Investigation of reactive alpha-dicarbonyl compounds generated from the Maillard reactions of L-methionine with reducing sugars via their stable quinoxaline derivatives

Role of galacturonic acid in acrylamide formation: Insights from structural analysis

Acrylamide (AA) is a neoformed compound in heated foods, mainly produced between asparagine (Asn) and glucose (Glc) during the Maillard reaction. Galacturonic acid (GalA), the major component of pectin, exhibits high activity in AA formation. This study investigated the pathway for AA formation between GalA and Asn. Three possible pathways were proposed: 1) The carbonyl group of GalA directly interacts with Asn to produce AA; 2) GalA undergoes an oxidative cleavage reaction to release α-dicarbonyl compounds, which subsequently leads to AA production; 3) 5-formyl-2-furancarboxylic acid, the thermal degradation product of GalA, reacts with Asn to generate AA. Structural analysis revealed that the COOH group in GalA accelerated intramolecular protonation and electron transfer processes, thereby increasing the formation of AA precursors such as decarboxylated Schiff base and α-dicarbonyl compounds, promoting AA formation. This study provides a theoretical basis and new insights into the formation and control of AA.

Rapid preparation of the Amadori rearrangement product of glutamic acid - xylose through intermittent microwave heating and its browning formation potential in microwave thermal processing

Directional and rapid formation of the Amadori rearrangement product (ARP) from the glutamic acid and xylose was achieved through intermittent microwave heating. The yield of ARP reached 58.09 % by subjecting the system to intermittent microwave heating at a power density of 10 W/g for 14 min. Dehydration rate and microwave effects were found to be key factors to optimize the conditions for directional and rapid preparation of the ARP. Through a comprehensive analysis of the ARP degradation and further browning under both conductive and microwave thermal processing, it was observed that microwave processing significantly accelerated the browning degree of systems, leading to a tenfold reduction in the heating time required for browning. This research presented a promising avenue for the development of novel and expedited methods for the production of ARP and highlighted the potential of ARP in enhancing color quality in fast-cooking applications utilizing microwave.

Investigating Photo-Degradation as a Potential Pheromone Production Pathway in Spotted Lanternfly, Lycorma delicatula

Since its discovery in North America in 2014, the spotted lanternfly (SLF), Lycorma delicatula, has become an economic, ecological, and nuisance pest there. Developing early detection and monitoring tools is critical to their mitigation and control. Previous research found evidence that SLF may use pheromones to help locate each other for aggregation or mating. Pheromone production necessitates specific conditions by the insects, and these must be investigated and described. A chemical process called photo-degradation has been described as a final step in the production of pheromones in several diurnal insect species, in which cuticular hydrocarbons were broken down by sunlight into volatile pheromone components. In this study, photo-degradation was investigated as a possible pheromone production pathway for SLF. Extracts from SLF mixed-sex third and fourth nymphs and male or female adults were either exposed to simulated sunlight to produce a photo-degradative reaction (photo-degraded), or not exposed to light (crude), while volatiles were collected. Behavioral bioassays tested for attraction to volatiles from photo-degraded and crude samples and their residues. In third instars, only the volatile samples from photo-degraded mixed-sex extracts were attractive. Fourth instar males were attracted to both crude and photo-degraded residues, and volatiles of photo-degraded mixed-sex extracts. Fourth instar females were attracted to volatiles of crude and photo-degraded mixed-sex extracts, but not to residues. In adults, only males were attracted to body volatiles from crude and photo-degraded extracts of either sex. Examination of all volatile samples using gas chromatography coupled with mass spectrometry (GC-MS) revealed that most of the identified compounds in photo-degraded extracts were also present in crude extracts. However, the abundance of these compounds in photo-degraded samples were 10 to 250 times more than their abundance in the crude counterparts. Results from behavioral bioassays indicate that photo-degradation probably does not generate a long-range pheromone, but it may be involved in the production of a short-range sex-recognition pheromone in SLF. This study provides additional evidence of pheromonal activity in SLF.

