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

Formation of adducts during digestion triggered dietary protein for alleviating cytotoxicity of 2-tert-butyl-1,4-benzoquinone

2-tert-butyl-1,4-benzoquinone (TBBQ), a degradation product of lipid antioxidant Tert-Butylhydroquinone (TBHQ), is a new hazardous compound in foods. This study investigated whether co-ingestion of dietary protein and TBBQ can alleviate the toxicity of TBBQ. The results indicated that soy protein isolate, whey protein isolate, and rice protein significantly reduced the residual amount of TBBQ during simulated gastrointestinal digestion. This result was attributed to the excellent elimination capacity of the released amino acids for TBBQ through formation of adducts. Among 20 amino acids, histidine, lysine, glycine, and cysteine showed better elimination capacity for TBBQ; they can eliminate 92.1%, 89.4%, 86.1%, and almost 100%, respectively, in 5 min at pH 8.0. Further study indicated that amino acids with lower ionization constant exhibited greater TBBQ elimination capacity. In addition, incubation of the cells with 50 μM TBBQ for 12 h decreased the cell viability to 28.95 ± 3.25%; while amino acids intervention was involved in the alleviation of TBBQ cytotoxicity via decreasing ROS. Particularly, cysteine showed 100 times more TBBQ detoxifying capacity than other amino acids. This work could provide a theoretical basis for the potential application of amino acids for detoxifying TBBQ in the food industry.

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.

Formation of a bioactive cyclopentenone and its adducts with amino acids in sterilized-fruits and - vegetables baby foods

The formation of the molecule 4,5-dihydroxy-2-cyclopenten-1-one (DHCP) from the thermal treatment of pectin-containing foods was investigated in small-scale laboratory preparation of sterilized vegetable puree (carrot, zucchini and tomato) and fruit puree (peach and mixture of pear and apple) and in commercial baby foods. DHCP attracts attention due to its cytotoxicity as well as potential antiviral and anti-inflammatory effects. However, its effects and the difficulty of its identification in food are mediated in part by the formation of Michael adducts of DHCP with amino acids. The results revealed that DHCP reacted efficiently with cysteine and glutathione, and to a lesser extent with histidine. Mass spectrometry analysis confirmed the formation of adducts of DHCP with amino acids in a model system, being in a real food system difficult to investigate. However, these formed adducts are of potential interest, although it is not known whether they are safe, bioactive or reversible.

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.

5-Hydroxymethylfurfural Exerts Negative Effects on Gastric Mucosal Epithelial Cells by Inducing Oxidative Stress, Apoptosis, and Tight Junction Disruption

5-Hydroxymethylfurfural (5-HMF) is a processing byproduct present in foods that are consumed daily by humans, and the diet is the principal route for human exposure to it. However, its adverse effects on gastric epithelial cells are not fully understood. Based on the half inhibitory concentration value, concentrations of HMF of 2, 4, 8, and 16 mM were selected for this study. After 5-HMF treatment for 24 h, the number of living cells decreased to 89.61 ± 0.48, 77.30 ± 0.57, 58.75 ± 0.36, and 19.61 ± 0.40% of the control, respectively. Apoptosis activated through both the death receptor and mitochondrial pathways was confirmed to be the primary mode of HMF-induced cell death. Further analysis revealed that the reactive oxygen species (ROS) levels in GES-1 cells increased 1.7-6.5 fold after exposure to 5-HMF. Moreover, the inhibition of ROS by N-acetylcysteine blocked HMF-induced apoptosis and cell proliferation suppression, indicating that oxidative stress was important in HMF-induced apoptosis. Besides, after 5-HMF treatment, the gene expressions of occludin and ZO-1 were reduced by 1.1-3.4 fold and 2.0-9.4 fold, respectively. The cell surface morphology and tight junction-related protein expression analysis also revealed the destructive effect of 5-HMF on tight junction integrity. Our research highlights a potential mechanism of HMF-induced toxicity in GES-1 cells and provides additional information on the health risks of 5-HMF exposure to the human gastric epithelium.

