Effects of Catechins on Nε-(Carboxymethyl)lysine and Nε-(Carboxyethyl)lysine Formation in Green Tea and Model Systems

Influence of hydroxyl substitution on the inhibition of flavonoids in advanced glycation end-products formation in glucose-lysine-arginine Maillard reaction models

Advanced glycation end products (AGEs) generated from the Maillard reaction (MR) during food processing in the human physiological environment, have been proven to be significantly associated with various chronic metabolic diseases. In this study, 18 flavonoids were investigated to study their effects on AGEs formation during MR within a glucose-lysine-arginine model system. Five AGEs- Nε-carboxymethyl-lysine (CML), Nε-carboxyethyl-lysine (CEL), pyrraline, pentosidine, and argpyrimidine-were determined by high-performance liquid chromatography-mass spectrometry, with inhibitory rates ranging between 0 % and 71.35 %. Isorhamnetin and naringenin exhibited the strongest inhibitory effect on the formation of CML and CEL, respectively, whereas myricetin exhibited the strongest inhibitory effect on pyrraline, pentosidine, and argpyrimidine formation. In addition, each flavonoid was reacted with glyoxal (GO) and methylglyoxal (MGO) to investigate their trapping activities and adducts. The results showed that the 18 flavonoids could effectively clear GO and MGO, with clearance rates of 1.03 %-71.42 % and 0.93 %-69.37 % for GO and MGO, respectively. Six flavonoids-chrysin, naringenin, apigenin, luteolin, diosmetin, and kaempferol-could form adduct products with mono-/di-MGO, with flavonoid to mono-/di-MGO adduct ratios of approximately 6:1, 2:1, 8:1, 23:1, 10:1, and 3:1, respectively. The number and site of phenolic hydroxyl groups, as well as methoxy substitution on the B-ring in flavonoids, had little effect, but phenolic hydroxyl groups at the C-3 position in the C-ring impeded adduct formation. The flavonoids lowered the degradation of glucose itself, and decreased ammonia-induced degradation and Amadori rearrangement product oxidation due to their antioxidant activities, and they trapped the reactive 1,2-di‑carbonyl species via nucleophilic addition reaction to form AGEs.

Citral: A potent inhibitor of advanced glycation end products

Advanced glycation end products (AGEs), which are produced during food processing, pose health risks to humans. This study found that citral (Cit) effectively inhibited the formation of both fluorescent and non-fluorescent AGEs in the bovine serum albumin (BSA)-glucose (Glc) system. Cit achieved an average inhibition rate of over 80 % for fluorescent AGEs and reduced the levels of N-ε-carboxymethyllysine (CML) and N-ε-carboxyethyllysine (CEL) by up to 45.85 % and 59.32 %, respectively. The comprehensive characterizations and high-resolution mass spectrometry analysis demonstrated that the carbonyl group and CC group present on Cit could compete with Glc for the amino groups on BSA, thereby reducing the formation of AGEs. Additionally, the cytotoxicity assay demonstrated that the BSA-Cit adducts were non-toxic. This research indicated that Cit was a potent and safe inhibitor of AGEs.

Inhibition of Nε-(carboxyethyl)lysine and Nε-(carboxymethyl)lysine formation in beef, chicken, and fish meat: A comparative study of oven frying and air frying with a marinade-containing Micromeria fruticosa

The objective of this study was to assess the impact of marinating beef, chicken, and fish with Micromeria fruticosa (M. fruticosa) on the inhibition of Nε-(carboxyethyl)lysine (CEL) and Nε-(carboxymethyl)lysine (CML). Furthermore, our objective was to examine how different cooking techniques, temperatures, and durations affect the creation of CEL and CML in these meat products. The study began with the characterization of M. fruticosa. Subsequently, meat samples were marinated using an M. fruticosa-containing marinade and stored at 4 ± 1°C for 24 h. Following storage, the meats underwent cooking in an oven at 200°C for 12 min and in an air fryer at 250°C for 8 min. Subsequently, pH, color, thiobarbituric acid reactive substances (TBARS), as well as CEL and CML analyses were conducted. M. fruticosa had high levels of biological activity and bioactive content. Moreover, increasing the M. fruticosa ratio in the marinade demonstrated a reduction in TBARS, CML, and CEL formation. This study concludes that M. fruticosa can be effectively used as a marinade component for meat, inhibiting the formation of CEL and CML. In conclusion, this research underscores the significant potential of M. fruticosa in reducing the synthesis of advanced glycation end products (AGEs) during meat processing. These results not only enhance our comprehension of the complex relationship between plant extracts and meat quality but also present encouraging prospects for fostering healthier and safer cooking methods.

