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1.
Food Chem ; 304: 125284, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31476546

RESUMO

The reactions of different lipid-derived reactive carbonyls with ammonia-producing compounds were studied to investigate the formation of pyridines in foods. 2-Alkyl, 3-alkyl-, and 2,5-dialkylpyiridines were produced by oligomerization of short-chain aldehydes in the presence of ammonia. Thus, acetaldehyde/crotonaldehyde mixtures and 2,4-alkadienals were the main responsible for the formation of 2-alkylpyridines; acrolein or 2,4-alkadienals were needed for the formation of 3-alkylpyridines; and 2-alkenals were responsible for the formation of 2,5-dialkylpyridines. On the contrary, 2,6-dialkylpyridines were produced by cyclization of unsaturated ketones. Reactions pathways for formation of these pyridines are proposed, and confirmed by isotopic labelling experiments. Aldehydes and ketones required for their formation are produced in the course of lipid oxidation. Therefore, pyridine formation seems to be an additional consequence of the lipid oxidation pathway. This new knowledge can employed for the optimization of reactions to achieve the desired targeted flavor generation during food processing.

2.
J Agric Food Chem ; 67(7): 2043-2051, 2019 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-30702290

RESUMO

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 ( Ea) 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.


Assuntos
Aldeídos/química , Catequina/química , Alimentos , Fenol/química , Quercetina/química , Concentração de Íons de Hidrogênio , Peroxidação de Lipídeos , Espectroscopia de Ressonância Magnética , Reação de Maillard , Termodinâmica
3.
J Agric Food Chem ; 2018 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-30501175

RESUMO

Lipid hydroperoxides have been shown to produce amino acid decarboxylations. Because thermal decomposition of lipid hydroperoxides produces free radicals and reactive carbonyls, and phenolic compounds have been shown to scavenger both of them, phenolics are expected to inhibit these reactions and this protection should depend on structures of involved phenolics. In this study, the effect of a wide array of phenolics and their mixtures on 2-phenylethylamine formation by phenylalanine degradation in the presence of the 13-hydroperoxide of linoleic acid (LOOH) was studied. LOOH increased considerably the formation of the amine and phenolics mostly exhibited an inhibitory role that depended on their structure. Thus, 1,3-diphenols decreased the formation of 2-phenylethylamine because of their carbonyl trapping abilities. On the contrary, the inhibition of 1,2- and 1,4-diphenols was lower because they could not trap the reactive carbonyls produced by LOOH decomposition. In addition, their free radical scavenging was likely accompanied by the formation of quinones, which acted as reactive carbonyls. The function of all other phenolics could be calculated by adding the individual functions of the different diphenols present in their structures. In fact, experimental values obtained for both mixtures of phenolics and complex phenolics correlated well with the calculated values obtained from their constituting diphenols. All these results suggest that, when reaction mechanisms are known, it is possible to predict the behavior of complex phenolics based on their structure.

4.
Food Chem ; 263: 89-95, 2018 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-29784333

RESUMO

Phenolics can trap lipid-derived reactive carbonyls as a protective function that diminishes the broadcasting of the lipid oxidative damage to food macromolecules. In an attempt to clarify the trapping of 2,4-alkadienals by phenolics, this study analyzes the reactions of 2,4-hexadienal, 2,4-heptadienal, and 2,4-decadienal with 2-methylresorcinol. These reactions produced (E)-4-(alk-1-en-1-yl)-8-methyl-2,7-bis(prop-1-en-2-yloxy)chromanes, which were isolated and characterized by 1D and 2D NMR and MS. Carbonyl-phenol adduct formation was favored at pH > 7 and moderate temperatures (25-80 °C). Adducts were quantified and shown to be produced as a mixture of diastereomers. Diastereomers 2R,4S plus 2S,4R were formed to a higher extent than diastereomers 2R,4R plus 2S,4S under the different conditions assayed, although activation energies (Ea) for the formation of all of them was mostly the same (∼62 kJ·mol-1). These results show that phenolics can trap 2,4-alkadienals and provide the basis for the later detection of the formed adducts in food pro[ducts.

