Formation of Hesperetin-Methylglyoxal Adducts in Food and In Vivo, and Their Metabolism In Vivo and Potential Health Impacts.

Polyphenols with a typical meta-phenol structure have been intensively investigated for scavenging of methylglyoxal (MGO) to reduce harmful substances in food. However, less attention has been paid to the formation level of polyphenol-MGO adducts in foods and in vivo and their absorption, metabolism, and health impacts. In this study, hesperitin (HPT) was found to scavenge MGO by forming two adducts, namely, 8-(1-hydroxyacetone)-hesperetin (HPT-mono-MGO) and 6-(1-hydroxyacetone)-8-(1-hydroxyacetone)-hesperetin (HPT-di-MGO). These two adducts were detected (1.6-15.9 mg/kg in total) in cookies incorporated with 0.01%-0.5% HPT. HPT-di-MGO was the main adduct detected in rat plasma after HPT consumption. The adducts were absorbed 8-30 times faster than HPT, and they underwent glucuronidation and sulfation in vivo. HPT-mono-MGO would continue to react with endogenous MGO in vivo to produce HPT-di-MGO, which effectively reduced the cytotoxicity of HPT and HPT-mono-MGO. This study provided data on the safety of employing HPT as a dietary supplement to scavenge MGO in foods.

Esterification of black bean anthocyanins with unsaturated oleic acid, and application characteristics of the product.

Esterification of anthocyanins with saturated fatty acids have been widely investigated, while that with unsaturated fatty acids is little understood. In this study, crude extract (purity âˆ¼ 35 %) of cyanidin-3-O-glucoside (C3G) from black bean seed coat was utilized as reaction substrate, and enzymatically acylated with unsaturated fatty acid (oleic acid). Optimization of various reaction parameters finally resulted in the highest acylation rate of 54.3 %. HPLC-MS/MS and NMR analyses elucidated the structure of cyanidin-3-O-glucoside-oleic acid ester (C3G-OA) to be cyanidin-3-O-(6″-octadecene)-glucoside. Introduction of oleic acid into C3G improved the lipophilicity, antioxidant ability, and antibacterial activity. Further, the color and substance stability analyses showed that the susceptibility of C3G and C3G-OA to different thermal, peroxidative, and illuminant treatments were highly pH dependent, which suggested individual application guidelines. Moreover, C3G-OA showed lower toxicity to normal cell (QSG-7701) and better inhibitory effect on the proliferation of HepG2 cells than C3G, which indicated its potential anti-tumor bioactivity.

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.

Preparation and Characterization of a Novel Natural Quercetin Self-Stabilizing Pickering Emulsion.

In contrast to their well-known physiological properties, phytochemicals, such as flavonoids, have been less frequently examined for their physiochemical properties (e.g., surface activity). A natural quercetin self-stabilizing Pickering emulsion was fabricated and characterized in the present study. The antisolvent precipitation method was used to modify quercetin (in dihydrate form), and the obtained particles were characterized by light microscope, atom force microscope, XRD, and contact angle. The antisolvent treatment was found to reduce the particle size, crystallinity, and surface hydrophobicity of quercetin. We then examined the effects of the antisolvent ratio, particle concentration, and oil fraction on the properties of the quercetin particle-stabilized emulsions. In addition, increasing the antisolvent ratio (1:1~1:10) effectively improved the emulsification performance of the quercetin particles. The emulsion showed good storage stability, and the particle size of the emulsion decreased with the rising particle concentration and increased with the rising oil phase ratio. The findings indicate that natural quercetin treated with antisolvent method has a good ability to stabilize Pickering emulsion, and this emulsion may have good prospective application potential for the development of novel and functional emulsion foods.

Formation and metabolism of 6-(1-acetol)-8-(1-acetol)-rutin in foods and in vivo, and their cytotoxicity.

