Malonaldehyde, lipid oxidation

Patton, S. Malonaldehyde, lipid oxidation, and the thiobarbituric acid test. J. Am. Oil Chem. Soc. 51, 114(1974). 

Interaction of lipid oxidation products and amino compounds. Amino acids and primary amines may be involved in other reactions which could lead to the formation of compounds having the potential to undergo N-nitrosation. Malonaldehyde, produced as a result of oxidation of lipids, particularly polyunsaturated fatty acids, has been shown to react with amino acids to produce... 

Kwon, T.-W. and Watts, B.M. 1964. Malonaldehyde in aqueous solution and its role as a measure of lipid oxidation in foods. J. Food Sci. 29 294-302. 

Polyamide microcrystalline powders form measurable polymer-bound fluorescent reaction products with malonaldehyde from oxidizing lipids and with reducing sugars. The compounds form on the terminal amine groups which appear to exist in zwitterionic fields with carboxylate anions, as revealed by titration with acid, alkali, or benzoquinones. 

TBA value Formation of malonaldehyde on oxidation of lipids and its reaction with 2-thiobarbituric acid Gray456... 

In recent years, modern instrumental methods have been developed to monitor lipid oxidation in biological samples, including dairy products. These include use of electron spin resonance (ESR) spectrometry, direct measurement of secondary oxidative products such as malonaldehyde, static and dynamic GC/MS methods. ESR spectrometry permits detection of free radicals formed in the very early stages of oxidation prior to the formation of peroxides. The method has been applied successfully to dairy products such as milk powders and processed cheese (Nielsen et al., 1997 Stapelfeldt... 

Frankel, E.N., Neff, W.E. 1983. Formation of malonaldehyde from lipid oxidation products. 

In particular, this chapter wiU stress the need to look beyond the classic radical chain reaction. Lipid oxidation mechanisms have been proposed based on kinetics, usually of oxygen consumption or appearance of specific products (e.g., LOOK) or carbonyls (e.g., malonaldehyde), assuming standard radical chain reaction sequences. However, when side reactions are ignored or reactions proceed by a pathway different from that being measured, erroneous conclusions can easily be drawn. The same argument holds for catalytic mechanisms, as will be shown in the discussion about metals. In the past, separation and analysis of products was laborious, but contemporary methods allow much more sensitive detection and identification of a broad mix of products. Thus, multiple pathways and reaction tracks need to be evaluated simultaneously to develop an accurate picture of lipid oxidation in model systems, foods, and biological tissues. 

It is important to recognize that scission does not necessarily stop after reaction of initial alkoxyl radicals. Scissions of secondary products generated during lipid oxidation also contribute to propagation and to the ultimate product mix (346). Malonaldehyde is perhaps the best known example of this, as will be discussed further in Section 4.2. 

The thiobarbituric acid (TBA) test was proposed over 40 years ago and is now one of the most extensively used methods to detect oxidative deterioration of fat-containing foods (41). During lipid oxidation, malonaldehyde (MA), a minor component of fatty acids with 3 or more double bonds, is formed as a result of the degradation of polyunsaturated fatty acids. It is usually used as an indicator of the lipid oxidation process, both for the early appearance as oxidation occurs and for the sensitivity of the analytical method (42). In this assay, the MA is reacted with thiobarbituric acid (TBA) to form a pink MA-TBA complex that is measured spectrophotometrically at its absorption maximum at 530-535 nm (Figure 2) (9,43,44). The extent of oxidation is reported as the TBA value and is expressed as milligrams... 

Figure 5. Reaction of lipid oxidation products such as malonaldehyde and amines.

It has been observed that the content of secondary oxidation products, such as malonaldehyde (MA), decreases with increased lipid oxidation, which can be explained by further reaction of MA with proteins. MA reacts with compounds containing primary amino groups (proteins, amino acids, DNA, phospholipids) to form fluorescent products (Figure 5) (37). A fluorescence assay has been successfully used to assess lipid oxidation in muscle foods and biological tissues. 

Malonaldehyde, a typical lipid oxidation product, can form cross-links in proteins by reacting with two amino groups ... 

The ready oxidation of ascorbic acid will catalyze chemical changes in a number of other substances. Thus, unsaturated fatty acids in lecithins and tissues are catalytically oxidized in the presence of ascorbic acid to a substance producing color with thiobarbiturate (B21). The product of the ascorbic acid-catalyzed oxidation is malonaldehyde, which can also inhibit L-gulonolactone oxidase, the enzyme forming ascorbic acid (Cl). It has been suggested that this enzyme inhibition may occur in vivo in animals deficient in vitamin E, a compound believed to have antioxidant actions which would prevent the ascorbic acid-catalyzed lipid oxidation from giving rise to malonaldehyde. It is quite probable that the active intermediate in the formation of malonaldehyde is the monodehydroascorbate radical which initiates the lipid oxidation. 