5.
J Agric Food Chem ; 66(6): 1320-1324, 2018 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-29359932

RESUMO

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.


Assuntos
Aminas/química , Lipídeos/química , Fenóis/química , Animais , Culinária , Análise de Alimentos , Temperatura Alta , Humanos , Lipídeos/toxicidade , Reação de Maillard , Oxirredução
6.
J Agric Food Chem ; 66(1): 255-264, 2018 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-29224335

RESUMO

Phenolics can act as either promoters or inhibitors in 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) formation. In an attempt to clarify the structure-activity relationship (SAR) of phenolics for this reaction, the formation of PhIP in mixtures of phenylalanine, creatinine, 13-hydroperoxide of linoleic acid (LOOH) or 4-oxo-2-nonenal, and a wide array of phenolics was studied in the presence and in the absence of oxygen. The obtained results suggested that those phenolics having a high carbonyl scavenging ability inhibited the formation of PhIP. On the other hand, those phenolics that mainly acted as free radical scavengers and, therefore, were easily converted into quinones promoted the formation of PhIP. Phenolics of the first type were m-diphenols and 1,3,5-triphenols. Phenolics of the second type were o- and p-diphenols. Other phenolics, like 1,2,3- and 1,2,4-triphenols, exhibited a behavior either as carbonyl scavengers or as free radical scavengers depending on ring substitutions. Among the studied derivatives, the presence of a carboxylic or a methoxyl group at certain positions inhibited their behavior as carbonyl scavengers and, therefore, promoted the formation of PhIP. A procedure to classify phenolics as either carbonyl or free radical scavengers is proposed.


Assuntos
Creatinina/química , Imidazóis/química , Peróxidos Lipídicos/química , Oxigênio/química , Fenóis/química , Fenilalanina/química , Estrutura Molecular , Oxirredução , Relação Estrutura-Atividade
7.
Food Chem ; 240: 822-830, 2018 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-28946347

RESUMO

The reaction between 4-oxo-2-alkenals (fumaraldehyde, 4-oxo-2-hexenal, and 4-oxo-2-nonenal) and phenolic compounds (resorcinol and 2-methylresorcinol) was studied to characterize the trapping ability of phenolic compounds for these lipid oxidation products. The reaction occurred rapidly under neutral or slightly basic conditions and different carbonyl-phenol adducts were produced. However, these compounds were unstable and their stabilization had to be achieved by means of either acetylation or reduction with sodium borohydride. Three different kinds of adducts were isolated and characterized by using mass spectrometry (MS) and 1D and 2D nuclear magnetic resonance spectroscopy (NMR). They were benzofuran-6-ols, 2,3,3a,8a-tetrahydrofuro[2,3-b]benzofuran-2,6-diols, and chromane-2,7-diols. Most of them were produced as mixtures of diasteromers and all of them had a carbonyl group in a free form or as hemiacetal. A reaction pathway that explains the formation of these compounds is proposed. These results provide the basis to understand the removal of 4-oxo-2-alkenals by phenolic compounds in foods.


Assuntos
Lipídeos/química , Aldeídos , Oxirredução , Resorcinóis
8.
Food Chem ; 237: 444-452, 2017 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-28764018

RESUMO

Lipid oxidation products have been shown to produce changes in food quality and safety as a consequence of carbonyl-amine reactions. Some of these reactions can be prevented by the use of phenolics, although the lipid-derived carbonyl trapping ability of phenolics is still poorly understood. In an attempt to fill this gap, the reactions of 4,5-epoxy-2-hexenal, 4,5-epoxy-2-heptenal, and 4,5-epoxy-2-decenal, with 2-methylresorcinol and 2,5-dimethylresorcinol were studied. These reactions produced diverse 1,3a,4,9b-tetrahydro-2H-furo[2,3-c]chromene-2,7-diols and 3,4,4a,9a-tetrahydro-1H-pyrano[3,4-b]benzofuran-3,7-diols, which were isolated and characterized by 1D and 2D nuclear magnetic resonance (NMR) and mass spectrometry (MS). The produced epoxyalkenal-phenol reaction was characterized and carbonyl-phenol adducts were produced firstly by epoxide-ring opening initiated by the attack of one phenolic hydroxyl group and, then, by addition of one aromatic phenol carbon to the carbon-carbon double bond of the epoxyalkenal. This reaction rapidly deactivated the most important reactive groups of epoxyalkenals, decreasing in this way their ability to modify amino compounds.


