Epoxyalkenal-trapping ability of phenolic compounds

Alkylresorcinols trap malondialdehyde in whole grain crackers

To study the alkylresorcinols ability to trap lipid oxidation products in foods, crackers were prepared with either whole grain rye, wheat, spelt, or oat flour, and either sunflower or linseed oil, and were stored for up to 36 days at room temperature. During storage, polyunsaturated fatty acyl chains degraded, malondialdehyde was produced, and alkylresorcinol content decreased. At the end of the storage, alkylresorcinol content in crackers was reduced by 61-78 % and a part of disappeared alkyresorcinols (3-8 %) appeared as malondialdehyde/alkylresorcinol adducts. Formed adducts were unambiguously identified by using synthesized and characterized (NMR, MS) labelled and unlabelled standards, and determined by LC-MS/MS. This ability of alkylresorcinols to trap malondialdehyde, and most likely other lipid oxidation products, might be playing a role in both the reduction of hazardous reactive carbonyls in whole grain foodstuffs and the observed flavor differences between whole and refined grain food products.

A Comparative Study of the Inhibitory Effect of Some Flavonoids and a Conjugate of Taxifolin with Glyoxylic Acid on the Oxidative Burst of Neutrophils

During the storage, processing, and digestion of flavonoid-rich foods and beverages, a condensation of flavonoids with toxic carbonyl compounds occurs. The effect of the resulting products on cells remains largely unknown. The aim of the present study was to evaluate the effects of quercetin, taxifolin, catechin, eriodictyol, hesperetin, naringenin, and a condensation product of taxifolin with glyoxylic acid on the oxidative burst of neutrophils. It was found that the flavonoids and the condensation product inhibited the total production of ROS. Flavonoids decreased both the intra and extracellular ROS production. The condensation product had no effect on intracellular ROS production but effectively inhibited the extracellular production of ROS. Thus, the condensation of flavonoids with toxic carbonyl compounds may lead to the formation of compounds exhibiting potent inhibitory effects on the oxidative burst of neutrophils. The data also suggest that, during these reactions, the influence of a fraction of flavonoids and their polyphenolic derivatives on cellular functions may change. On the whole, the results of the study provide a better understanding of the effects of polyphenols on human health. In addition, these results reveal the structure-activity relationship of these polyphenols and may be useful in a search for new therapeutic agents against diseases associated with oxidative stress.

Effect of fiber-bound polyphenols from highland barley on lipid oxidation products of cooked pork during in vitro gastrointestinal digestion

BACKGROUND

The gastrointestinal (GI) tract is a major site of lipid oxidation, and the lipid oxidation products are related to an increased risk of various chronic diseases. In this study, the inhibition capacity of bound-polyphenol rich insoluble dietary fiber (BP-IDF) from highland barley (HB) to lipid oxidation was evaluated during simulated GI digestion.

RESULTS

We found that the level of lipid hydroperoxides (LOOH) and aldehydes were significantly inhibited when highland barley bound-polyphenol rich insoluble dietary fiber (HBBP-IDF) co-digestion with cooked pork. The lipid oxidation products were more effectively scavenged during simulated gastric digestion, with inhibition of 77.4% for LOOH, 52.3% for malondialdehyde, 46.5% for 4-hydroxy-2-hexenal and 48.7% for 4-hydroxy-2-nonenel, respectively. The fiber-bound polyphenols are the principal scavengers of lipid oxidation products.

CONCLUSION

These findings suggest that HBBP-IDF could be used as a functional ingredient able to scavenge lipid oxidation products across the GI tract. © 2023 Society of Chemical Industry.

Malondialdehyde trapping by food phenolics

The reactions between malondialdehyde and 2,5-dimethylresorcinol, orcinol, olivetol, and alkylresocinols were studied in an attempt to investigate both if this lipid oxidation product is trapped by phenolics analogously to other reactive carbonyls and to elucidate the chemical structures of the produced adducts. After being formed, malondialdehyde is both partially fractionated to acetaldehyde and oligomerized into dimers and trimers. All these compounds react with phenolics producing three main kinds of derivatives: 5(or 7)-alkyl-7(or 5)-hydroxy-4-methyl-4H-chromene-3-carbaldehydes, 7-alkyl-9-hydroxy-6H-2,6-methanobenzo[d][1,3]dioxocine-5-carbaldehydes, and 4-(3-formylphenyl)-7-hydroxy-4H-chromene-3-carbaldehydes. A total of twenty-four adducts were isolated by semipreparative high-performance liquid chromatography (HPLC) and characterized by mono- and bi-dimensional nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). Reaction pathways to explain the formation of all these compounds are proposed. Obtained results show that phenolics can trap malondialdehyde producing stable derivatives. The function(s) that such derivatives can play in foods remain(s) to be elucidated.