Diet as a Source of Acrolein: Molecular Basis of Aldehyde Biological Activity in Diabetes and Digestive System Diseases

Acrolein, a highly reactive α,β-unsaturated aldehyde, is a compound involved in the pathogenesis of many diseases, including neurodegenerative diseases, cardiovascular and respiratory diseases, diabetes mellitus, and the development of cancers of various origins. In addition to environmental pollution (e.g., from car exhaust fumes) and tobacco smoke, a serious source of acrolein is our daily diet and improper thermal processing of animal and vegetable fats, carbohydrates, and amino acids. Dietary intake is one of the main routes of human exposure to acrolein, which is a major public health concern. This review focuses on the molecular mechanisms of acrolein activity in the context of its involvement in the pathogenesis of diseases related to the digestive system, including diabetes, alcoholic liver disease, and intestinal cancer.

α-Dicarbonyl compounds in food products: Comprehensively understanding their occurrence, analysis, and control

α-Dicarbonyl compounds (α-DCs) are readily produced during the heating and storage of foods, mainly through the Maillard reaction, caramelization, lipid-peroxidation, and enzymatic reaction. They contribute to both the organoleptic properties (i.e., aroma, taste, and color) and deterioration of foods and are potential indicators of food quality. α-DCs are also important precursors to hazardous substances, such as acrylamide, furan, advanced lipoxidation end products, and advanced glycation end products, which are genotoxic, neurotoxic, and linked to several diseases. Recent studies have indicated that dietary α-DCs can elevate plasma α-DC levels and lead to "dicarbonyl stress." To accurately assess their health risks, quantifying α-DCs in food products is crucial. Considering their low volatility, inability to absorb ultraviolet light, and high reactivity, the analysis of α-DCs in complex food systems is a challenge. In this review, we comprehensively cover the development of scientific approaches, from extraction, enrichment, and derivatization, to sophisticated detection techniques, which are necessary for quantifying α-DCs in different foods. Exposure to α-DCs is inevitable because they exist in most foods. Recently, novel strategies for reducing α-DC levels in foods have become a hot research topic. These strategies include the use of new processing technologies, formula modification, and supplementation with α-DC scavengers (e.g., phenolic compounds). For each strategy, it is important to consider the potential mechanisms underlying the formation and removal of process contaminants. Future studies are needed to develop techniques to control α-DC formation during food processing, and standardized approaches are needed to quantify and compare α-DCs in different foods.

Effect of amino acids in the Maillard reaction products generated from the reaction flavors of Tenebrio molitor (mealworm) protein and d-xylose

In this study, Tenebrio molitor (mealworm) protein and reducing sugar were thermally reacted without (MP-RF) or with amino acids (MPA-RFs, A is then replaced with three-letter abbreviation of amino acid used in the reaction), and their Maillard reaction products (MRPs) and sensory characteristics were compared to explore the amino acids that contributed to desirable meat-related odor attributes in MP-RF. The odor characteristics perceived from MP-RF were changed based on the amino acid that was added to MP-RF and then reacted. Noticeably, a 'dried shrimp-like' attribute, which was the most intense in MP-RF, was weakened in all MPA-RFs. The 'meaty' and 'sulfur-like' odor notes were higher in MP-RF reacted with cysteine (MPCys-RF) than those in MP-RF and most MPA-RFs. In addition, 2-methyl-3-furanthiol and 2-furfurylthiol, which are the most important key odorants in a meat flavoring material, were also found only in MPCys-RF. These results show that the meaty flavoring potential of MP-RF was significantly enhanced when reacted with cysteine.

