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.

Effect of Sequential Inoculation of Tetragenococcus halophilus and Wickerhamomyces anomalus on the Flavour Formation of Early-Stage Moromi Fermented at a Lower Temperature.

Microbial inoculation in moromi fermentation has a great influence on the physicochemical and flavour properties of soy sauces. This work investigated the effect of inoculating Tetragenococcus halophilus and Wickerhamomyces anomalus on the flavour formation of early-stage moromi (30 days) fermented at a lower temperature (22 °C) by determining their physicochemical and aroma changes. The results showed that single yeast or LAB inoculation increased the production of amino nitrogen, lactic acid and acetic acid, as well as free amino acids and key flavour components. Particularly, the sequential inoculation of T. halophilus and W. anomalus produced more free amino acids and aromatic compounds, and there might be synergistic effects between these two strains. More characteristic soy sauce flavour compounds, such as benzaldehyde, HEMF, guaiacol and methyl maltol were detected in the sequentially inoculated moromi, and this sample showed higher scores in savoury, roasted and caramel intensities. These results confirmed that sequential inoculation of T. halophilus and W. anomalus could be a choice for the future production of moromi with good flavour and quality under a lower temperature.

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.

Dietary phytochemical and metabolic disease prevention: Focus on plant proteins.

Plant-based functional foods have attracted increasing research interest to validate their use in preventing metabolic disease. Since it is increasingly recognized that inflammation, oxidative stress, and circadian rhythm play vital roles in various metabolic diseases, including diabetes, obesity and non-alcoholic liver disease, plant proteins, protein hydrolysates, and food extracts that intervene in these biological processes are promising dietary supplements to prevent metabolic diseases. Here, we reviewed the recent research on plant-based foods used for metabolic disease prevention and provided new perspectives regarding the current study gaps and future directions in this field.

Reduction in Five Harmful Substances in Fried Potato Chips by Pre-Soaking Treatment with Different Tea Extracts.

Thermally processed food always contains various types of harmful substances. Control of their levels in food is important for human health. This work used the extracts from green tea dust, old green tea, yellow tea, white tea, oolong tea, and black tea to simultaneously mitigate diverse harmful substances in fried potato chips. The six tea extracts (30 g/L) all showed considerable inhibitory effects on the formation of 5-hydroxymethylfurfural (reduced by 19.8%-53.2%), glyoxal (26.9%-36.6%), and methylglyoxal (16.1%-75.1%). Green tea and black tea extracts exhibited better inhibitory abilities than the other three teas and were further investigated for other harmful compounds by various concentration treatments. Finally, pre-soaking of fresh potato slices in 50 g/L extracts of green tea dust displayed, overall, the most promising inhibitory capacity of HMF (decreased by 73.3%), glyoxal (20.3%), methylglyoxal (69.7%), acrylamide (21.8%), and fluorescent AGEs (42.9%) in fried potato chips, while it exhibited the least impact on the color and texture. The high level of catechins in green tea dust may contribute most to its outstanding inhibitory effect, whereas the distinguished inhibitory effect of black tea extract was speculated to be attributable to the high levels of theaflavins and amino acids in the fully fermented tea. This study indicated that green tea dust, a predominant waste of the tea industry, had great potential to be exploited to improve food quality and safety.

Cytotoxicity of a Novel Compound Produced in Foods via the Reaction of Amino Acids with Acrolein along with Formaldehyde.

Acrolein (ACR) and formaldehyde (FA) are toxic aldehydes co-produced in foods. This work found that amino acids, the nucleophiles ubiquitously existing in foods, can react simultaneously with them. Six amino acids, including γ-aminobutyric acid (GABA), glycine, alanine, serine, threonine, and glutamine, can scavenge ACR and FA at 37, 85, and 160 °C. GABA had the highest scavenging capacity for ACR and FA, by 79 and 13% at 37 °C for 2 h, and 99 and 48% at 160 °C for 30 min, respectively. Moreover, a new type of compound with a basic structure of 5-formyl-3-methylene-3,6-dihydropyridin was identified in all reactions and formed by 1 molecule of FA and amino acid and 2 molecules of ACR. The content of this compound was higher than that of free ACR in typical thermally processed foods. Moreover, the compounds produced from different amino acids showed different cytotoxicity values. In gastric epithelial and human intestinal epithelial cell lines, the cytotoxicity values of serine-sourced and threonine-sourced products were lower than that of ACR but higher than that of FA, whereas others had less toxicity compared with the two aldehydes. Considering that the content of serine-sourced products was the highest in almost all tested foods, their safety needs to be evaluated.