Methylglyoxal (MGO) is a highly reactive precursor which forms advanced glycation end-products (AGEs) in vivo, which lead to metabolic syndrome and chronic diseases. It is also a precursor of various carcinogens, including acrylamide and methylimidazole, in thermally processed foods. Rutin could efficiently scavenge MGO by the formation of various adducts. However, the metabolism and safety concerns of the derived adducts were paid less attention to. In this study, the optical isomers of di-MGO adducts of rutin, namely 6-(1-acetol)-8-(1-acetol)-rutin, were identified in foods and in vivo. After oral administration of rutin (100 mg/kg BW), these compounds reached the maximum level of 15.80 µg/L in plasma at 15 min, and decreased sharply under the quantitative level in 30 min. They were detected only in trace levels in kidney and fecal samples, while their corresponding oxidized adducts with dione structures presented as the predominant adducts in kidney, heart, and brain tissues, as well as in urine and feces. These results indicated that the unoxidized rutin-MGO adducts formed immediately after rutin ingestion might easily underwent oxidation, and finally deposited in tissues and excreted from the body in the oxidized forms. The formation of 6-(1-acetol)-8-(1-acetol)-rutin significantly mitigated the cytotoxicity of MGO against human gastric epithelial (GES-1), human colon carcinoma (Caco-2), and human umbilical vein endothelial (HUVEC) cells, which indicated that rutin has the potential to be applied as a safe and effective MGO scavenger and detoxifier, and AGEs inhibitor.

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.

Formation and Identification of Six Amino Acid - Acrylamide Adducts and Their Cytotoxicity Toward Gastrointestinal Cell Lines.

Acrylamide (AA) is a food contaminant, and amino acids are suggested to mitigate its toxicity by forming adducts. The emergence of acrylamide adducts may cause underestimation of acrylamide exposure level as well as trigger new safety problems. Based on the acrylamide elimination capability of four amino acids, this study chemically synthesized six amino acid-acrylamide adducts. Their structures were analyzed, followed by content determination in 10 commercially baking foods. The Michael adduct formed by one molecule of γ-aminobutyric acid (GABA) and acrylamide was most abundant in foods among six adducts. Furthermore, it markedly decreased the cytotoxicity of acrylamide in Caco-2 cells and GES-1 cells. This finding suggests that amino acids can be used to reduce acrylamide level in processed foods and mitigate its hazardous effects after intake.

Water-In-Oil Pickering Emulsions Stabilized by Microcrystalline Phytosterols in Oil: Fabrication Mechanism and Application as a Salt Release System.

Recently, Pickering emulsions stabilized by edible particles have attracted significant attention from the scientific community and food industry owing to their surfactant-free character. However, those edible particles are mostly used for stabilizing oil-in-water emulsions, whereas those for water-in-oil emulsions are very limited. In this article, stable water-in-oil Pickering emulsions were prepared through dispersing phytosterol particles in oil phase, and the effects of antisolvent treatment, the type of oil, particle concentration, and water fraction on the stability, type, and morphology of these emulsions were investigated. In addition, the release profile of salt as a model aqueous compound from these emulsions has also been studied. Results showed that due to its higher water content, the antisolvent pretreatment of phytosterol in the ethanol/water system facilitated the dispersion of dried phytosterol particles into oil phase as microcrystals. Water-in-oil Pickering emulsions with droplet sizes of 80-100 µm were fabricated at phytosterol concentrations of 1.5-3% w/v and water fractions of 0.2-0.6. The dissolved phytosterol molecules in oil phase could help in emulsion stabilization through interfacial crystallization during emulsification, evidenced by polar microscopic observations. Moreover, the salt release from phytosterol-stabilized Pickering emulsions showed a temperature-dependent profile which could have potential application in a controlled-release system. The current study provided important information for fabrication of stable water-in-oil emulsion using natural particles.

Identification and cytotoxic evaluation of the novel rutin-methylglyoxal adducts with dione structures in vivo and in foods.

Flavonoids with meta-hydroxyl groups have been proven to react with methylglyoxal (MGO) and form mono- and di-MGO adducts via nucleophilic addition reactions. Rutin, a rutinoside of quercetin with typical meta-phenol structure, is widely distributed in plant-sourced materials. Interestingly, different from the adducts reported between flavonoids and MGO, new rutin-MGO adducts with dione structures on the moiety of MGO were identified and proven to occur in various foods (0.66-6.58 mg/kg in total) and in vivo (up to 5.01 µg/L in plasma of rats administered with 100 mg/kg bodyweight of rutin). The three adducts discovered were assigned as 6-(1,2-propanedione)-8-(1-acetol)-rutin, 6-(1-acetol)-8-(1,2-propanedione)-rutin, and 6-(1,2-propanedione)-8-(1,2-propanedione)-rutin. Cytotoxicity evaluation in different cell lines indicated that the formation of these rutin-MGO adducts remarkably reduced the toxicity of MGO, which provide further promise for the application of rutin as a scavenger of dicarbonyl compounds by dietary supplement and addition in foods.