Origin and Fate of Acrolein in Foods

Acrolein is a highly toxic agent that may promote the occurrence and development of various diseases. Acrolein is pervasive in all kinds of foods, and dietary intake is one of the main routes of human exposure to acrolein. Considering that acrolein is substantially eliminated after its formation during food processing and re-exposed in the human body after ingestion and metabolism, the origin and fate of acrolein must be traced in food. Focusing on molecular mechanisms, this review introduces the formation of acrolein in food and summarises both in vitro and in vivo fates of acrolein based on its interactions with small molecules and biomacromolecules. Future investigation of acrolein from different perspectives is also discussed.

N-(1-Deoxy-d-xylulos-1-yl)-glutathione: A Maillard Reaction Intermediate Predominating in Aqueous Glutathione-Xylose Systems by Simultaneous Dehydration-Reaction

The effect of simultaneous dehydration-reaction (SDR) on Amadori rearrangement product (ARP) N-(1-deoxy-d-xylulos-1-yl)-glutathione and its key degradation products, 3-deoxyxylosone (3-DX) and 1-deoxyxylosone (1-DX), were investigated in an aqueous glutathione-xylose (GSH-Xyl) system. The yield of ARP was increased to 67.98% by SDR compared with 8.44% by atmospheric thermal reaction at 80 °C. Reaction kinetics was applied to analyze the mechanism and characteristics of ARP formation and degradation under SDR. ARP formation and degradation rate was highly dependent on temperature, and the latter was more sensitive to temperature. By regulating the reaction conditions of temperature and pH, the ratio of ARP formation rate constant to its degradation rate constant could be controlled to achieve an efficient preparation of ARP from GSH-Xyl Maillard reaction through SDR.

Formation of α-Dicarbonyls from Dairy Related Carbohydrates with and without Nα-Acetyl-l-Lysine during Incubation at 40 and 50 °C

α-Dicarbonyls are reactive intermediates formed during Maillard reactions and carbohydrate degradation. The formation of seven α-dicarbonyls was characterized in solutions containing dairy related carbohydrates (galactose, glucose, lactose, and galacto-oligosaccharides (GOS)) during incubations at 40 and 50 °C with and without Nα-acetyl-l-lysine at pH 6.8 for up to 2 months. The concentrations of α-dicarbonyls in samples of monosaccharides with Nα-acetyl-l-lysine were found to be 3-deoxyglucosone (3-DG) > 3-deoxygalactosone (3-DGal) > glyoxal > glucosone, galactosone > methylglyoxal > diacetyl. The presence of Nα-acetyl-l-lysine resulted in up to 100-fold higher concentrations of C6 α-dicarbonyls but lesser formation of glyoxal in the monosaccharide-containing models compared to what was observed in the absence of Nα-acetyl-l-lysine. Galactose incubated with Nα-acetyl-l-lysine generated the highest concentrations of 3-DGal (up to 130 μM), glyoxal (up to 100 μM), and methylglyoxal (up to 9 μM) compared to the other carbohydrates during incubation. Surprisingly, 3-DG (1500 μM) and 3-DGal (80 μM) were formed at levels of 2 orders of magnitude higher in solutions of GOS in the absence of Nα-acetyl-l-lysine as compared to the other carbohydrates at 40 °C, while GOS generated the lowest levels of glyoxal. GOS are widely used as an ingredient in various types of foods products, and it is therefore of importance to consider the risk of generating high levels of the reactive C6 α-dicarbonyl, 3-DG, in these types of products. This study contributes to the understanding of major α-dicarbonyl formation as affected by the presence of primary amines in GOS-, lactose-, and galactose-containing solutions under moderate heating in liquid foods.

2-Deoxyglucosone: A New C6-α-Dicarbonyl Compound in the Maillard Reaction of d-Fructose with γ-Aminobutyric Acid

In this study, α-dicarbonyl compounds consisting of a backbone with six carbon atoms resulting from the Maillard reaction of d-fructose with γ-aminobutyric acid were determined. The reaction was carried out under mild reaction conditions at 50 °C and water contents between 0 and 90%. A thus far unknown α-dicarbonyl compound was found as the main product in the first 24 h at water contents below 50%. After isolation of its stable quinoxaline derivative, it was possible to identify the compound as 2-deoxy-d- glycero-hexo-3,4-diulose (2-deoxyglucosone). For the first time, the four C₆-α-dicarbonyl compounds, 1-deoxyglucosone, 2-deoxyglucosone, 3-deoxyglucosone, and 4-deoxyglucosone, could be identified in the Maillard reaction of a hexose at the same time. This indicates the formation of a 2,3-eneaminol from the Schiff base of d-fructose and the formation of 2-amino-2-deoxy-3-ketose as an alternative to the Heyns product.