Inhibitory effect of homemade hawthorn vinegar-based marinade on Nε-(carboxymethyl)lysine and Nε-(carboxyethyl)lysine formation in beef tenderloins

In this study, the inhibitory effects of homemade hawthorn vinegar-based marinade on the formation of Nε-(carboxymethyl) lysine (CML) and Nε-(carboxyethyl) lysine (CEL) during the cooking of beef tenderloins investigated. Additionally, the goal was to determine the bioactive compounds present in hawthorn vinegar that could contribute to these effects, both quantitatively and qualitatively. For this purpose, hawthorn vinegar was first produced from hawthorn fruit and characterized. Then, beef tenderloins were marinated at two different concentrations (25% and 50%) and three different marination times (2, 6 and 24 h) and cooked in a airfryer at 200 °C for 12 min. After the cooking process, analyses were conducted for CML, CEL, thiobarbituric acid reactive substances (TBARS), sensory and color. Hawthorn vinegar was found to have high phytochemical and bioactivity properties. It was found that hawthorn vinegar significantly altered the color properties (L*, a*, and b*) of raw beef tenderloin samples (P < 0.05). The marinating process did not adversely affect the sensory properties of the beef tenderloin, other than odour, and even improved its texture and appearance. Increasing the marination concentration and time significantly inhibited CML and CEL formation (P < 0.05), marinating the meat for 24 h reduced CML formation from 13.75 μg/g to 2.5 μg/g, while CEL formation decreased from 17.58 μg/g to 16.63 μg/g. Although CEL was inhibited at low levels during marination, it remained stable. In conclusion, this study showed that hawthorn vinegar contains bioactive compounds that significantly inhibit the formation of CML and stabilize the formation of CEL.

Effect of marinating with green tea extract on the safety and sensory profiles of oven-baked oyster

Baked oyster is a popular seafood dish around the world. The present study investigated the effect of various concentrations of a green-tea extract (GTE) marinade on the safety and sensory profiles of oysters baked for different durations. The results showed 10 g/L of GTE and 10-min baking time was the optimal combination, as supported by significantly attenuated lipid oxidation (35.29 %) and Nε-(carboxyethyl)lysine (CEL) content (48.51 %) without appreciable negative impact on the sensory or nutritional quality of the oysters. However, high concentrations of the marinade or prolonged baking promoted protein oxidation and Nε-(carboxymethyl)lysine (CML) formation likely through the pro-oxidative action of the GTE phytochemicals. Correlation analysis further revealed the main factors that affected CML, CEL, and fluorescent AGEs generation, respectively. These findings provide theoretical support for the protective effect and mechanism of GTE against quality deterioration of baked oysters and would help broaden the application of GTE in the food industry.

Research progress on generation, detection and inhibition of multiple hazards - acrylamide, 5-hydroxymethylfurfural, advanced glycation end products, methylimidazole - in baked goods

While baking produces attractive flavors for foods, it also generates various endogenous by-products, including acrylamide (AA), 5-hydroxymethylfurfural (5-HMF), advanced glycation end products (AGEs) and methylimidazole (MI). This review briefly presents the recent studies on the above hazards, and research progress on the formation and control of the above substances in detail. There have been more detailed studies on a single category of hazards. However, few studies and reports have considered the integrated prevention and control of multiple hazards, which is related to the difficulty of analyzing the reaction mechanisms of multiple hazards at multiple scales and under multiple phases in complex food matrices. In this regard, the sample pretreatment methods are a crucial step in achieving simultaneous detection. The coordinated implementation of various methods, including reducing precursor levels, modifying baking conditions and equipment, and incorporating exogenous additives, is necessary to achieve a synchronized reduction in multiple hazardous substances.

