Recent advances in molecularly imprinted polymers (MIPs) for visual recognition and inhibition of α-dicarbonyl compound-mediated Maillard reaction products

α-Dicarbonyl compounds (α-DCs) are important intermediates and precursors of harmful Maillard reaction products (e.g., acrylamide and late glycosylation end-products), and they exist widely in thermoprocessed sugar- or fat-rich foods. α-DCs and their end-products are prone to accumulation in the human body and lead to the development of various chronic diseases. Therefore, detection of α-DCs and their associated hazards in food samples is crucial. This paper reviews the preparation of molecularly imprinted polymers (MIPs) enabling visual intelligent responses and the strategies for recognition and capture of α-DCs and their associated hazards, and provides a comprehensive summary of the development of visual MIPs, including integration strategies and applications with real food samples. The visual signal responses as well as the mechanisms for hazard recognition and capture are highlighted. Current challenges and prospects for visual MIPs with advanced applications in food, agricultural and environmental samples are also discussed. This review will open new horizons regarding visual MIPs for recognition and inhibition of hazards in food safety.

Advances of nanoparticle derived from food in the control of α-dicarbonyl compounds-A review

α-Dicarbonyl compounds (α-DCs) are predominantly generated through the thermal processing of carbohydrate and protein-rich food. They are pivotal precursors to hazard formation, such as advanced glycation end products (AGEs), acrylamide, and furan. Their accumulation within the body will be genotoxicity and neurotoxicity. Recently, significant advancements have been made in nanotechnology, leading to the widespread utilization of nanomaterials as functional components in addressing the detrimental impact of α-DCs. This review focuses on the control of α-DCs through the utilization of nanoparticle-based functional factors, which were prepared by using edible components as resources. Four emerging nanoparticles are introduced including phenolic compounds-derived nanoparticle, plant-derived nanoparticle, active peptides-derived nanoparticle, and functional minerals-derived nanoparticle. The general control mechanisms as well as the recent evidence pertaining to the aforementioned aspects were also discussed, hoping to valuable helpful references for the development of innovative α-DCs scavengers and identifying the further scope of research.

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.

Molecularly imprinted thermosensitive probe based on fluorescent advanced glycation end products to detect α-dicarbonyl compounds and inhibit pyrraline formation

A thermal-sensitive molecularly imprinted optosensing probe based on fluorescent advanced glycation end products (AGEs) was prepared by one-pot hydrothermal synthesis. Carbon dots (CDs) derived from fluorescent AGEs were used as the luminous centers, while molecularly imprinted polymers (MIPs) were wrapped outside of the CDs to form specific target recognition sites to highly selectively adsorb the intermediate product of AGEs of 3-deoxyglucosone (3-DG). Thermosensitive N-isopropylacrylamide (NIPAM) was combined with acrylamide (AM) as co-functional monomers, and ethylene glycol dimethacrylate (EGDMA) was chosen as a cross-linker for targeting identification and detection of 3-DG. Under optimal conditions, the fluorescence of MIPs could be gradually quenched with the adsorption of 3-DG on the surface of MIPs in the linear range of 1-160 μg/L, and the detection limit was 0.31 μg/L. The spiked recoveries of MIPs ranged from 82.97 to 109.94% in two milk samples, and the relative standard deviations were all less than 1.8%. In addition, the inhibition rate for non-fluorescent AGEs of pyrraline (PRL) was 23% by adsorbing 3-DG in the simulated milk system of casein and D-glucose, indicating that temperature-responsive MIPs not only could detect the dicarbonyl compound 3-DG quickly and sensitively, but also had an excellent inhibitory effect on AGEs.