Identification of Cooked Off-Flavor Components and Analysis of Their Formation Mechanisms in Melon Juice during Thermal Processing

Cooked off-flavor components were identified, and their formation mechanisms were studied in heat-treated melon juices. When flavor dilution analysis methods and odor activity values were used to evaluate the cooked off-flavor in heat-treated melon juice, four volatile sulfide compounds (VSCs) were identified as contributors to the cooked off-flavor: dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), dimethyl sulfide (DMS), and 3-(methylthio)propanal (MTP). The cooked off-flavor intensities of heated juices from thick-skinned melons were stronger than those in juices from thin-skinned melons. We conducted a comparative analysis of VSCs before and after heat treatment by adding unlabeled and labeled S-methylmethionine (SMM) and/or methionine (Met) to the original melon juices. DMS and MTP were formed from SMM and Met through nucleophilic substitution and Strecker degradation, respectively. DMDS and DMTS were partly formed through the oxidative degradation of methanethiol produced from Met. Moreover, SMM could accelerate degradation of Met by increasing the amount of dicarbonyl compounds during heat treatment.

Formation of Reactive Intermediates, Color, and Antioxidant Activity in the Maillard Reaction of Maltose in Comparison to d-Glucose

In this study, the Maillard reaction of maltose and d-glucose in the presence of l-alanine was investigated in aqueous solution at 130 °C and pH 5. The reactivity of both carbohydrates was compared in regards of their degradation, browning, and antioxidant activity. In order to identify relevant differences in the reaction pathways, the concentrations of selected intermediates such as 1,2-dicarbonyl compounds, furans, furanones, and pyranones were determined. It was found, that the degradation of maltose predominantly yields 1,2-dicarbonyls that still carry a glucosyl moiety and thus subsequent reactions to HMF, furfural, and 2-acetylfuran are favored due to the elimination of d-glucose, which is an excellent leaving group in aqueous solution. Consequently, higher amounts of these heterocycles are formed from maltose. 3-deoxyglucosone and 3-deoxygalactosone represent the only relevant C₆-1,2-dicarbonyls in maltose incubations and are produced in nearly equimolar amounts during the first 60 min of heating as byproducts of the HMF formation.

Demonstration of physical phenomenas and scavenging activity from d-psicose and methionine maillard reaction products

Maillard reaction has been well understood as a non-enzymatic reaction between reducing sugars and amino acids to generate the Maillard reaction products (MRPs). This study is aimed to demonstrate the browning intensity, color development, spectra measurements, scavenging activity, and the correlation between browning intensity and scavenging activity of the MRPs generated from D-Psicose and Methionine (Psi-Met) at 50℃. The browning intensity of MRPs was investigated based on the absorbance using spectrophotometer at 420 nm, the color development was observed using digital colorimeter to gained L*a*b* value then calculated as browning index, the spectra development was analyzed using spectrophotometer at 190 - 750 nm, and the scavenging activity was determined with ABTS method using spectrophotometer at 734 nm. The browning intensity, color development, and scavenging activity were improved along with the increase in heating process. Based on spectra analysis, MRPs from Psi-Met was initially detected at 21 h and Psi at 24 h of heating treatment, which indicating that Psi-Met have faster and better reaction than Psi during heating process. Positive non-linear and significant correlation between browning intensity and scavenging activity were assigned. This finding may provide beneficial information of D-psicose and MRPs to the next scientific research and to the food industries which applies MRPs in their products.