Inhibition Mechanism of L-Cysteine on Maillard Reaction by Trapping 5-Hydroxymethylfurfural

The Maillard reaction (MR) can affect the color, flavor, organoleptic properties, and nutritional value of food. Sometimes, MR is undesirable due to lowering the nutrient utilization, producing harmful neo-formed compounds, etc. In this case, it is necessary to control MR. Some chemical substances, such as phenolic acid, vitamins, aminoguanidine, and thiols extracted from garlic or onion, can effectively prevent MR. In this study, L-cysteine (L-cys) was found to inhibit MR after screening 10 sulfhydryl compounds by comparing their ability to mitigate browning. The inhibition mechanism was speculated to be related to the removal of 5-hydroxymethylfurfural (HMF), a key mid-product of MR. The reaction product of HMF and L-cys was identified and named as 1-dicysteinethioacetal-5-hydroxymethylfurfural (DCH) according to the mass spectrum and nuclear magnetic resonance spectrum of the main product. Furthermore, DCH was detected in the glutamic-fructose mixture after L-cys was added. In addition, the production of DCH also increased with the addition of L-cys. It also was worth noting that DCH showed no cell toxicity to RAW 264.7 cells. Moreover, the in vitro assays indicated that DCH had anti-inflammatory and antioxidant activities. In conclusion, L-cys inhibits MR by converting HMF into another adduct DCH with higher safety and health benefits. L-cys has the potential to be applied as an inhibitor to prevent MR during food processing and storage.

Effect of catechin on dietary AGEs absorption and cytotoxicity in Caco-2 cells

Maillard reaction produces advanced glycation end products (AGEs) that endanger human health. This study investigated the protective effect of (+)-catechin (CC) on different types of dietary AGEs absorption and cytotoxicity in Caco-2 cells. Our results showed that CC had higher inhibitory rate on peptide bound-AGEs absorption than free Nɛ-carboxymethyl lysine (CML), which dropped to 36.24% and 32.21% when treated with 20 and 50 μM CC. The reasons might be that CC could repair the loose tight junction (ZO-1) and down-regulation of protein-coupling peptide carrier 1 (PEPT-1) expression in Caco-2 cells which were in accordance with molecular docking results. Additionally, CC could remarkably decreased the protein levels of receptor of AGEs (RAGE), mitogen-activated protein kinases (MAPK) and nuclear factor-kappa B (NF-κB) that detected by western blotting and immunohistochemical staining method. Taken together, these findings demonstrated that CC may inhibit AGEs absorption and protected Caco-2 cells against RAGE-MAPK-NF-κB signaling suppression.

Biotransformation of 5-hydroxymethylfurfural into 2,5-dihydroxymethylfuran by Ganoderma sessile and toxicological assessment of both compounds

Biotransformation has the advantages of low cost and environmental protection and is a preferred method for production of compounds. At present, most 2,5-dihydroxymethylfuran (DHMF) is synthesized by chemical methods. In this study, 12.008 μg/mL DHMF was produced from 9.045 μg/mL 5-hydroxymethylfurfural (5-HMF) with a yield of 1.33 g/g using the crude enzymes from fungus Ganoderma sessile. To elucidate the toxic potential for both compounds, cytotoxicity tests and acute toxicity were evaluated respectively. 5-HMF induced weak cytotoxicity in HCT-8, A549 and SGC-7901 cells and DHMF exerted no cytotoxicity on HCT-8 while induced inhibition proliferation of A549 and SGC-7901 cells. The acute toxicity study showed no mortality happened in any group even at the single dose of 2000 mg/kg body weight. These results suggest it is feasible to convert 5-HMF to DHMF via crude enzymes from fungus G. sessile under mild condition, and that DHMF displays a potential effect of antitumor in vitro with little acute toxicity.

Interaction of Acrylamide, Acrolein, and 5-Hydroxymethylfurfural with Amino Acids and DNA

Acrylamide, acrolein, and 5-hydroxymethylfurfural (HMF) are food-borne toxicants produced during the thermal processing of food. The α,β-unsaturated carbonyl group or aldehyde group in their structure can react easily with the amino, imino, and thiol groups in amino acids, proteins, and DNA via Michael addition and nucleophilic reactions in food and in vivo. This work reviews the interaction pathways of three toxins with amino acids and the cytotoxicity and changes after the digestion and absorption of the resulting adducts. Their interaction with DNA is also discussed. Amino acids ubiquitously exist in foods and are added as nutrients or used to control these food-borne toxicants. Hence, the interaction widely occurring in foods would greatly increase the internal exposure of these toxins and their derived compounds after food intake. This review aims to encourage further investigation on toxin-derived compounds, including their types, exposure levels, toxicities, and pharmacokinetics.

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 2β-amino-3α-hydroxy-3-(5-(hydroxymethyl)furan-2-yl)propanoic acid (HGA) and 2α-amino-3β-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.