Investigation on the contents of heat-induced hazards in commercial nuts

The purpose was to investigate the contents of heat-induced hazards by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in 44 commercial nuts. Results showed that content ranges of Acrylamide (AA), 5-hydroxymethylfurfural (5-HMF), N^ε-carboxymethyl-lysine (CML), N^ε-carboxyethyl-lysine (CEL), 3-Deoxyglucosone (3-DG), Glyoxal (GO), and Methylglyoxal (MGO) were ND-123.57 µg/kg, 0.57-213.42 mg/kg, 3.18-18.67 mg/kg, 3.98-57.85 mg/kg, 1.5-133.86 mg/kg, 0.45-1.59 mg/kg and 0.29-13.84 mg/kg, respectively. Sunflower seeds contained more heat-induced hazards followed by pistachios, cashews, almonds, walnuts and hazelnuts. The content of 5-HMF was positively correlated with the content of 3-DG. CML exhibited positive correlation with content of GO while no correlation between CEL and MGO. Higher levels of 3-DG and 5-HMF were observed in nuts produced with sugar and honey. Deep processing had a stronger promoting effect on CML and CEL formation. These data could provide a crucial guide for consumers to select nut products which might reduce heat-induced hazards intake.

Effects of sprouting and fermentation on the formation of Maillard reaction products in different cereals heated as wholemeal

The concentration and composition of reducing sugars and free amino acids as Maillard reaction (MR) precursors change with grain sprouting. The formation of early and advanced glycation products, and α-dicarbonyl compounds as intermediates were monitored during heating native and sprouted wholemeals, as well as during heating of yeast and sourdough fermented native and sprouted wholemeals. Sprouting increased the concentration of all MR products because of an increase in reducing sugar concentrations. Although reducing sugars were lowered due to their consumption by yeasts, fermentation did not lower the furosine concentration. Sourdough fermentation unexpectedly increased furosine because the low pH caused glucose release from polysaccharides. Glyoxal, methylglyoxal and diacetyl were found to be formed as metabolites during yeast and sourdough fermentation. Another factor affecting the MR in sprouted/fermented wholemeals was revealed to be the increased amount of total free amino acids that compete with bound lysine to react with reducing sugars.

Comparison of pyrazines formation in methionine/glucose and corresponding Amadori rearrangement product model

The generation of pyrazines in a binary methionine/glucose (Met/Glc) mixture and corresponding methionine/glucose-derived Amadori rearrangement product (MG-ARP) was studied. Quantitative analyses of pyrazines and methional revealed that MG-ARP generated more methional compared to Met/Glc, whereas lower content and fewer species of pyrazines were observed in the MG-ARP model. Comparing the availability of α-dicarbonyl compounds generated from the Met/Glc model, methylglyoxal (MGO) was a considerably effective α-dicarbonyl compound for the formation of pyrazines during MG-ARP degradation, but glyoxal (GO) produced from MG-ARP did not effectively participate in the corresponding formation of pyrazines due to the asynchrony on the formation of GO and recovered Met. Diacetyl (DA) content was not high enough to form corresponding pyrazines in the MG-ARP model. The insufficient interaction of precursors and rapid drops in pH limited the formation of pyrazines during MG-ARP degradation. Increasing reaction temperature could reduce the negative inhibitory effect by promoting the content of precursors.

Maillard reaction products and amino acid cross-links in liquid infant formula: Effects of UHT treatment and storage

The formation of Maillard reaction products, including Amadori compounds (determined as furosine), advanced glycation end products (AGEs), α-dicarbonyl and furfural compounds, as well as amino acid cross-links (lysinoalanine and lanthionine) was investigated in direct (DI) and indirect (IN) UHT-treated experimental liquid infant formula (IF) during storage at 40 °C. IN-IF had higher concentrations of all investigated compounds compared to DI-IF and low pasteurized IF. IN UHT treatment induced significantly higher concentrations of α-dicarbonyl compounds (glyoxal, methylglyoxal, 3-deoxyglucosone and 3-deoxygalactosone) compared to DI, which facilitated increased formation of AGEs (N-Ɛ-(carboxymethyl)lysine, methylglyoxal- and glyoxal-derived hydroimidazolones) in unstored IFs. During storage for 6 months, concentrations of furosine and AGEs increased while α-dicarbonyl compounds decreased. Principal component analysis indicated that differences between IN-IF and DI-IF disappeared after 2 months of storage. IN-IF had higher concentrations of lysinoalanine and lanthionine and lower concentrations of available lysine and arginine than DI-IF indicating higher loss of protein quality in IN-IF.