Assuntos
Compostos de Epóxi/análise , Fenóis/química
9.
J Agric Food Chem ; 65(23): 4736-4743, 2017 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-28535050

RESUMO

The reaction among flavor-relevant saturated aldehydes (propanal, 2-methylpropanal, butanal, 2-methylbutanal, 3-methylbutanal, pentanal, hexanal, and glyoxal) and phenolic compounds (resorcinol, 2-methylresorcinol, 2,5-dimethylresorcinol, and orcinol) was studied both to identify and to characterize the formed carbonyl-phenol adducts and to understand the differences in the carbonyl-trapping abilities of phenolic compounds. The obtained results showed that carbonyl-trapping by phenolics is selective and that the formation of carbonyl-phenol adducts depends on the structures of both the phenol and aldehyde involved. In relation to the phenolic derivative, the presence of groups that increase the nucleophilicity of phenolic carbons will increase the carbonyl-trapping ability of these compounds. On the other hand, the presence of groups that increase the steric hindrance of these positions without affecting nucleophilicity will inhibit the reaction. Analogously, the presence of branching at position 2 of the aldehyde will also inhibit the reaction by steric hindrance. All of these results suggest that the addition of phenolics to foods may change food flavor not only because of their sensory properties but also because they can modify the ratio among food odorants by selective reaction of phenolics with determined carbonyl compounds.


Assuntos
Aldeídos/química , Resorcinóis/química , Temperatura Alta , Reação de Maillard , Estrutura Molecular , Fenol/química
10.
Food Chem ; 229: 388-395, 2017 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-28372190

RESUMO

The degradation of phenylalanine initiated by 2-pentenal, 2,4-heptadienal, 4-oxo-2-pentenal, 4,5-epoxy-2-heptenal, or 4,5-epoxy-2-decenal in the presence of phenolic compounds was studied to determine the structure-activity relationship of phenolic compounds on the protection of amino compounds against modifications produced by lipid-derived carbonyls. The obtained results showed that flavan-3-ols were the most efficient phenolic compounds followed by single m-diphenols. The effectiveness of these compounds was found to be related to their ability to trap rapidly the carbonyl compound, avoiding in this way the reaction of the carbonyl compound with the amino acid. The ability of flavan-3-ols for this reaction is suggested to be related to the high electronic density existing in some of the aromatic carbons of their ring A. This is the first report showing that carbonyl-phenol reactions involving lipid-derived reactive carbonyls can be produced more rapidly than carbonyl-amine reactions, therefore providing a satisfactory protection of amino compounds.


Assuntos
Aminas/química , Fenóis/química , Aminoácidos/química , Lipídeos/química , Reação de Maillard , Relação Estrutura-Atividade
11.
J Agric Food Chem ; 64(27): 5583-9, 2016 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-27322490

RESUMO

The lipid-derived carbonyl trapping ability of phenolic compounds under common food processing conditions was studied by determining the presence of carbonyl-phenol adducts in both onions fried in the laboratory and commercially crispy fried onions. Four carbonyl-phenol adducts produced between quercetin and acrolein, crotonaldehyde, or (E)-2-pentenal were prepared and characterized by (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy and high performance liquid chromatography coupled to high resolution mass spectrometry (HPLC-HRMS). The synthesized compounds were 2-(3,4-dihydroxyphenyl)-3,5,8-trihydroxy-9,10-dihydro-4H,8H-pyrano[2,3-f]chromen-4-one (4), 2-(3,4-dihydroxyphenyl)-3,5,8-trihydroxy-10-methyl-9,10-dihydro-4H,8H-pyrano[2,3-f]chromen-4-one (5), 2-(3,4-dihydroxyphenyl)-3,5-dihydroxy-8-methyl-4H,8H-pyrano[2,3-f]chromen-4-one (9), and 2-(3,4-dihydroxyphenyl)-8-ethyl-3,5-dihydroxy-4H,8H-pyrano[2,3-f]chromen-4-one (10). When onions were fried in fresh rapeseed oil spiked with acrolein, crotonaldehyde, and (E)-2-pentenal (2.7 µmol/g of oil), adduct 10 was the major compound produced, and trace amounts of adducts 4 and 5, but not of adduct 9, were also detected. In contrast, compound 4 was the major adduct present in commercially crispy fried onions. Compound 10 was also present to a lower extent, and trace amounts of compound 5, but not of compound 9, were also detected. These data suggested that lipid-derived carbonyl-phenol adducts are formed in food products under standard cooking conditions. They also pointed to a possible protective role of food polyphenols, which might contribute to the removal of toxicologically relevant aldehydes produced during deep-frying, assuming that the formed products are stable during food consumption in the human organism.