Glycine and serine markedly eliminate methylglyoxal in the presence of formaldehyde via the formation of imidazole salts.

l-glycine and l-serine are the building blocks of proteins and exhibit various biological activities. This work found that l-glycine and l-serine show low scavenging capacity for methylglyoxal at moderate conditions (pH 7.0, 37 °C). However, they efficiently eliminate methylglyoxal and formaldehyde when the two aldehydes co-exist, via generation of imidazole salt, a compound formed by one molecule of methylglyoxal and formaldehyde, and two molecules of amino acids. The imidazole salts were identified in biscuits and fried potato crisps. Moreover, the formation of imidazole salts greatly decreased the cytotoxicity of their precursors, methylglyoxal and formaldehydes. This finding suggests that glycine and serine can be used to scavenge these two harmful aldehydes both after intake and during food processing.

Design of a naphthalimide-based probe for acrolein detection in foods and cells.

Acrolein is a highly toxic agent that can be generated exogenously and endogenously. Therefore, a highly specific and sensitive probe for acrolein with potential applications in acrolein detection must be developed. In this research, a novel fluorescent probe named "probe for acrolein detection" (Pr-ACR) was designed and synthesized based on a naphthalimide fluorophore skeleton, and a thiol group (-SH) was introduced into its structure for acrolein recognition. The -SH traps acrolein via Michael addition and the resultant interaction product of the probe inhibits the photoinduced electron transfer process and produce a strong fluorescence at 510 nm. The probe showed high sensitivity and specificity for acrolein. HPLC-MS/MS analysis verified that it can be used to quantify acrolein in foods, such as soda crackers, red wine, and baijiu, with a fluorescence spectrophotometer. After methyl esterification, the methyl esterified probe (mPr-ACR) successfully visualised acrolein in Hela cells under a laser scanning confocal microscope. This finding proved that Pr-ACR and mPr-ACR are potential tools for the detection and visualisation of acrolein from different sources.

Identification of adducts formed between acrolein and alanine or serine in fried potato crisps and the cytotoxicity-lowering effect of acrolein in three cell lines.

In physiological and thermally-processed conditions, alanine and serine efficiently eliminate acrolein to generate two main adducts, 2-(5-formyl-3,6-dihydropyridin-1(2H)-yl) propanoic acid and 2-(5-formyl-3,6-dihydropyridin-1(2H)-yl)-3-hydroxypropanoic acid, with amounts of 81.6 ± 4.24 µg/kg and 23.72 ± 0.40 µg/kg in fried potato crisps, respectively. Adduct formation markedly decreased the cytotoxicity of acrolein against Caco-2, GES-1 and HUVEC cells. The cell viability of them remained approximately100% after incubation with 200 µmolL-1 adducts, while the IC50 values for acrolein in the three cells were 66, 54, and 16 µmolL-1 respectively. The adducts express the protective effects by tremendous reduction of cell apoptosis, reactive oxygen species (ROS) production, and DNA damage.

Cytotoxicity of adducts formed between quercetin and methylglyoxal in PC-12 cells.

Quercetin (Que) or quercetin-containing food stuffs are widely incorporated in bakery foods for improving food texture and health effects, and scavenging reactive aldehydes, such as methylglyoxal (MGO) that exhibits various deleterious effects including contribution to neurodegeneration. This study aimed to investigate the cytotoxicity of the adducts formed between quercetin and MGO resulted from the incorporation of quercetin in foods. Two highly-purified adducts (Que-mono-MGO and Que-di-MGO) were found to display higher cytotoxicity than their precursor MGO and quercetin. They elevated apoptosis via upregulation of expression of apoptotic markers, including p-P38, cleaved caspase-9 and -3, and pro-apoptotic Bax. They induced mitochondrial dysfunction via decreasing mitochondrial membrane potential and increasing lactate dehydrogenase release. Moreover, they attenuated levels of p-Akt, Nrf2, NQO-1, and HO-1, proving that they induced neurodegeneration apoptosis through mitochondria-mediated signaling pathways (PI3K-Akt and Nrf2-HO-1/NQO-1). These findings indicated that the safety consequence of MGO after scavenged by polyphenols needs to be concerned.

Water-in-Oil Pickering Emulsions Stabilized Solely by Water-Dispersible Phytosterol Particles.