Investigations on the formation of Maillard reaction products in sweet cookies made of different cereals

In this study, the content of Maillard reaction products from its initial, intermediate and final stage (5-hydroxymethylfurfural, α-dicarbonyl compounds, furosine, N-ε-carboxymethyllysine and N-ε-carboxyethyllysine) was measured in sweet cookies made of wholegrain flour of eight genotypes of small-grain cereals (bread wheat, durum wheat, soft wheat, hard wheat, triticale, rye, hulless barley and hulless oat) and four corn genotypes (white-, yellow- and red-colored standard seeded corn and blue-colored popping corn). Furthermore, the effect of the initial content of sugars, total proteins, free and total lysine in flour on the formation of Maillard reaction products was investigated using the principle component analysis. 3-deoxyglucosone was the predominant α-dicarbonyl compound in all cereal cookies and the highest content was measured in those made from flour of different colored corn genotypes (on average, 98.35, 151.28 and 172.85 mg/kg after baking for 7, 10 and 13 min, respectively). Heating dough at 180 °C for 7, 10 and 13 min differently affected the content of 5-hydroxymethylfurfural and α-dicarbonyl compounds in the cereal cookies. The 5-hydroxymethylfurfural content gradually increased, while a reduction in 3-deoxyglucosone content was observed in the cookies baked for 13 min except for those made from soft wheat, hulless oat, red- and blue-colored corn. After 7 min of heating, the content of furosine measured in the cereal cookies reached its maximum (from 320.9 mg/kg in yellow-colored corn-based cookies to 585.7 mg/kg in hulless oat-based cookies), while N-ε-carboxymethyllysine and N-ε-carboxyethyllysine showed the opposite trend. The highest content of advanced glycation end products was detected in cookies also made from hulless oat flour rich in proteins (16.80%) and total lysine (10670.3 mg/kg). The interrelationship analysis showed that the initial content of sugars in flour of cereals affected 5-hydroxymethylfurfural and 3-deoxyglucosone formation in the cookies. In addition, a high correlation between protein-bound Maillard reaction products in the cookies and the total proteins and the total lysine content in the flours was found.

Detection of acacia honey adulteration with high fructose corn syrup through determination of targeted α‑Dicarbonyl compound using ion mobility-mass spectrometry coupled with UHPLC-MS/MS

High-value acacia honey is often adulterated with inexpensive high fructose corn syrup (HFCS), due to their similar color and sugar composition. α‑Dicarbonyl compounds formed by Maillard reaction or caramelization during heat treatment or storage, differ between HFCS and honey due to differences in starting materials and processing methods. In this study, we compared α-dicarbonyl compounds in acacia honey and HFCS by Ion Mobility-Mass Spectrometry and multivariate statistical analysis. Through α-dicarbonyl compound derivatization with o-phenylenediamine, we screened a marker with 189.1023 m/z and 139.3 Å² Collision Cross-Section that can distinguish HFCS from acacia honey. Nuclear magnetic resonance spectra identified this marker compound as 3,4-dideoxypentosulose. We then used chromatography-coupled tandem mass spectrometry to quantitate 3,4-dideoxypentosulose in market samples of honey and HFCS and found that 3,4-dideoxypentosulose was negligible (<0.098 mg/kg) in honey, but prevalent in HFCS (≧1.174 mg/kg), indicating 3,4-dideoxypentosulose can serve as an alternative indicator of HFCS adulteration of acacia honey.