Identification of a 5-Hydroxymethylfurfural-Lysine Schiff Base and Its Cytotoxicity in Three Cell Lines

5-Hydroxymethylfurfural (HMF) can undergo the Maillard reaction with amino acids. However, the safety of the products remains unknown. In this study, a HMF-lysine Schiff base named (E)-N⁶-((5'-(hydroxymethyl)furan-2'-yl)methylene)lysine (HML) was identified and detected for the first time in baked foods. HML formation significantly decreased the cytotoxicity (IC₅₀) of HMF against GES-1 cells (81.81 versus 5.02 mM and 73.76 versus 2.94 mM for HML versus HMF at 24 and 48 h, respectively), EA.hy926 cells (86.05 versus 4.85 mM and 77.22 versus 0.71 mM, respectively), and Caco-2 cells (155.77 versus 36.84 mM and 112.70 versus 18.51 mM, respectively). Exposure of Caco-2 cells to HMF at 10.0 mM triggered cell apoptosis of 14.02% (versus 8.54% in the control), whereas exposure to HML at 10-15 mM hardly increased cell apoptosis. Moreover, the absorption capacities of HMF and HML by Caco-2 cells were equivalent (p > 0.05) at 7.23-12.57% after incubation at 2 mM for 30-150 min.

5-Hydroxymethylfurfural (HMF) in Organic Synthesis: A Review of its Recent Applications Towards Fine Chemicals

Background:

5-Hydroxymethylfurfural (5-HMF) is a biomass-derived platform chemical, which can be produced from carbohydrates. In the past decades, 5- HMF has received tremendous attention because of its wide applications in the production of various value-added chemicals, materials and biofuels. The manufacture and the catalytic conversion of 5-HMF to simple industrially-important bulk chemicals have been well reviewed. However, employing 5-HMF as a building block in organic synthesis has never been summarized exclusively, despite the rapid development in this area.

Objective:

The aim of this review is to bring a fresh perspective on the use of 5-HMF in organic synthesis, to the exclusion of already well documented conversion of 5-HMF towards relatively simple molecules such as 2,5-furandicarboxylic acid, 2,5-dimethylfuran and so on notably used as monomers or biofuels.

Conclusion:

As it has been shown throughout this review, 5-HMF has been the object of numerous studies on its use in fine chemical synthesis. Thanks to the presence of different functional groups on this platform chemical, it proved to be an excellent starting material for the preparation of various fine chemicals. The use of this C-6 synthon in novel synthetic routes is appealing, as it allows the incorporation of renewable carbonsources into the final targets.

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.

Elucidation of the Intestinal Absorption Mechanism of Loganin in the Human Intestinal Caco-2 Cell Model

Loganin, iridoid glycosides, is the main bioactive ingredients in the plant Strychnos nux-vomica L. and demonstrates various pharmacological effects, though poor oral bioavailability in rats. In this study, the intestinal absorption mechanism of loganin was investigated using the human intestinal Caco-2 cell monolayer model in both the apical-to-basolateral (A-B) and the basolateral-to-apical (B-A) direction; additionally, transport characteristics were systematically investigated at different concentrations, pHs, temperatures, and potential transporters. The absorption permeability (PappAB) of loganin, which ranged from 12.17 to 14.78 × 10-6cm/s, was high at four tested concentrations (5, 20, 40, and 80μM), while the major permeation mechanism of loganin was found to be passive diffusion with active efflux mediated by multidrug resistance-associated protein (MRP) and breast cancer resistance protein (BCRP). In addition, it was found that loganin was not the substrate of efflux transporter P-glycoprotein (P-gp) since the selective inhibitor (verapamil) of the efflux transporter exhibited little effects on the transport of loganin in the human intestinal Caco-2 cells. Meanwhile, transport from the apical to the basolateral side increased 2.09-fold after addition of a MRP inhibitor and 2.32-fold after addition of a BCRP inhibitor. In summary, our results clearly demonstrate, for the first time, a good permeability of loganin in the human intestinal Caco-2 cell model and elucidate, in detail, the intestinal absorption mechanism and the effects of transporters on iridoid glycosides compounds.

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.

Thermal processing food-related toxicants: a review

Heterocyclic aromatic amines, acrylamide, 5-hydroxymethylfurfural, furan, polycyclic aromatic hydrocarbons, nitrosamines, acrolein, chloropropanols and chloroesters are generated toxicants formed in some foodstuffs, mainly starchy and protein-rich food during thermal treatment such as frying, roasting and baking. The formation of these chemical compounds is associated with development of aromas, colors and flavors. One of the challenges facing the food industry today is to minimize these toxicants without adversely affecting the positive attributes of thermal processing. To achieve this objective, it is essential to have a detailed understanding of the mechanism of formation of these toxicants in processed foods. All reviewed toxicants in that paper are classified as probable, possible or potential human carcinogens and have been proven to be carcinogenic in animal studies. The purpose of that review is to summarize some of the most frequent occurring heat-generated food toxicants during conventional heating, their metabolism and carcinogenicity. Moreover, conventional and microwave heating were also compared as two different heat treatment methods, especially how they change food chemical composition and which thermal food toxicants are formed during specific method.