Inhibitory effect of Paliurus spina-christi Mill., Celtis tournefortii L. and Nigella sativa L. on Nε-(Carboxymethyl) lysine in meatballs

This study was conducted to examine the effect of cooking at different temperatures on the formation of Nε-(carboxymethyl) lysine (CML) after adding Paliurus spina-christi Mill. (PSC), Celtis tournefortii L. (CT) fruits, and Nigella Sativa L. (NS) seeds to the meatballs. Phytochemical and bioactivity properties were determined before adding PSC, CT fruits, and NS seeds to the meatballs. Then, PSC, CT fruits, and NS seeds were added to the meatballs at a rate of 2% and stored at 4 ± 1 °C for 16 days. CML, TBARS, pH, and aw analyses were performed on the meatballs. The highest phytochemical and bioactivity levels were detected in PSC fruit. The aw values detected in the meatball groups were found to be between 0.931 and 0.951 on the 0th day and between 0.963 and 0.985 on the 16th day, and the pH values ranged from 5.66 to 6.06 on the 0th day and from 6.10 to 6.74 on the 16th day. TBARS values of the meatballs were found to be between 1.17 and 1.98 on day 0 and 1.70-3.34 mg MDA/kg on day 16. CML levels in the meatballs were determined to be between 11.15 and 13.45 on day 0 and between 13.43 and 18.17 μg/g on day 16. The highest a* value was found in the meatballs with added CT fruit. It was determined that NS seeds had a negative effect on the a* value of the meatballs. In conclusion, adding PSC, CT fruits, and NS seeds can imbue meatballs with functional properties, thereby creating a more health-beneficial product for humans.

Isotope dilution-HPLC-MS/MS to investigate the production patterns and possible pathways of free and protein-bound AGEs and 4-MI in cookies

A qualitative and quantitative method for detecting free and protein-bound advanced glycation end products (AGEs) and 4-methylimidazole (4-MI) was established using isotope dilution-HPLC-MS/MS, and successfully applied in cookies and model systems. The effects of different temperatures (160-220 °C) on the formation of free and protein-bound AGEs and 4-MI in cookies were discussed, and the possible model systems (Maillard reaction pathway 1 using wheat gluten protein + glucose + sucrose; direct addition pathway 1 using wheat gluten protein + CML/CEL/4-MI) of protein-bound AGEs and 4-MI were verified. The results showed that the contents of protein-bound CML, CEL, and 4-MI were higher than free content with a tendency of increasing first and subsequently decreasing with temperature, reaching a maximum at 200 °C in cookies. In the model systems, the levels of protein-bound CML, CEL, and 4-MI are higher than those of free CML, CEL, and 4-MI. The protein-bound CML, CEL, and 4-MI accounted for 90.73, 87.64, and 97.56% of the total amount in the model system 1, while accounting for 68.19, 59.00, and 50.96% in the model system 2, respectively. In comparison, protein-bound CML, CEL, and 4-MI could be easily generated directly by Maillard reaction.

Inhibitory Effects of Some Hydrocolloids on the Formation of Advanced Glycation End Products and Heterocyclic Amines in Chemical Models and Grilled Beef Patties

Effectively inhibiting the formation of heterocyclic amines (HAs) and advanced glycation end products (AGEs) is crucial to human health. In the present study, chemical model systems were used to evaluate the inhibitory effects of seven hydrocolloids on HA and AGE formation. The results showed that hydrocolloids effectively inhibited the formation of two major AGEs. However, their inhibitory action against HA formation showed unexpected results, wherein alginic acid, carrageenan and konjac glucomannan promoted the formation of 2-Amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP), harmane, norharmane and 2-amino-3,8-dimethyl-imidazo [4,5-f]-quinoline (MeIQx). Only chitosan and pectin showed significant inhibitory effects on HAs, reducing HA levels by 34.5-56.3% and 30.1-56.6%, respectively. In grilled beef patties, the addition of 1.5% chitosan and pectin significantly decreased AGE and HA content by 53.8-67.0% and 46.9-68.1%, respectively. Moreover, it had a limited impact on quality and sensory properties. Further mechanism studies conducted in model systems revealed that chitosan and pectin decreased the formation of key intermediates of AGEs and HAs. These findings suggest that chitosan and pectin are powerful inhibitors against AGE and HA formation with minimal impact on food quality. Therefore, their application in meat preparation and processing could effectively decrease human dietary exposure to HAs and AGEs.