Probing glycation potential of dietary sugars in human blood by an integrated in vitro approach

Glycation is referred to as the interaction of protein amino and guanidino groups with reducing sugars and carbonyl products of their degradation. Resulting advanced glycation end-products (AGEs) contribute to pathogenesis of diabetes mellitus and neurodegenerative disorders. Upon their intestinal absorption, dietary sugars and α-dicarbonyl compounds interact with blood proteins yielding AGEs. Although the differences in glycation potential of monosaccharides are well characterized, the underlying mechanisms are poorly understood. To address this question, d-glucose, d-fructose and l-ascorbic acid were incubated with human serum albumin (HSA). The sugars and α-dicarbonyl intermediates of their degradation were analyzed in parallel to protein glycation patterns (exemplified with hydroimidazolone modifications of arginine residues and products of their hydrolysis) by bottom-up proteomics and computational chemistry. Glycation of HSA with sugars revealed 9 glyoxal- and 14 methylglyoxal-derived modification sites. Their dynamics was sugar-specific and depended on concentrations of α-dicarbonyls, their formation kinetics, and presence of stabilizing residues in close proximity to the glycation sites.

Glycation from α-dicarbonyl compounds has different effects on the heat-induced aggregation of bovine serum albumin and β-casein

α-Dicarbonyl compounds are generated in large amounts during heat treatment in food production. This work compared the influence of glycation by α-dicarbonyl on the hydrothermal aggregation of bovine serum albumin (BSA) and of β-casein (β-CN). Glycation by α-dicarbonyl compounds was found to be more efficient than glycation by glucose in reducing the free amino groups, surface hydrophobicity and isoelectric point of BSA, thus greatly inhibited the hydrothermal aggregation of BSA. In addition, glycation by α-dicarbonyl greatly transformed the rigid BSA aggregates into flexible structures, based on analysis by fluorescence spectrum, transmission electron microscope and small-angle X-ray scattering. In contrast, both the aggregation process and aggregates conformation of β-CN were found to be minimally affected by glycation, possibly due to the intrinsic disorder of β-CN. This work highlights the substantial influences of α-dicarbonyl on dietary proteins during heat treatment depending on the protein structural characteristics.

Elevated levels of α-dicarbonyl compounds in the plasma of type II diabetics and their relevance with diabetic nephropathy

The presence of α‑dicarbonyl compounds (α-DCs) in vivo has been associated with the development of complications of diabetes mellitus (DM) and also with other chronic diseases. Therefore, quantitative analysis of α-DCs in body fluids is crucial to understand their roles in the formation of these chronic diseases. We established in this study a practical HPLC-UV method to measure 3‑deoxyglucosone (3-DG), glyoxal (GO), methylglyoxal (MGO), diacetyl (DA), and pentane‑2,3‑dione (PD) in blood plasma using 4‑(2,3‑dimethyl‑6‑quinoxalinyl)‑1,2‑benzenediamine (DQB) as a derivatizing reagent. The derivatizing reaction could be carried out quickly under mild conditions and the HPLC determination is simple, sensitive, and easy to operate. The recoveries of the α-DCs are between 85.26% and 110.20% (intra-day) and 87.25% and 103.18% (inter-day); the RSDs are between 1.28% and 5.69% (intra-day) and 2.26% and 6.34% (inter-day). We found the plasma levels of 3-DG, GO, and MGO in the diabetic patients are all significantly higher than those in healthy subjects. The results also show that the contents of GO and MGO in diabetic nephropathy (DN) patients are both significantly higher than those in simple T2DM patients. Moreover, it is found for the first time that the plasma level of GO might be a potential predictor of DN. The developed method would be useful for the measurements of the plasma α-DCs and the data acquired could be informative in the diagnosis of DM complications.

