Chemistry and biochemistry of 4-hydroxynonenal, malonaldehyde and related aldehydes.

Publisher Summary This chapter describes the malondialdehyde (MDA) as index of lipid peroxidation. The determination of malondialdehyde (MDA) has attracted widespread interest, because it appears to offer a facile means of assessing lipid peroxidation in biological materials. Malondialdehyde occurs in biological materials in free state and in various covalently bound forms. Urine also contains small amounts of MDA adducts with guanine, the phospholipid bases serine and ethanolamine, and other unidentified reactants. Free MDA is a minor and variable excretory product. It is apparent from the occurrence of these derivatives in urine that MDA forms adducts with proteins, nucleic acids, and other substances in vivo, and this compromises the assessment of lipid peroxidation in the tissues based on the determination of free MDA. The pH required for maximum yield of MDA varies among biological materials depending on the nature of the derivatives present. MDA may be generated during hydrolysis by the oxidation of polyunsaturated fatty acids (PUFA) in the sample and by the degradation of preexisting oxidation products. Pigments present in the sample, or generated during hydrolysis, also can interfere in the colorimetric assessment of MDA. These problems, and possibilities for their resolution, are discussed in the chapter.

Malondialdehyde determination as index of lipid peroxidation

A comparative evaluation of thiobarbituric acid methods for the determination of malondialdehyde in biological materials

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Routes of formation and toxic consequences of lipid oxidation products in foods.

Lipid oxidation in foods is one of the major degradative processes responsible for losses in food quality. The oxidation of unsaturated fatty acids results in significant generation of dietary advanced lipid oxidation endproducts (ALEs) which are in part cytotoxic and genotoxic compounds. The gastrointestinal tract is constantly exposed to dietary oxidized food compounds, after digestion a part of them are absorbed into the lymph or directly into the blood stream. After ingestion of oxidized fats animals and human have been shown to excrete in urine increase amounts of malondialdehyde but also lipophilic carbonyl compounds. Oxidized cholesterol in the diet was found to be a source of oxidized lipoproteins in human serum. Some of the dietary ALEs, which are absorbed from the gut to the circulatory system, seems to act as injurious chemicals that activate an inflammatory response which affects not only circulatory system but also organs such as liver, kidney, lung, and the gut itself. We believe that repeated consumption of oxidized fat in the diet poses a chronic threat to human health. High concentration of dietary antioxidants could prevent lipid oxidation and ALEs generation not only in foods but also in stomach condition and thereby potentially decrease absorption of ALEs from the gut. This could explains the health benefit of diets containing large amounts of dietary antioxidants such those present in fruits and vegetables, or products such as red-wine or tea consuming during the meal.

Dietary advanced lipid oxidation endproducts are risk factors to human health.

Urinary malondialdehyde (MDA), an indicator of lipid peroxidation in the diat and in the tissues, was determined in human adults consuming a supplement of n-3 fatty acids derived from a pharmaceutical grade of cod liver oil (CLO) without added antioxidants vs a concentrate of n-3 acids containing dodecyl gallate and vitamin E. MDA excretion increased immediately in the subjects consuming CLO but remained unchanged in those ingesting the concentrate for 50 days. The increase in the subjects taking CLO was attributable to MDA in the oil. The results indicate that consuming unstabilized fish oils as a source of n-3 fatty acids may entail exposure to potentially toxic products of lipid peroxidation.

Malondialdehyde excretion by subjects consuming cod liver oil vs a concentrate of n-3 fatty acids.

The form(s) in which malondialdehyde (MDA), a mutagenic product of the oxidative decomposition of polyunsaturated fatty acids (PUFA), occurs in foods was investigated. Several foods of animal origin (ground beef, smoked fish, chicken, sausages) were digested in vitro using pepsin and porcine intestinal fluid and the occurrence of MDA derivatives in the digesta was investigated by thin-layer, column and high-performance liquid chromatography. The predominant form of MDA was shown to be identical to synthetic N-epsilon-propenal lysine. This compound is apparently formed by a reaction between free MDA generated as a product of the oxidative rancidity of PUFA in foods and the free epsilon-amino groups of proteins, from which it is released in the course of digestion. It has been shown to be excreted in rat and human urine partially in the unchanged form and partially as the N-alpha-acetyl derivative. The results of this study serve to mitigate concern over the possible carcinogenicity of MDA in the diet, since less than 10% of the MDA in several foods containing highly unsaturated fatty acids was found in the free form.

Identification of N-ɛ-(2-propenal)lysine as the main form of malondialdehyde in food digesta

Malondialdehyde (MDA) is one of several decomposition products of lipid peroxides formed in fats and oils, in food, and in the tissues. It is the most extensively investigated of these products because of its reactivity with a range of biological macromolecules and its association with the pathophysiology of a number of disease states. MDA is formed enzymatically as a product of the cyclooxygenase reaction in prostaglandin and thromboxane synthesis. There is undoubtedly some free MDA in foods, as indicated by its collection as a volatile product of cooking, but the amount present is difficult to determine because of its artifactual formation. MDA derivatives excreted in the urine are of interest as possible indicators of the forms of MDA in the diet and of the nature of its reactions in vivo. An MDA-cross-linked glycine-adenine adduct was obtained by reacting the enaminal of 9-ethyladenine with glycine methyl ester, indicating that MDA-mediated amino acid-nucleic acid cross-links may occur in vivo.

L. A. Piche

Papers

Malondialdehyde excretion by subjects consuming cod liver oil vs a concentrate of n-3 fatty acids.

Identification of N-ɛ-(2-propenal)lysine as the main form of malondialdehyde in food digesta

Malondialdehyde in Biological Systems