Assuntos
Aldeídos/química , Aldeídos/toxicidade , Cebolas/química , Fenóis/química , Óleos Vegetais/química , Culinária , Temperatura Alta , Fenóis/toxicidade , Óleos Vegetais/toxicidade
12.
Food Chem ; 209: 256-61, 2016 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-27173560

RESUMO

The formation of 2-phenylethylamine and phenylacetaldehyde in mixtures of phenylalanine, a lipid oxidation product, and a second amino acid was studied to determine the role of the second amino acid in the degradation of phenylalanine produced by lipid-derived reactive carbonyls. The presence of the second amino acid usually increased the formation of the amine and reduced the formation of the Strecker aldehyde. The reasons for this behaviour seem to be related to the α-amino group and the other functional groups (mainly amino or similar groups) present in the side-chain of the amino acid. These groups are suggested to modify the lipid-derived reactive carbonyl but not the reaction mechanism because the Ea of formation of both 2-phenylethylamine and phenylacetaldehyde remained unchanged in all studied systems. All these results suggest that the amine/aldehyde ratio obtained by amino acid degradation can be modified by adding free amino acids during food formulation.


Assuntos
Acetaldeído/análogos & derivados , Aminoácidos/química , Lipídeos/química , Fenetilaminas/análise , Acetaldeído/análise , Acetaldeído/química , Descarboxilação , Reação de Maillard , Oxirredução , Fenetilaminas/química , Fenilalanina/química
13.
Food Chem ; 194: 1143-8, 2016 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-26471665

RESUMO

The Strecker-type degradation of phenylalanine in the presence of 2-pentanal and phenolic compounds was studied to investigate possible interactions that either promote or inhibit the formation of Strecker aldehydes in food products. Phenylacetaldehyde formation was promoted by 2-pentenal and also by o- and p-diphenols, but not by m-diphenols. This is consequence of the ability of phenolic compounds to be converted into reactive carbonyls and produce the Strecker degradation of the amino acid. When 2-pentenal and phenolic compounds were simultaneously present, an antagonism among them was observed. This antagonism is suggested to be a consequence of the ability of phenolic compounds to either react with both 2-pentenal and phenylacetaldehyde, or compete with other carbonyl compounds for the amino acids, a function that is determined by their structure. All these results suggest that carbonyl-phenol reactions may be used to modulate flavor formation produced in food products by lipid-derived reactive carbonyls.


Assuntos
Aminoácidos/química , Lipídeos/química , Fenóis/química , Reação de Maillard
14.
Crit Rev Food Sci Nutr ; 56(8): 1242-52, 2016 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-25748518

RESUMO

Differently to amino acid degradations produced by carbohydrate-derived reactive carbonyls, amino acid degradations produced by lipid oxidation products are lesser known in spite of being lipid oxidation a major source of reactive carbonyls in food. This article analyzes the conversion of amino acids into Strecker aldehydes, α-keto acids, and amines produced by lipid-derived free radicals and carbonyl compounds, as well as the role of lipid oxidation products on the reactions suffered by these compounds: the formation of Strecker aldehydes and other aldehydes from α-keto acids; the formation of Strecker aldehydes and olefins from amines; the formation of shorter aldehydes from Strecker aldehydes; and the addition reactions suffered by the olefins produced from the amines. The relationships among all these reactions and the effect of reaction conditions on them are discussed. This knowledge should contribute to better control food processing in order to favor the formation of desirable beneficial compounds and to inhibit the production of compounds with deleterious properties.