Browning Potential of C6-α-Dicarbonyl Compounds under Maillard Conditions

In this work, the three major C₆-α-dicarbonyl compounds glucosone (GLUC), 1-deoxyglucosone (1-DG), and 3-deoxyglucosone (3-DG) were synthesized and examined under Maillard conditions (aqueous solutions with the addition of l-alanine at 130 °C and pH 5/8). For the first time, the resulting color formation, antioxidant activity, and generation of short-chained α-dicarbonyls were investigated and compared to incubations of d-glucose and d-fructose. An additive effect on the formation of color, an antagonistic effect on the generation of α-dicarbonyl compounds, and a synergistic effect on the antioxidant activity could be observed for the 1-DG/GLUC combination. Despite their common degradation products, different extinctions could be measured, with 3-DG showing the strongest color formation, followed by GLUC and 1-DG. The analyzed α-dicarbonyl compounds have no direct impact on the formation of color but are precursors for most of the colored compounds. The main difference between the three substances is their ability to form different heterocyclic degradation products, such as pyranones (1-DG), furanones (1-DG), furans (GLUC and 3-DG), and the corresponding N-heterocycles in the presence of amino components. This seems to be the main reason for their varying browning potential and antioxidant activity.

The quality of low lactose milk is affected by the side proteolytic activity of the lactase used in the production process

Lactose intolerance syndrome can be efficiently tackled consuming low lactose products. Lactase is the key tool to manufacture low lactose milk (LLM): its addition during milk processing can be done "in batch", i.e. before thermal treatment, or directly "in pack" after sterilization. In this paper data on sensory properties, Maillard Reaction products (MRPs) and free amino acids formation were obtained on six commercial Italian LLMs over six months storage. They showed that the side proteolytic activity of lactase caused the release of amino acids with a significant higher MRPs and off-flavors formation in four out of five samples produced by adding the enzyme in the pack after thermal treatment. We concluded that the in pack addition of lactase after milk sterilization can have negative sensorial and nutritional consequences mainly related to the enzyme side proteolytic activity especially for prolonged storage time.

D-Galacturonic Acid: A Highly Reactive Compound in Nonenzymatic Browning. 2. Formation of Amino-Specific Degradation Products

Thermal treatment of aqueous solutions of D-galacturonic acid and L-alanine at pH 3, 5, and 8 led to rapid and more intensive nonenzymatic browning reactions compared to similar solutions of other uronic acids and to Maillard reactions of reducing sugars. The hemiacetal ring structures of uronic acids had a high impact on browning behavior and reaction pathways. Besides reductic acid (1,2-dihydroxy-2-cyclopenten-1-one), 4,5-dihydroxy-2-cyclopenten-1-one (DHCP), furan-2-carboxaldehyde, and norfuraneol (4-hydroxy-5-methyl-3-(2H)-furanone) could be detected as typical products of nonenzymatic uronic acid browning reactions. 2-(2-Formyl-1H-pyrrole-1-yl)propanoic acid (FPA) and 1-(1-carboxyethyl)-3-hydroxypyridin-1-ium (HPA) were identified as specific reaction products of uronic acids with amine participation like l-alanine. In contrast, the structurally related D-galacturonic acid methyl ester showed less browning activity and degradation under equal reaction conditions. Pectin-specific degradation products such as 5-formyl-2-furanoic acid and 2-furanoic acid were found but could not be verified for d-galacturonic acid monomers alone.