Water-in-oil (W/O) Pickering emulsions were successfully synthesized by water-dispersible phytosterol (PS) particles formed through simple antisolvent precipitation. The effects of the organic/aqueous ratio on the particle morphology, crystallinity, and contact angle were investigated. Sheet-like PS particles with reduced crystallinity were further used as W/O Pickering emulsion stabilizers. The properties of the formed W/O emulsions could be transformed by changing the oil type, water-phase fraction, or particle contents. Results showed that emulsions with 80% water fraction could be stabilized by 3% particles in the aqueous phase, where dodecane was used as the oil phase. W/O Pickering emulsions stabilized by PS particles showed temperature responsiveness. When dried, PS particles could be well dispersed either in the water or oil phase to stabilize W/O Pickering emulsions. Therefore, this kind of PS particles could not only enrich the family of food-grade Pickering stabilizers, especially the W/O type, but also provide a smart Pickering stabilizer to fabricate environmental-responsive emulsion products.

Formation and Identification of Two Hydroxmethylfurfural-Glycine Adducts and Their Cytotoxicity and Absorption in Caco-2 Cells.

Our previous research showed that thioacetal and Schiff base formed between 5-hydroxymethylfurfural (HMF) and cysteine or lysine considerably decreased the cytotoxicity of HMF. In this study, two adol condensation adducts, named 2ß-amino-3α-hydroxy-3-(5-(hydroxymethyl)furan-2-yl)propanoic acid (HGA) and 2α-amino-3ß-hydroxy-3-(5-(hydroxymethyl)furan-2-yl)propanoic acid (HGB), were prepared from the reaction products of glycine and HMF, and their cytotoxicities were investigated in Caco-2 cells. Compared with HMF, HGA and HGB displayed lower cytotoxicities against Caco-2 cells with IC50 values of 36.50 and 43.47 mM, respectively, versus 16.11 mM (HMF). In contrast to our findings in thioacetal and Schiff base products, HGA and HGB underwent a very high metabolism rate (99%) in Caco-2 cells. HGA and HGB may degrade to other products instead of HMF since no extracellular or intracellular HMF was detected.

Regulation of phytochemicals in fruits and berries by environmental variation-Sugars and organic acids.

Sugars and organic acids are important phytochemicals contributing to the nutrition and sensory properties of fruits and berries. Their contents are closely correlated to the genetic background of plants as well as to the environmental conditions during growth. This review focuses on the recent researches on the metabolism of these compounds in fruits and berries in response to the variation of environmental conditions, including temperature, radiation, and water supply. A great deal of investigations indicates that the influence of environmental factors on the composition of fruits/berries depended largely on the genetic background. Moreover, the metabolic regulation in response to environmental changes also varies between different plant developmental stages. Nevertheless, some general trends, like the positive correlation between light intensity and sugar content, were observed in most investigations. In grapes (Vitis vinifera L.), the content of malic acid always decreases as light intensity increases, and as the water supply decreases. PRACTICAL APPLICATIONS: The contents of sugars and organic acids, and especially their relative ratio, are important indicators determining the taste and quality of fruits and fruit products. In this review, we summarized the investigations carried out on the regulation of these sensory contributing primary metabolites in fruits and berries in relation to the variation of environmental conditions. It was indicated that various factors, such as plant genotype, growing period, and interaction between environmental factors, might contribute to the impact of environmental changes on the composition of fruits/berries. The article not only provides comprehensive knowledges in food chemistry and plant physiology but also provide important background knowledge for berry cultivation and breeding, as well as useful guidelines for utilization of fruits and berries in food industry.

Adducts formed during protein digestion decreased the toxicity of five carbonyl compounds against Caco-2 cells.

Acrolein (ACR), glyoxal (GO), methylglyoxal (MGO), hydroxymethylfurfural (HMF), and malondialdehyde (MDA) are toxic contaminants for humans. This work aimed to investigate whether intake of proteins can mitigate their toxicity. Simulated gastrointestinal digestion of proteins from pork, chicken, milk powder and soy protein isolate eliminated amount of ACR, GO, MGO, HMF, and MDA. Among six amino acids, cysteine showed highest capacity for elimination of these toxic compounds through the formation of adducts; it reached the highest elimination capacity for GO, MGO, ACR, MDA, and HMF in 40 min at pH 2.0, and 20 min at pH 7.0. The formed adducts between cysteine and GO, MGO, or ACR showed much lower toxicity against Caco-2 cells. Incubation of the cells with 8 mM GO and MGO for 48 h decreased the cell viability to 16.1%, 16.9% respectively; while incubation of the same concentration of their adducts still kept the cell viability at 82.2% and 81.6% respectively. Cysteine showed much higher detoxifying capacity for ACR than GO and MGO, which can lower the toxicity of ACR toward Caco-2 cells by 80 times.