Bioassay-guided isolation of Fenghuang Dancong tea constituents with α-glucosidase inhibition activities.

An α-glucosidase inhibition assay showed the ethanolic extract of Fenghuang Dancong tea had potential α-glucosidase inhibitory activity. The most bioactive fraction, which was obtained via bioassay-guided isolation of the extract, was further purified to create five compounds, including three novel compounds (1-3). These compounds were analyzed and identified in detail using high-resolution-mass spectrometry and extensive one-dimensional and two-dimensional NMR spectroscopy experiments. Among the compounds, compound 1 contained cis double bonds and showed the strongest α-glucosidase inhibitory activity with an IC50 value of 7.51 µM, which is significantly lower than that of compound 2 with trans double bonds. Enzyme kinetic experiments showed that 1 was a reversible non-competitive α-glucosidase inhibitor.

Rutin alleviated acrolein-induced cytotoxicity in Caco-2 and GES-1 cells by forming a cyclic hemiacetal product.

Acrolein (ACR), an α, ß-unsaturated aldehyde, is a toxic compound formed during food processing, and the use of phenolics derived from dietary materials to scavenge ACR is a hot spot. In this study, rutin, a polyphenol widely present in various dietary materials, was used to investigate its capacity to scavenge ACR. It was shown that more than 98% of ACR was eliminated under the conditions of reaction time of 2 h, temperature of 80 °C, and molar ratio of rutin/ACR of 2/1. Further structural characterization of the formed adduct revealed that the adduct of rutin to ACR to form a cyclic hemiacetal compound (RAC) was the main scavenging mechanism. Besides, the stability of RAC during simulated in vitro digestion was evaluated, which showed that more than 83.61% of RAC was remained. Furthermore, the cytotoxicity of RAC against Caco-2 and GES-1 cells was significantly reduced compared with ACR, where the IC50 values of ACR were both below 20 µM while that of RAC were both above 140 µM. And the improvement of the loss of mitochondrial membrane potential (MMP) by RAC might be one of the detoxification pathways. The present study indicated that rutin was one of the potential ACR scavengers among natural polyphenols.

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.

Formation and Identification of a 5-(Hydroxymethyl)-2-Furfural-Zingerone Condensate and Its Cytotoxicity in Caco-2 Cells.

5-(Hydroxymethyl)-2-furfural (HMF), an active furfural, widely exists in various food products and has potential safety risks. It can be eliminated by occurring aldol condensation with α-unsubstituted ketones in the presence of catalysts. However, the elimination process between HMF and ketones from food is rarely studied. In this study, the adduct formation between HMF and zingerone (ZGR) catalyzed by proline was investigated. It revealed that the adduct formation led to 99.75% of HMF being trapped under the optimized reaction condition. Moreover, the in vitro digestion stability of HMF-ZGR adduct (HMZ) and its cytotoxicity against Caco-2 cells were evaluated. The results indicated that more than 75% of HMZ was remained after a three-stage simulated digestion. Following 24 and 48 h of incubation, HMZ exhibited cytotoxicity against Caco-2 cells with IC50 values of 41.47 ± 5.33 and 25.39 ± 3.12 mM, respectively, versus 35.39 ± 4.03 and 19.17 ± 2.10 mM by HMF.

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.

Isolation, structural characterization and anti-oxidant activity of a novel polysaccharide from garlic bolt.

Allium sativum L. is a widely distributed plant used as a spice, vegetable and medicine. In this study, one novel water-soluble polysaccharide (GBP-1a), with a molecular weight of 15.0 kDa, was isolated from the scape of A. sativum (garlic bolt). GBP-1a consists of galactose, glucose and arabinose at a ratio of 73.29:4.36:1.70. It has a backbone, which is composed of 1,4-linked Galp, with 1,2,6-linked Galp branches and 1-linked Glcp residue. In addition, the anti-oxidant activities of GBP-1a, as well as the two main polysaccharide fractions on ABTS radicals, metal ions and superoxide anion radicals, were evaluated in vitro. This study added new data to the study of polysaccharides from garlic bolt.

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.