Another pathway to polymeric products is the cross-linking of lipid or polypeptide chains with bifunctional componnds, such as dicarbonylic lipid oxidation prod-nets (e.g., malonaldehyde) or even with monofunctional carbonylic derivatives such as hexanal. The amount of lipids bonnd by protein may be quite high for example,... 

The thiobarbituric acid (TEA) test is one of the most frequently used methods to assess lipid peroxidation, basically based on the determination of malonaldehyde which is assumed to be an important lipid oxidation product in food and biological systans. ... 

One well studied system is that of the serum low density lipoprotein (LDL sections 5.3.5(e) and 5.5.3). When the lipids of this lipoprotein are peroxidized, the apoprotein becomes fragmented and there is cross-linking and residue modification. Two products of lipid oxidation, malonaldehyde and 4-hydroxy nonenal, are responsible, the latter reacting with lysines of apoprotein-B by an addition reaction. As a result LDL no longer binds to the fibroblast receptor (section 5.5.3) and has an extended half-life in blood. 

The results from the TBA test, known in older literature as the TBA number, are usually expressed as mg malonaldehyde/kg sample for methods a to c cited above (note that results have also been reported as nmol malonaldehyge/kg or g sample) and as mg of malonaldehyde per unit of lipid for method d. Since it is known that malonaldehyde is not the only aldehyde present in the sample extract and because other aldehydes are capable of producing the same red pigment with TBA when the conditions are favorable, the TBA number/value is more appropriately expressed as the TBARS value, i.e., mg malonaldehyde equivalents/kg sample. To confuse the matter, the AOCS method, which is based on the protocol reported by Pokomy and Dieffenbacher (1989) and permits the direct determination of TBA value in oils and fats without preliminary isolation of secondary oxidation products, defines the TBA value as the increase of absorbance measured at 532 nm due to the reaction of the equivalent of 1 mg of sample per 1 ml volume with... 

Chemical Characteristics of the Oxidative Fluorescence-Producing Reaction and Presumptive Implication of Malonaldehyde The reaction producing measurable fluorescence on polyamide powder can be carried out in the gas phase by exposure to the volatiles from oxidizing polyunsaturated lipids, whether acids, esters, triglycerides, or phosphatides. It can be also carried out within either the oil phase or a water emulsion, and, as noted above, it can be followed in the vapor above an emulsion, providing the pH is 5.5 or below. 

In addition, in our hands in the most sensitive fluorescence test for malonaldehyde (acidified, moist p aminobenzoic acid,PABA 26) authentic malonaldehyde from the tetraethoxypropane produces a characteristic intense yellowish-green fluorescence with excitation at 360 nm and emission at 450-460 nm. Oxidizing lipids of the type used in our system show the same fluorescence with PABA. 

Malonaldehyde (MA) is a major end product of oxidizing or rancid lipids and it accumulates in moist foodstuffs (6). Several MA-protein systems have been studied. Chio and Tappel combined RNAase and MA to demonstrate fluorescence attributed to a conjugated imine formed by crosslinking two e-amino groups with the dialdehyde (7). Shin studied the same reaction and found it to be dependent on pH and reactant concentrations (8). Crawford reported the reaction between MA and bovine plasma albumin (BPA) also to be pH dependent, and of first order kinetics with a maximum rate near pH 4.30. At room temperature 50-60% of the e-amino groups were modified—40% in the first eight hours, the remainder over a period of days (9). 

Malonaldehyde, a three-carbon dialdehyde (OHC- -CHO), is produced during lipid peroxidation by the oxidative decomposition of arachi donic and other unsaturated fatty acids. Malonaldehyde is present in a number of food products and its concentration is increased by irradiation of cellular amino acids, carbohydrates, deoxyribose, and DNA. Recent surveys (31-32) have confirmed the presence of malonaldehyde in supermarket samples of meat, poultry, and fish,... 

The antiatherosclerotic effect of proanthocyanidin-rich grape seed extracts was examined in cholesterol-fed rabbits. The proanthocyanidin-rich extracts [0.1% and 1% in diets (w/w)] did not change the serum lipid profile, but reduced the level of the cholesteryl ester hydroperoxides (ChE-OOH) induced by 2,2/-azo-bis(2-amidinopropane-dihydrochloride (AAPH), the aortic malonaldehyde (MDA) content and severe atherosclerosis. The immuno-histochemical analysis revealed a decrease in the number of the oxidized LDL-positive macrophage-derived foam cells on the atherosclerotic lesions of the aorta in the rabbits fed the proanthocyanidin-rich extract. When the proanthocyanidin-rich extract was administered orally to the rats, proantho-cyanidin was detected in the plasma. In an in vitro experiment using human plasma, the addition of the proanthocyanidin-rich extract to the plasma inhibited the oxidation of cholesteryl linoleate in the LDL, but not in the LDL isolated after the plasma and the extract were incubated in advance. From these results, proanthocyanidins of the major polyphenols in red wine might trap ROSs in the plasma and interstitial fluid of the arterial wall, and consequently display antiatherosclerotic activity by inhibiting the oxidation of the LDL [92]. 

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