The Influence of Deep Eutectic Solvents Extract from Ginger on the Formation of Heterocyclic Amines and Advanced Glycation End Products in Roast Beef Patties

Heterocyclic amines (HAs) and advanced glycation end products (AGEs) are important harmful products formed simultaneously during the thermal processing of food. In order to develop a green, efficient method that can be used to control the production of two harmful products simultaneously in food processing. In the present study, deep eutectic solvents (DESs) were used to extract ginger, and this method produced significantly higher levels of total phenolic and flavonoid content as well as an antioxidant activity than ginger extracted using conventional solvents. Herein, we further investigated the inhibitory effects of DES extracts from ginger on the generation of HAs and AGEs in roast beef patties. All the nine DES extracts reduced the formation of HAs and AGEs, and the application of choline chloride–lactic-acid-based DES extract caused a signification reduction of 44.33%, 29.38%, 50.95%, 78.61%, 21.94%, and 17.52% of the PhIP, MeIQx, MeIQ, 4,8-DiMeIQx, Harmane, and Norhamane content, and those for Nε-(carboxymethyl)lysine (CML) and Nε-(carboxyethyl)lysine (CEL) were 49.08% and 58.50%, respectively. Furthermore, the proximate and texture profile changes of beef patties as well as the precursors (creatine, creatinine, and glucose) of HAs and AGEs were evaluated to determine the mechanism of ginger DES extracts on the formation of HAs and AGEs and the physical/chemical changes of ginger DES extracts on beef patties. This study develops a new method for reducing the amount of HAs and AGEs in meat, which will help food manufacturers produce healthier meat products.

A novel formation pathway of Nε-(carboxyethyl)lysine from lactic acid during high temperature exposure in wheat sourdough bread and chemical model

N^ε-(carboxymethyl)lysine (CML) and N^ε-(carboxyethyl)lysine (CEL) have been the most extensively studied advanced glycation end-products (AGEs) in foods. Their formation mechanism, especially the latter, has not been clearly delineated in fermented food. In this work, the relative contents of CEL and CML were evaluated in a sourdough-bread and a silica solid chemical model. Lactic acid (LA) content in the sourdough increased with fermentation time that was accompanied by an increase in CEL, but not CML content in the bread. The role of LA as a precursor for CEL was supported by a positive significant correlation between LA and CEL contents, and further analysis using isotope-labeled LA (LA-¹³C₃) revealed that the three carbon atoms of LA were incorporated into CEL. These findings for the first time indicate LA may function as a precursor to promote CEL formation in sourdough bread that merits further investigation.

Effects of Various Processing Methods on the Metabolic Profile and Antioxidant Activity of Dendrobium catenatum Lindley Leaves

The metabolite profiles and antioxidant activity of Dendrobium catenatum Lindley leaf, a new functional ingredient for food product development, were evaluated in samples that had been prepared using various methods, including freeze-drying, hot-air drying, rolling before drying, steaming before drying, steaming and rolling before drying, and drying at 100, 80, and 60 °C. The concentrations of polysaccharides and flavonoids, as well as the antioxidant capacity of each sample, were determined. Furthermore, two nucleosides, four amino acids, one monoaromatic compound, and eight flavonoids were identified in dried leaves using high-performance liquid chromatography-diode array detector-electrospray ionization-multistage mass spectrometry (HPLC-DAD-ESI-MSn) and ultraviolet (UV) spectral analyses. The content of polar compounds such as cytidylic acid, arginine, tyrosine, and hydroxybenzoic acid hexose increased dramatically during hot-air-drying and rolling-before-drying treatments, while flavonol C-glycosides remained stable throughout the various treatments and drying temperatures. Rolling before drying at 100 °C was identified as the most suitable process when manufacturing tea products from D. catenatum leaves. This process resulted in a high-antioxidant-activity and visually appealing tea. This report details a potential strategy that should be applied in the manufacturing processes of high-quality products from D. catenatum leaves.