Assuntos
Aminoácidos/química , Peroxidação de Lipídeos , Aldeídos/química , Aminas/química , Carbono/química , Peróxidos Lipídicos/química , Reação de Maillard , Estireno/química , Termodinâmica
15.
J Agric Food Chem ; 63(36): 8037-43, 2015 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-26189462

RESUMO

Comparative formation of both 2-phenylethylamine and phenylacetaldehyde as a consequence of phenylalanine degradation by carbonyl compounds was studied in an attempt to understand if the amine/aldehyde ratio can be changed as a function of reaction conditions. The assayed carbonyl compounds were selected because of the presence in the chain of both electron-donating and electron-withdrawing groups and included alkenals, alkadienals, epoxyalkenals, oxoalkenals, and hydroxyalkenals as well as lipid hydroperoxides. The obtained results showed that the 2-phenylethylamine/phenylacetaldehyde ratio depended upon both the carbonyls and the reaction conditions. Thus, it can be increased using electron-donating groups in the chain of the carbonyl compound, small amounts of carbonyl compound, low oxygen content, increasing the pH, or increasing the temperature at pH 6. Opposed conditions (use of electron-withdrawing groups in the chain of the carbonyl compound, large amounts of carbonyl compound, high oxygen contents, low pH values, and increasing temperatures at low pH values) would decrease the 2-phenylethylamine/phenylacetaldehyde ratio, and the formation of aldehydes over amines in amino acid degradations would be favored.


Assuntos
Aldeídos/química , Aminas/química , Aminoácidos/química , Lipídeos/química , Descarboxilação , Reação de Maillard , Estrutura Molecular , Oxirredução
16.
Food Chem ; 174: 89-96, 2015 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-25529656

RESUMO

Nucleophilic degradation produced by reactive carbonyls plays a major role in food quality and safety. Nevertheless, these reactions are complex because reactive carbonyls are usually involved in various competitive reactions. This study describes the thermal degradation of 2-alkenals (2-pentenal and 2-octenal) and 2,4-alkadienals (2,4-heptadienal and 2,4-decadienal) in an attempt to both clarify the stability of aldehydes and determine new compounds that might also play a role in nucleophile/aldehyde reactions. The obtained results showed that alkenals and alkadienals decomposed rapidly in the presence of buffer and air to produce formaldehyde, acetaldehyde, and the aldehydes corresponding to the breakage of the carboncarbon double bonds: propanal, hexanal, 2-pentenal, 2-octenal, glyoxal, and fumaraldehyde. The activation energy of double bond breakage was relatively low (∼ 25 kJ/mol) and the yield of alkanals (10-18%) was higher than that of 2-alkenals (∼ 1%). All these results indicate that these reactions should be considered in order to fully understand the range of nucleophile/aldehyde adducts produced.


Assuntos
Aldeídos/química , Lipídeos/química , Temperatura Alta
17.
J Agric Food Chem ; 63(1): 312-8, 2015 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-25537664

RESUMO

The ability of 20 phenolic derivatives to produce the Strecker-type degradation of phenylalanine and phenylglycine methyl ester was studied to investigate both the direct degradation of amino acids and amines by phenolic compounds in the absence of added oxidants and the effect of the number and positions of hydroxyl groups in the aromatic ring of the phenolic compound in relation to its ability to produce carbonyl derivatives from amino compounds. The obtained results showed that polyphenols can produce the Strecker degradation of amino acids and amines in the absence of added oxidants. The only requisite for producing the reaction is the presence of two hydroxyl groups in ortho or para positions. However, the presence of two hydroxyl groups in meta position in an additional aromatic ring can inhibit the Strecker-degrading ability of the hydroxyl groups in ortho or para positions. A reaction pathway that explains all of these findings is proposed. In addition, the effect of reaction conditions on the obtained reaction yields was studied. Activation energies (Ea) for phenylacetaldehyde formation from phenylalanine in the presence of hydroquinone, 1,2,4-trihydroxybenzene, and benzoquinone were 32.9, 31.5, and 28.8 kJ/mol, respectively.