Absorption of 1-Dicysteinethioacetal-5-Hydroxymethylfurfural in Rats and Its Effect on Oxidative Stress and Gut Microbiota.

The absorption of a 5-hydroxymethylfurfural (HMF)-cysteine adduct, 1-dicysteinethioacetal-5-hydroxymethylfurfural (DCH), and its effect on antioxidant activity and gut microbiota were investigated. Results indicated that DCH is more easily absorbed in rats than HMF. Serum DCH concentrations were 15-38-fold of HMF concentrations from 30 to 180 min after intragastrical administration at the level of 100 mg/kg of body weight, and 2.7-4.5% of absorbed DCH was converted to HMF. The malondialdehyde content in the plasma, heart, liver, and kidneys significantly increased after drug (100 mg/kg of bw) administration for 1 week, suggesting that HMF and DCH were oxidative-stress-inducing agents, instead of antioxidant agents, in rats. HMF and DCH also modulated gut microbiota. HMF promoted the growth of Lactobacillus, Tyzzerella, Enterobacter, and Streptococcus. DCH increased the ratio of Firmicutes/ Bacteroidetes and promoted the growth of Akkermansia, Shigella, and Escherichia while inhibiting the growth of Lactobacillus.

The Formation of Acrylamide from and Its Reduction by 3-Aminopropanamide Occur Simultaneously During Thermal Treatment.

3-Aminopropanamide (3-APA) is the direct precursor of acrylamide produced in the Maillard reaction between asparagine and reducing sugars. In this research, we found that 3-APA could reduce acrylamide by the formation of adducts between acrylamide and 3-APA via Michael addition. The effects of temperature, heating duration and 3-APA/acrylamide ratio on the reduction of acrylamide were investigated. Addition of 3-APA to acrylamide at a molar ratio of 5:3 at 160 °C for 20 min reduced acrylamide by up to 47.29%. The major adduct was identified as 3,3',3'-nitrilotris, and its cytotoxicity on Caco-2 cells was evaluated to be much lower than acrylamide. The viability of Caco-2 cells retained at 88.31% and 86.43% after incubation with 16 mM 3,3',3'-nitrilotris for 24 and 48 hr, respectively, while those incubated with the same concentration of acrylamide were 23.33% and 19.12%, respectively. PRACTICAL APPLICATION: The current study reported 3-APA could reduce acrylamide through the Micheal addition reaction between 3-APA and acrylamide. The adduct showed significantly reduced cytotoxicity compared to acrylamide. The research is critical in evaluation and control of food contaminants. The results brought new insights in the area of food safety, especially in the mechanism researches on formation and mitigation of endogenous contaminants in thermal-processed foods.

Formation of a Hydroxymethylfurfural-Cysteine Adduct and Its Absorption and Cytotoxicity in Caco-2 Cells.

Adducts of 5-hydroxymethylfurfural (HMF)-amino acids are formed during food processing and digestion; the elimination capacity of in vitro intestinal digests of biscuits, instant noodles, and potato crisps for HMF is 652, 727, and 540 µg/g, respectively. However, the safety of these adducts is unknown. In this study, an HMF-cysteine adduct named 1-dicysteinethioacetal-5-hydroxymehtylfurfural (DCH), which was found to be produced in the gastrointestinal tract after HMF intake, was prepared to test its effect toward Caco-2 cells. Compared with HMF, the adduct displayed lower cytotoxicity against Caco-2 cells with an IC50 value of 31.26 mM versus 14.95 mM (HMF). The DCH did not induce cell apoptosis, whereas HMF significantly increased the apoptosis rate after incubation at concentrations of 16, 32, and 48 mM for 72 h. DCH showed an absorption rate considerably lower than that of HMF by Caco-2 cells. Lower absorption of DCH may result in lower toxicity compared with HMF against Caco-2 cells. Intracellular transformation of DCH has been observed.