formaldehyde emissions from plywood. The VOC emissions from plywood changed significantly depending on the aldehyde used. Limiting VOCs that present high health hazards is crucial for reducing the negative impact of plywood on both indoor environments and human health.

Simultaneous determination of carbonyl compounds related to thermal treatment and oxidative stability of infant formulas by gas-diffusion microextraction and high-performance liquid chromatography with ultraviolet detection.

Infant formulae are the only possible alternative to breastfeeding during the first year of life, so it is crucial to assure their innocuousness. Infant formula undergoes heat treatments to ensure safety and shelf life. However, such processes impact health as they lead to the formation of malondialdehyde, acrolein, and α-dicarbonyl compounds, related to Maillard reaction. Thus, there is a need for improved analytical methods to ensure the safety, quality, and nutritional value of infant formulae, and also exploring the potential of specific compounds as indicators for quality control and monitoring purposes. We developed and validated a novel, efficient, and cost-effective method using gas-diffusion microextraction for the simultaneous quantification of carbonyl compounds in infant formula. Malondialdehyde, acrolein, glyoxal, methylglyoxal, and diacetyl were detected as o-phenylenediamine derivatives using HPLC with UV detection. Parameters influencing extraction efficiency were studied using an asymmetric screening design. The validated method has shown excellent linearity, sensitivity, accuracy, and precision. It was applied to analyze 26 infant formula samples, including starter, follow-up, and special formulated powdered infant formula. Methylglyoxal was found in all samples (0.201-3.153 µg mL-1), while malondialdehyde was present only in certain starter formulas (1.033-1.802 µg mL-1). Acrolein (0.510-3.246 µg mL-1), glyoxal (0.109-1.253 µg mL-1), and diacetyl (0.119-2.001 µg mL-1) were detected in various sample types. Principal components and hierarchical cluster analyses have showcased distinct sample clustering based on analyte contents. This study presents a novel methodology for the analysis of markers of thermal treatment and oxidative stability in infant formula. It contributes to the characterization of the products' composition and quality control of infant formulae, thereby enhancing their safety and nutritional adequacy. This study also presents the first reported quantification of acrolein in infant formula and introduces the application of the acrolein-o-phenylenediamine derivative for food analysis.

pH-Dependent Aqueous-Phase Brown Carbon Formation: Rate Constants and Implications for Solar Absorption and Atmospheric Photochemistry.

Aqueous-phase reactions of α-dicarbonyls with amines or ammonium have been identified as important sources of secondary brown carbon (BrC). However, the kinetics of BrC formation and the effects of pH are still not very clear. In this study, the kinetics of BrC formation by aqueous reactions of α-dicarbonyls (glyoxal and methylglyoxal) with ammonium, amino acids, or alkylamines in bulk solution at different pH values are investigated. Our results reveal pH-parameterized BrC production rate constants, kBrCII (m-1 [M]-2 s-1), based on the light absorption between 300 and 500 nm: log10(kBrCII) = (1.0 ± 0.1) × pH - (7.4 ± 1.0) for reactions with glyoxal and log10(kBrCII) = (1.0 ± 0.1) × pH - (6.3 ± 0.9) for reactions with methylglyoxal. The linear slopes closing to 1.0 indicate that BrC formation is governed by the nitrogen nucleophilic addition pathway. Consequently, the absorptivities of the produced BrC increase exponentially with the increase of pH. BrC from reactions with methylglyoxal at higher pH (≥6.5) exhibits optical properties comparable to BrC from biomass burning or coal combustion, categorized as the "weakly" absorbing BrC, while BrC from reactions with methylglyoxal at lower pH (<6.0) or reactions with glyoxal (pH 5.0-7.0) falls into the "very weakly" absorbing BrC. The pH-dependent BrC feature significantly affects the solar absorption ability of the produced BrC and thus the atmospheric photochemical processes, e.g., BrC produced at pH 7.0 absorbs 14-16 times more solar power compared to that at pH 5.0, which in turn could lead to a decrease of 1 order of magnitude in the photolysis rate constants of O3 and NO2.