Assuntos
Aminas/química , Aminoácidos/química , Aromatizantes/química , Aditivos Alimentares/química , Fenóis/química , Cinética , Estrutura Molecular
18.
J Agric Food Chem ; 62(49): 12045-51, 2014 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-25418848

RESUMO

The carbonyl-scavenging ability of 2-amino-1-methylbenzimidazole (AMBI) and the heterocyclic aromatic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was investigated in an attempt to identify new routes that can modify the carbonyl content of foods. The reaction of both AMBI and PhIP with 2-alkenals, 2,4-alkadienals, 4-oxo-2-alkenals, 4,5-epoxy-2-alkenals, and 4-hydroxy-2-nonenal produced fluorescent adducts, whose structure was determined for the adduct produced between AMBI and 2-pentenal. This adduct was isolated and identified by one- and two-dimensional nuclear magnetic resonance and high-resolution mass spectrometry as 2,10-dihydro-2-ethyl-10-methylpyrimido[1,2-a]benzimidazole. The formation of these adducts was parallel to the elimination of AMBI and PhIP. The Ea of the reaction between PhIP and 4-oxo-2-nonenal was 27.4 kJ/mol. All these results suggest that 2-aminoimidazoles can be employed to modify the carbonyl content of foods. At the same time and because the reaction produces the disappearance of the amino compound, lipid-derived carbonyl compounds can be employed to eliminate 2-aminoimidazoles, which suggests a new strategy for the elimination of heterocyclic aromatic amines in foods.


Assuntos
Depuradores de Radicais Livres/química , Imidazóis/química , Radicais Livres/química
19.
Food Chem ; 160: 118-26, 2014 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-24799217

RESUMO

The reaction between m-diphenols (resorcinol, 2-methylresorcinol, 2,5-dimethylresorcinol, 3-methylphenol, orcinol, and phloroglucinol) and 2-alkenals (2-pentenal and 2-octenal) was studied in an attempt to understand the chemical pathways involved in the scavenging ability of m-diphenols for the 2-alkenals produced as a consequence of lipid oxidation. Phenols reacted chemically with 2-alkenals producing a number of 2H-chromenols, chromandiols, chromanols, and dihydropyrano[3,2-g]chromenes, which were isolated and identified by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). The identification of all these compounds resulted in the construction of a general pathway for these reactions. These results confirm that the 2-alkenal-scavenging ability of m-diphenols is a consequence of their structure. This is a complex reaction in which many different products are formed. The most stable products were the chromandiols. However, the main reaction products were the 2H-chromenols. These products were unstable and disappeared as a consequence of polymerisation and browning reactions.


Assuntos
Aldeídos/química , Resorcinóis/química , Espectroscopia de Ressonância Magnética , Reação de Maillard , Espectrometria de Massas , Oxirredução
20.
Food Chem ; 155: 74-80, 2014 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-24594156

RESUMO

The formation of formaldehyde from phenylacetaldehyde and phenylalanine, and the contribution of both formaldehyde and ammonia to the production of PhIP from phenylacetaldehyde and creatinine were studied in an attempt to clarify the reaction pathways that produce PhIP. Formaldehyde was produced by thermal degradation of phenylacetaldehyde and, to a lesser extent, also by degradation of phenylalanine, phenylethylamine, styrene, and creatinine. When formaldehyde was added to a mixture of phenylacetaldehyde and creatinine, PhIP yield was multiplied by nineteen. When formaldehyde and ammonia were simultaneously present, PhIP yield was multiplied by fifty and the Ea of the reaction decreased by 61%. All these results point to formaldehyde and ammonia as the two additional reactants required for PhIP formation from both phenylacetaldehyde/creati(ni)ne and phenylalanine/creati(ni)ne mixtures. A general pathway for PhIP formation is proposed. This pathway is suggested to be the main route for PhIP formation in foods.


Assuntos
Acetaldeído/análogos & derivados , Amônia/química , Creatinina/química , Formaldeído/química , Imidazóis/química , Acetaldeído/química , Temperatura Alta , Oxirredução
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