2,4-Alkadienal trapping by phenolics

Formation of the toxic furan metabolite 2-butene-1,4-dial through hemin-induced degradation of 2,4-alkadienals in fried foods

BACKGROUND

The mechanism of protein modification by 2,4-alkadienals (ADE), lipid peroxidation products prevalent in fried foods, was investigated through model reactions.

RESULTS

A mixture of 2,4-heptadienal (HDE) and hemin was initially incubated at pH 3.0-7.4, followed by treatment with acetyl-cysteine (AcCys) and acetyl-lysine (AcLys) at pH 7.4. Analysis via HPLC revealed a product with a characteristic UV spectrum as the primary peak. This product was identified as an AcCys-pyrrole-AcLys (CPL) crosslink derived from AcCys, 2-butene-1,4-dial (BDA), and AcLys. Increasing the HDE concentration in the initial reaction led to maximum CPL formation at pH 3.5 in the presence of hemin. Lowering the HDE concentration with a higher Cys/HDE ratio resulted in CPL formation, which was observed at pH 7.4 and 3.5 in the presence of hemin. Upon incubation of ADE and hemin at pH 3.0-3.5, BDA was directly identified as 2,4-dinitrophenylhydrazone. BDA was also detected in the 2,4-decadienal reaction mixture. Additionally, a notable propensity for high BDA-dC adduct formation with hemin under acidic conditions was observed, consistent with the results of CPL assay and BDA-2,4-dinitrophenylhydrazone analysis.

CONCLUSIONS

1) BDA is efficiently generated from ADE in the presence of hemin under gastric conditions, and 2) BDA-derived CPL can also form under physiological conditions (pH 7.4) through the interaction of ADE, hemin, Cys, and Lys. BDA is recognized as the primary reactive metabolite of the suspected carcinogen furan (IARC, 2B). Given that human intake of ADE exceeds that of furan and acrylamide (IARC 2A) by several orders of magnitude, and the estimated hemin concentration in the stomach post-meal is comparable to the present study, a substantial amount of BDA may form in the stomach following consumption of fried foods and meat. The risk assessment of ADE warrants a thorough re-evaluation, based on the toxicity mechanism of BDA.

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.

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.

Phytochemical-Rich Antioxidant Extracts of Vaccinium Vitis-idaea L. Leaves Inhibit the Formation of Toxic Maillard Reaction Products in Food Models

Thermal treatment of proteinaceous foods generates heat-induced Maillard reaction substances including toxic advanced glycation end products (AGEs) and heterocyclic amines (HAs). It is known that plant phenolic compounds may influence Maillard reaction. This study investigated the impact of lingonberry leaf extracts on the formation of N^ε -(carboxymethyl)lysine (CML) and N^ε -(2-furoylmethyl)-L-lysine (furosine) in milk model system and HAs in meat-protein and meat model systems. In addition, lingonberry leaf extracts obtained by different solvents were characterized by radical scavenging, Folin-Ciocalteu assays and ultrahigh pressure liquid chromatography quadruple-time-of flight mass spectrometry (UPLC-qTOF-MS). Water extract (WE) stronger suppressed CML than furosine formation in milk model system: CML levels were reduced by nearly 40%. Moreover, quinic acid and catechin, which were abundant in WE, were effective in inhibiting CML and furosine formation. WE and acetone extract (AE) at 10 mg/mL significantly inhibited HAs formation in both model systems. However, higher suppressing effect on HAs formation showed AE, which had lower antioxidant capacity and total phenolic content values than WE. WE contained higher amounts of hydroxycinnamic acids, proanthocyanidins and flavonols, while AE was richer in flavan-3-ols and arbutin derivatives. It indicates that the composition of phenolics might be a major factor for explaining different effect of extracts from the same plant on HAs formation. In general, the results suggest that lingonberry leaves is a promising source of phytochemicals for inhibiting toxic Maillard reaction products and enriching foods with plant bioactive compounds. PRACTICAL APPLICATION: The increased consumption in processed foods has been linked with the increased risks of various diseases, while thermal food processing is required to develop flavor, insure safety, and extend shelf life. Therefore, developing effective technological means for inhibiting the formation of heat-induced toxic substances is an important task. This study showed a potential of lingonberry leaf extracts containing health beneficial phytochemicals to suppress the formation of toxic Maillard reaction products during heating of milk and meat.

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.