Mechanochemistry of Strecker degradation: Interaction of glyoxal with amino acids.

Mechanochemistry is rapidly evolving into a versatile and green method for chemical synthesis. Due to its unique reaction conditions, ball milling of sugars and amino acids mainly leads to the formation of Amadori products with minimum degradation. In this study, we milled glyoxal trimer dihydrate with twenty proteogenic amino acids to demonstrate the formation of Strecker degradation products. HS-GC/MS studies indicated that Strecker degradation proceeded to selectively generate Strecker aldehyde and unsubstituted pyrazine as the major volatiles. Moreover, ESI/qToF/MS studies demonstrated for the first time the formation of the proposed key Strecker degradation intermediates, such as the condensation products and their decarboxylated products, indicating the similarity of the mechanism of Strecker reaction under ball milling to that proposed under hydrothermal reaction conditions. These studies provided supporting evidence that ball milling at ambient temperatures could be used as a novel synthetic approach to prepare precursors of aroma-active volatiles through Strecker degradation.

Organically modified montmorillonite composited with magnetic glyoxal-chitosan Schiff base for reactive blue 19 dye removal: Process optimization and adsorptive mechanism.

In this study, a new biocomposite magnetic adsorbent (magnetic glyoxal-chitosan Schiff base/organically modified montmorillonite (MCTS-GOX/OMMT)) was synthesized and employed for the adsorption of reactive blue 19 dye (RB19) from aqueous environment. The physicochemical properties of the MCTS-GOX/OMMT were confirmed by using various characterization techniques such as BET, XRD, FTIR, SEM-EDX, VSM, and pHpzc. The adsorption key variables were statistically optimized via Box-Behnken design (BBD) And accordingly the best operational conditions to achieve maximum RB19 removal were recorded at MCTS-GOX/OMMT dosage = 0.1 g/0.1 L, solution pH = 4, and working temperature = 25 °C. The adsorption process for RB19 appeared to follow the pseudo-second-order kinetic and the Langmuir isotherm models, according to the findings of the adsorption kinetics and equilibrium investigations. The maximum adsorption capacity of the MCTS-GOX/OMMT towards RB19 was 122.3 mg/g, demonstrating its preferable adsorption capability. The successful development of this novel magnetic bioadsorbent with excellent adsorption ability towards organic dyes and efficient separation ability opens possibilities for its practical application in wastewater treatment and dye removal processes.

Alginate-modified surfactants functionalized metal-organic framework-based fluorescent film sensors for detection and adsorption of volatile aldehydes in water.

Volatile aldehydes have an adverse impact on both human health and the environment, therefore, a fast, straightforward, highly accurate detection technique for the simultaneous detection and removal of several aldehydes is eagerly anticipated. Herein, novel APGF@ZIF-8 and APOF@ZIF-8 sensing materials were developed by coating fluorescent alginate-modified surfactants (APGF and APOF) into the ZIF-8 MOFs to produce quite porous fluorescent sensors (SBET up to 1519 m2/g). The detection capacity of the prepared sensors for benzaldehyde, glyoxal, formaldehyde, and acetaldehyde has been examined. The detection mechanism was suggested as hydrogen bonding formation between the sensors and volatile aldehydes as confirmed by Gaussian calculations. All the fluorescence spectra of aldehydes display remarkable linear detection relationships in the range of 0.05-200 µM with the limits of detection (LOD) values in the range of 0.001-0.18 µM (0.106-10.44 ppb). These sensors were utilized successfully to detect multiple volatile aldehydes in river water samples with satisfactory recoveries of 96-107 %. Interestingly, fluorescent APGF@ZIF-8/CS and APOF@ZIF-8/CS films as portable disposable removal techniques for benzaldehyde, glyoxal, formaldehyde, and acetaldehyde from water were fabricated. APOF@ZIF-8/CS exhibited an excellent formaldehyde adsorption capacity of 58.30 mg/g and an adsorption removal efficiency of 93.5 %. The adsorption process of biosorbent on various aldehydes was fitted by Freundlich adsorption isotherm. The adsorption kinetics followed Pseudo-second-order kinetic model.