Comparison of Antioxidant Properties of a Conjugate of Taxifolin with Glyoxylic Acid and Selected Flavonoids

It is known that flavonoids can react with toxic carbonyl compounds in the process of the storage, aging, and digestion of flavonoid-rich foods and beverages. However, the effect of these reactions on the antioxidant properties of the polyphenolic fraction and the properties of the resulting products remain poorly studied. The aim of the present work was to study the antioxidant activity of quercetin, taxifolin, catechin, eriodictyol, hesperetin, naringenin and a product of the condensation of taxifolin with glyoxylic acid, as well as to reveal the structure–activity relationship of these polyphenols. It was found that flavonoids containing the catechol moiety exhibited higher antioxidant activity than hesperetin and naringenin. The product showed the highest hydrogen peroxide scavenging activity, a lower metal-reducing and a higher iron-binding ability than catechol-containing flavonoids, and a lipid peroxidation inhibitory activity comparable with that of taxifolin. Thus, the condensation of flavonoids with toxic carbonyl compounds might lead to the formation of products exhibiting high antioxidant activity. Meanwhile, the conditions under which parent flavonoids and their products exhibit the maximal antioxidant activity may differ. The data suggest that the antioxidant profile of the polyphenolic fraction and bioavailability of polyphenols, carbonyl compounds, and metal ions may change when these reactions occur.

Formation of heterocyclic aromatic amines with the structure of aminoimidazoazarenes in food products

Thermal food processing has many beneficial consequences, although it also produces some unintentional undesired effects, such as the formation of potentially mutagenic and carcinogenic substances. Among them, the formation of heterocyclic aromatic amines (HAAs) has been related to the declared carcinogenicity of processed meats. In spite of this importance, HAA formation pathways remain mostly unknown, which avoids the design of targeted procedures to inhibit HAA appearance. The objective of this review is to collect information recently appeared that allow advancing in the understanding of how these compounds are produced. Particularly, the possibility that aminoimidazoazarenes are produced similarly to PhIP is discussed, including their formation by cyclizations and oligomerizations of aldehydes and creatinine under usual cooking conditions. Present data suggest that HAA formation might be related to the pool of carbonyl compounds existing in foods, the food carbonylome, which can be controlled by carbonyl-trapping agents, such as amine and phenolic compounds.

Effects of hydroxycinnamic acids on the reduction of furan and α-dicarbonyl compounds

The effects of hydroxycinnamic acids such as cinnamic acid (CNA), p-coumaric acid(CMA), caffeic acid (CFA), and chlorogenic acid (CGA) on the reduction of furan in canned-coffee model systems (CCMS) containing α-dicarbonyls [glyoxal (GO) or methylglyoxal (MGO)] were investigated. The concentration of furan in CCMS containing GO, which was 59.76 μg/L, was reduced by the addition of CFA and CGA to 48.31 μg/L and 41.38 μg/L, respectively; similarly, the furan concentration in model system containing MGO was 45.79 μg/L, and this decreased to 35.41 μg/L (by CFA) and 32.65 μg/L (by CGA), respectively. In addition, the effects of hydroxycinnamic acids on the trapping of GO and MGO were determined. CFA and CGA greatly reduced the concentration of GO to 303.51 μg/L and 267.80 μg/L, respectively (compared to 515.79 μg/L in the control), whereas that of MGO was decreased to 207.01 μg/L and 219.14 μg/L (compared to 417.14 μg/L in the control). The trapping of α-dicarbonyls such as GO and MGO by CFA and CGA could be closely related to furan reduction in CCMS.

Characterization of Carbonyl-Phenol Adducts Produced by Food Phenolic Trapping of 4-Hydroxy-2-hexenal and 4-Hydroxy-2-nonenal

4-Hydroxy-2-alkenals disappear in the presence of food phenolics (i.e., cathechin or quercetin), and the corresponding carbonyl-phenol adducts are produced. In an attempt to identify structure(s) of formed adducts, the reactions between model phenolics (resorcinol, 2-methylresorcinol, orcinol, and 2,5-dimethylresorcinol) and hydroxyalkenals (4-hydroxy-2-hexenal and 4-hydroxy-2-nonenal) were studied and the produced adducts were isolated by column chromatography and unambiguously characterized by one- and two-dimensional nuclear magnetic resonance and mass spectrometry as dihydrobenzofuranols (1), chromane-2,7-diols (2), and 2 H-chromen-7-ols (3). These compounds were mainly produced at slightly basic pH values and moderate temperatures. Their activation energies ( E_a) of formation were ∼25 kJ mol^-1 for adducts 1, ∼32 kJ mol^-1 for adducts 2, and ∼38 kJ mol^-1 for adducts 3. A reaction pathway that explains their formation is proposed. All of these results confirm that, analogously to other lipid-derived carbonyl compounds, phenolics can trap 4-hydroxy-2-alkenals in an efficient way. Obtained results provide the basis for the potential detection of carbonyl-phenol adducts derived from hydroxyalkenals in food products.

Carbonyl-Phenol Adducts: An Alternative Sink for Reactive and Potentially Toxic Lipid Oxidation Products

Different from the well-characterized function of phenolics as antioxidants, their function as lipid-derived carbonyl scavengers is mostly unknown. However, phenolics react with lipid-derived carbonyls as a function of the nucleophilicity of their reactive groups and the electronic effects and steric hindrances present in the reactive carbonyls. Furthermore, the reaction produces a wide variety of carbonyl-phenol adducts, some of which are stable and have been isolated and characterized but others polymerize spontaneously. This perspective updates present knowledge about the lipid-derived carbonyl trapping ability of phenolics, its competition with carbonyl-amine reactions produced in foods, and the presence of carbonyl-phenol adducts in food products.