Studies on the Formation of Maillard and Caramelization Products from Glucosamine Incubated at 37 °C

This experiment compared the in vitro degradation of glucosamine (GlcN), N-acetylglucosamine, and glucose in the presence of NH3 incubated at 37 °C in phosphate buffer from 0.5 to 12 days. The reactions were monitored with UV-vis absorption and fluorescence emission spectroscopies, and the main products of degradation, quinoxaline derivatives of α-dicarbonyl compounds and condensation products, were determined using UHPLC-UV and Orbitrap mass spectrometry. GlcN produced two major dicarbonyl compounds, glucosone and 3-deoxyglucosone, ranging from 709 to 3245 mg/kg GlcN and from 272 to 4535 mg/kg GlcN, respectively. 3,4-Dideoxyglucosone-3-ene, glyoxal, hydroxypyruvaldehyde, methylglyoxal, and diacetyl were also detected in lower amounts compared to glucosone and 3-deoxyglucosone. Several pyrazine condensation products resulting from the reaction between dicarbonyls and GlcN were also identified. This study determined that GlcN is a significantly unstable molecule producing a high level of degradation products at 37 °C.

Model studies on the oxidation of benzoyl methionine in a carbohydrate degradation system

The stability of benzoyl methionine was analyzed during incubation with carbohydrate compounds such as reducing sugars, dicarbonyl compounds, reductones, and Amadori rearrangement products (ARPs). The reaction products were identified and quantified by HPLC-UV and HPLC-MS. In the presence of ARPs, >40% of benzoyl methionine was oxidized to benzoyl methionine sulfoxide after 48 h at 80 °C in acetate-buffered solution (pH 6.0), whereas <10% was oxidized in the presence of mono- and disaccharides. As an important side reaction, peptide bond cleavage through α-amidation was verified. The influence of benzoyl methionine on carbohydrate degradation reactions was assessed through analysis of vicinal dicarbonyl compounds by HPLC-UV. Glyoxal, methylglyoxal, diacetyl, and 3-deoxyglucosone were quantified as the most important derivatives. The thioether group of methionine strongly influenced carbohydrate degradation pathways: Less glyoxal was formed from reducing carbohydrates, showing that benzoyl methionine can act as a radical scavenger. However, more diacetyl was formed from ARPs and reductones, indicating that also radical-dependent pathways could be influenced by benzoyl methionine. The degradation of reducing carbohydrates should thus be an important contributor to protein oxidation in food items with low fat content.

Antioxidant capacity of 1-deoxy-D-erythro-hexo-2,3-diulose and D-arabino-hexo-2-ulose

The antioxidant capacity of two 1,2-dicarbonyl compounds, 1-deoxy-d-erythro-hexo-2,3-diulose (1-deoxyglucosone) and d-arabino-hexo-2-ulose (d-glucosone), was investigated. Both compounds are key intermediates of the Maillard reaction, and both possess a reductone-like structure. The reductive potential of the reductones was measured with the trolox equivalent antioxidant capacity (TEAC) assay and the Folin-Ciocalteu reagent (FCR) assay. Their antioxidant capacity set them apart from their precursors and other typical Maillard reaction products. Using electron paramagnetic resonance (EPR) spectroscopy, the special radical scavenging behavior of 1-deoxyglucosone and d-glucosone was measured. Both exhibited a slow, but constant, scavenging ability over the course of several hours, even days. It was postulated that this characteristic behavior is caused by the isomeric composition and the transformation to the particular antioxidant form. Reaction mixtures of 1-deoxyglucosone showed a correlation between the decrease of antioxidant properties and the decomposition of 1-deoxyglucosone.

Fragmentation pathways during Maillard-induced carbohydrate degradation

The Maillard reaction network with focus on the chemistry of dicarbonyl structures causes considerable interest of research groups in food chemistry and medical science, respectively. Dicarbonyl compounds are well established as the central intermediates in the nonenzymatic browning reaction and have been verified to be responsible for advanced glycation endproduct (AGE) formation. A multitude of Maillard dicarbonyls covering the range of the intact carbon backbone down to C3 and C2 fragments were detected in several carbohydrate systems, for example, in glucose, maltose, or ascorbic acid reactions. By definition, dicarbonyls with a C2-C5 carbon backbone must originate by fission of the original carbon skeleton. The present review deals with the five major mechanisms reported in the literature for dicarbonyl decomposition: (i) retro-aldol fragmentation, (ii) hydrolytic α-dicarbonyl cleavage, (iii) oxidative α-dicarbonyl cleavage, (iv) hydrolytic β-dicarbonyl cleavage, and (v) amine-induced β-dicarbonyl cleavage.