Air frying combined with grape seed extract inhibits Nε-carboxymethyllysine and Nε-carboxyethyllysine by controlling oxidation and glycosylation

Advanced glycation end products (AGE), compounds formed in meat at the advanced stage of Maillard reaction, are easily exposed to thermal processing. Improving cooking condition and adding antioxidants are 2 common ways for AGE reduction. The present work compared the inhibition of grape seed extract (GSE) on levels of free and protein-bound N^ε-carboxymethyllysine (CML) and N^ε-carboxyethyllysine (CEL) in chicken breast under deep-frying and air-frying conditions. Efficiency of 5 concentrations of GSE (0.0, 0.2, 0.5, 0.8, and 1.0 g/kg) in retarding oxidation, glyoxal (GO), methylglyoxal (MGO), lysine (Lys), Maillard reaction degree (A₂₉₄, A₄₂₀), and Shiff's base were tested. Results showed that 0.5 g/kg GSE before heating significantly (P < 0.05) reduced AGE in fried breast chicken, whereas excessive supplementation of GSE (0.8 and 1 g/kg) was reverse. Air frying was found significantly (P < 0.05) better than deep frying to reduce the precursor substances (GO, MGO, and Lys) of AGE. In conclusion, GSE-derived polyphenols exhibited different inhibitory effects on oxidation and glycosylation at different concentrations. We found that 0.5 g/kg of GSE combined with air frying was the best recommendation for inhibiting CML and CEL.

Green Tea Extract Decreases Arg-Derived Advanced Glycation Endproducts but Not Lys-Derived AGEs in UHT Milk during 1-Year Storage

Epigallocatechin gallate (EGCG)-enriched green tea extract (GTE) was added to lactose-reduced UHT-treated milk to evaluate its role in perturbing the Maillard reaction and the formation of advanced glycation endproducts (AGEs) during 1-year storage. The UHT processing caused epimerization of EGCG into gallocatechin gallate (GCG). For milk samples with added 0.1% w/v GTE, a EGCG/GCG loss of 26% was found soon after the UHT treatment and the loss increased to 64% after the 1-year of storage. LC-MS/MS analysis revealed the presence of various EGCG/GCG-α-dicarbonyl adducts and EGCG/GCG-hydroxymethylfurfural adducts in milk samples, while EGCG/GCG-amino acid adducts were not detected. Although EGCG/GCG trapped α-dicarbonyl compounds including glyoxal, methylglyoxal, 3-deoxyglucosone/3-deoxygalactosone, and diacetyl, it did not lower their net steady-state concentrations, except of 3-deoxyglucosone. The addition of GTE reduced the formation of Arg-derived AGEs by 2- to 3-fold, but surprisingly enhanced the accumulation of furosine and lysine-derived AGEs [Nε-(carboxymethyl)lysine and Nε-(carboxyethyl)lysine)] by 2-4-fold depending on the concentration of the added GTE and storage time. The present study shows that trapping of α-dicarbonyl compounds by EGCG may not be the major pathway for inhibiting the formation of AGEs in milk.

Lipids Promote Glycated Phospholipid Formation by Inducing Hydroxyl Radicals in a Maillard Reaction Model System

Food-derived glycated phospholipids is potentially hazardous to human health. However, there are few studies on the effects of lipids on the formation of glycated phospholipids. In this work, two model systems were established: (1) a model system including 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (PE), glucose, and Fenton reagent and (2) a model system including PE, glucose, and five kind of vegetable oils. The contents of carboxymethyl-PE, carboxyethyl-PE, Amadori-PE, hydroxyl radical (OH•), glyoxal, and methylglyoxal were determined with high-performance liquid chromatography mass spectrometry. The results of the first model system showed that OH• oxidized glucose to produce glyoxal and methylglyoxal, which then reacted with PE to form carboxymethyl-PE and carboxyethyl-PE. OH• also oxidized Amadori-PE to form carboxymethyl-PE. The results of the second model system showed that vegetable oils with higher number of moles of carbon-carbon unsaturated double bond in vegetable oil per kilogram could produce more OH•, which promote the formation of carboxymethyl-PE and carboxyethyl-PE by oxidizing glucose and oil. We elucidated the effects of oils on the formation of glycated phospholipids in terms of OH• and intermediates. This work will contribute to better understanding the formation mechanism of glycated phospholipids with oil.