Levels and formation of α-dicarbonyl compounds in beverages and the preventive effects of flavonoids

ABSTRACT

Methylglyoxal (MGO) and glyoxal (GO), α-dicarbonyl compounds found in the Maillard reaction, progressively and irreversibly modify proteins. Beverages are an exogenous source of α-dicarbonyl compounds and may potentially increase MGO and GO levels in vivo. Using GC-FID method, we detected the MGO and GO contents of 86 beverages in Chinese supermarkets. The highest MGO and GO 587.5 µg/100 mL and 716.7 µg/100 mL respectively found in soyamilk and coffee. Herbal beverages, which contained bioactive components, had lower average levels of MGO (48.1 µg/100 mL) and GO (25.9 µg/100 mL). A box-and-whisker plot was used to display variation of the same group drinks, and comparing distributions between six different groups. It was further discovered that fat, protein and flavonoids, in addition to sweeteners, had notable effects on the formation of MGO and GO in soybean milk. The result of LC/MS indicated that quercetin could prevent the formation of MGO by trapping MGO to form the mono-MGO and di-MGO adducts during soybean milk manufacturing.

GRAPHICAL ABSTRACT

The Role of Oxidative Stress in Diabetic Neuropathy: Generation of Free Radical Species in the Glycation Reaction and Gene Polymorphisms Encoding Antioxidant Enzymes to Genetic Susceptibility to Diabetic Neuropathy in Population of Type I Diabetic Patients

Diabetic neuropathy (DN) represents the main cause of morbidity and mortality among diabetic patients. Clinical data support the conclusion that the severity of DN is related to the frequency and duration of hyperglycemic periods. The presented experimental and clinical evidences propose that changes in cellular function resulting in oxidative stress act as a leading factor in the development and progression of DN. Hyperglycemia- and dyslipidemia-driven oxidative stress is a major contributor, enhanced by advanced glycation end product (AGE) formation and polyol pathway activation. There are several polymorphous pathways that lead to oxidative stress in the peripheral nervous system in chronic hyperglycemia. This article demonstrates the origin of oxidative stress derived from glycation reactions and genetic variations within the antioxidant genes which could be implicated in the pathogenesis of DN. In the diabetic state, unchecked superoxide accumulation and resultant increases in polyol pathway activity, AGEs accumulation, protein kinase C activity, and hexosamine flux trigger a feed-forward system of progressive cellular dysfunction. In nerve, this confluence of metabolic and vascular disturbances leads to impaired neural function and loss of neurotrophic support, and over the long term, can mediate apoptosis of neurons and Schwann cells, the glial cells of the peripheral nervous system. In this article, we consider AGE-mediated reactive oxygen species (ROS) generation as a pathogenesis factor in the development of DN. It is likely that oxidative modification of proteins and other biomolecules might be the consequence of local generation of superoxide on the interaction of the residues of L-lysine (and probably other amino acids) with α-ketoaldehydes. This phenomenon of non-enzymatic superoxide generation might be an element of autocatalytic intensification of pathophysiological action of carbonyl stress. Glyoxal and methylglyoxal formed during metabolic pathway are detoxified by the glyoxalase system with reduced glutathione as co-factor. The concentration of reduced glutathione may be decreased by oxidative stress and by decreased in situ glutathione reductase activity in diabetes mellitus. Genetic variations within the antioxidant genes therefore could be implicated in the pathogenesis of DN. In this work, the supporting data about the association between the -262T > C polymorphism of the catalase (CAT) gene and DN were shown. The -262TT genotype of the CAT gene was significantly associated with higher erythrocyte catalase activity in blood of DN patients compared to the -262CC genotype (17.8 ± 2.7 × 10(4) IU/g Hb vs. 13.5 ± 3.2 × 10(4) IU/g Hb, P = 0.0022). The role of these factors in the development of diabetic complications and the prospective prevention of DN by supplementation in formulations of transglycating imidazole-containing peptide-based antioxidants (non-hydrolyzed carnosine, carcinine, n-acetylcarcinine) scavenging ROS in the glycation reaction, modifying the activity of enzymic and non-enzymic antioxidant defenses that participate in metabolic processes with ability of controlling at transcriptional levels the differential expression of several genes encoding antioxidant enzymes inherent to DN in Type I Diabetic patients, now deserve investigation.