Reactivity of thermally treated α-dicarbonyl compounds

The degradation reaction of thermally treated 3-deoxy-d-erythro-hexos-2-ulose and methylglyoxal, both key intermediates in Maillard chemistry, was investigated. Different analytical strategies were accomplished to cover the broad range of formed products and their different chemical behavior. These involved HPLC-DAD and accordingly LC/MS analysis of the quinoxaline derivates, GC/MS analysis of the acetylated quinoxalines, and GC-FID analysis of the decyl ester of acetic acid. As a main degradation product of 3-deoxy-d-erythro-hexos-2-ulose, 5-(hydroxymethyl)furfural could be identified. At alkaline pH values, 3-deoxy-d-erythro-hexos-2-ulose generated various acids but no colored products. In contrast, thermal treatment of methylglyoxal yielded high molecular weight, brownish products. A dimer of methylglyoxal, first precursor for aldol-based polymerization of methylglyoxal, could be clearly identified by GC/MS.

Novel insights into the maillard catalyzed degradation of maltose

Numerous investigations concerning Maillard degradation of carbohydrates clearly depict the important impact of α-dicarbonyl compounds on changes occurring during preparation of food or physiological processes in vivo. To study the formation of these reactive intermediates during degradation of maltose in the presence of lysine, α-dicarbonyl compounds were isolated, identified and quantified after reaction with o-phenylenediamine to form their stable quinoxaline derivatives. Maltosone and 1,4-dideoxyglucosone were synthesized and incubated independently with lysine to investigate follow-up products and to gain further insights into the complex degradation mechanisms. Glyoxylic acid as a dicarbonyl structure and 5,6-dihydroxy-2,3-dioxohexanal as a 1,2,3-tricarbonyl compound were established as novel Maillard degradation products of maltose. Conducted experiments unequivocally demonstrated that inter- and intramolecular redox reactions are of major importance during degradation of disaccharides. 1,4-Dideoxyglucosone, 1-lysino-1,4-dideoxyglucosone, 5,6-dihydroxy-2,3-dioxohexanal, 3,4-dideoxypentosone and glyoxylic acid were found to be the central intermediates involved in the redox chemistry. With the present study we deliver a comprehensive overview on the mechanisms behind α-dicarbonyl compounds evolving from Maillard degradation of maltose.

3-Deoxygalactosone, a new glucose degradation product in peritoneal dialysis fluids: identification, quantification by HPLC/DAD/MSMS and its pathway of formation

Heat sterilization of peritoneal dialysis (PD) fluids leads to the formation of glucose degradation products (GDPs), which considerably impair long-term application of PD. Knowledge of the exact composition of GDPs present in a PD fluid is important to improve the biocompatibility of dialysis solutions. The present study conducted a targeted screening for novel GDPs with α-dicarbonyl structure in PD fluids. Thus, 3-deoxygalactosone (3-DGal) was identified for the first time in PD fluids. Quantification of 3-DGal was achieved by high-performance liquid chromatography (HPLC)/DAD/MSMS after derivatization with o-phenylendiamine to yield the quinoxaline derivative. Baseline separation of all α-dicarbonyl GDPs, particularly of the diastereomers 3-deoxyglucosone (3-DG) and 3-DGal, required the application of a polar, phenyl-based RP column for HPLC and additional pH-gradient elution. Concentrations of 3-DGal ranged between 55.8 and 136.9 μM in single-chamber PD fluids, and between 2.5 and 12.4 μM in double-chamber PD fluids. In solutions containing glucose, 3-DGal is formed from 3-DG via the intermediate 3,4-dideoxyglucosone-3-ene (3,4-DGE). Further studies are now required to determine the (patho-)physiological properties of 3-DGal.