Malon dialdehyde

Following the action of extraordinary stimulants (hypoxic hypoxia, hypoxia + hyperoxia, hypodynamia + hyperthermia), animals demonstrate an accumulation of malonic dialdehyde with a simultaneous fall of antiradical activity of the liver tissue. A preliminary introduction to rats of acetylene amine 3,4,5-tris(morpho-linopropynyl)-l-methylpyrazole 103 and also of tocopherol antioxidant and gutumine antihypoxant averts activation of the lipid peroxidation processes. The inhibition of peroxidation with this agent is mediated by stabilization of ly-zosomal and mitochondrial membranes. Unsaturated amines prevent destruction of the organelle membranes provoked by UV irradiation and incubation at 37°C (pH4.7)(78MIl). 

The free radical damage hypothesis of desiccation injury requires that these various protective mechanisms are unable to detoxify reactive species during dehydration and rehydration. There is evidence that free radicals increase with decreasing moisture content of seeds (Priestley et al., 1985), and, in plants subjected to episodic droughting, increased levels of malon-dialdehyde occur (Price Hendry, 1987). 

Lipid peroxidation is probably the most studied oxidative process in biological systems. At present, Medline cites about 30,000 publications on lipid peroxidation, but the total number of studies must be much more because Medline does not include publications before 1970. Most of the earlier studies are in vitro studies, in which lipid peroxidation is carried out in lipid suspensions, cellular organelles (mitochondria and microsomes), or cells and initiated by simple chemical free radical-produced systems (the Fenton reaction, ferrous ions + ascorbate, carbon tetrachloride, etc). In these in vitro experiments reaction products (mainly, malon-dialdehyde (MDA), lipid hydroperoxides, and diene conjugates) were analyzed by physicochemical methods (optical spectroscopy and later on, HPLC and EPR spectroscopies). These studies gave the important information concerning the mechanism of lipid peroxidation, the structures of reaction products, etc. 

Simultaneous decrease in the content of diene conjugates and increase in the content of Schiff bases evidence the quick shift of pro-/antioxidant equilibrium, generation of reactive radicals, and damage of cell membranes in EAC cells, because Schiff bases, generated as a consequence of interaction of malonic dialdehyde with aminogroups of phospholipids and proteins, are highly reactive compounds causing polycondensation of molecules and formation of intermolecular bonds. 

Reaction of methylene derivatives of malonic dialdehyde 82 with nitriles 27 leads to 6-unsubstituted aminopyrans 83 (87CCC2687, 01T5591) (Scheme 23). 

The simplest 1,3-dicarbonyl precursor for the synthesis of 4//-pyrans is malonic dialdehyde. Because of its instability128 it must be generated in situ by hydration of propargyl aldehyde62,127 or 3-chloroacrolein,129,130 or by hydrolysis of 3-ethoxy-l,l,3-triethoxypropane.127 It underwent62,127,131 cycli-zation with a simple aldehyde, giving 3,5-diformyl-4//-pyrans 85a-d (40 to 90°7o). Lower yields were achieved in the preparation of 85e,f. 

Sorbic Acid and Sorbates. In addition to the correction of the volatile acidity for sorbic acid already mentioned, both sorbic acid and sorbates must be determined directly. The colorimetric procedure of Jaulmes et al. (10) is appropriate oxidation of sorbic acid to malonic dialdehyde and a red color developed by reaction with 2-thiobarbituric acid (4). 

Generally, there is no limitation in the 1,3-dicarbonyl compound used. However, several types of these substances are not stable, such as malone dialdehydes or formyl acetic acid. In such cases, l,l,l-trichloro-4-oxo-butanone 96 is an appropriate substitute, since the trichloromethylcarbonyl moiety can easily be transformed into a carboxylic acid ester after the reaction by treatment with an alcohol and a... 

The choice of an aromatic amine is a good one as the NH2 group reacts well with carbonyl compounds and it activates tire ortho position to electrophilic attack. However, the dialdehyde is malonic dialdehyde, a compound that does not exist, so some alternative must be found. If the quinoline is substituted in the 2- and 4-positions this approach looks better. 

The scope of this method is limited by the fact that at least one of the two substituents R and R must be an aryl residue this group may in fact be responsible for the relatively smooth elimination of water to form 11. Thus dibenzoylmethane (10a) and benzoylacetone (10b) give good yields of the salts 12a and 12b, which can be isolated as the perchlorates acetylacetone (10c)7 and malonic dialdehyde (10d),8 on the other hand, do not undergo this reaction. 

Some of these aminothiones react further with excess amine thus the cis isomer of the malonic dialdehyde dianil (107) has been obtained by the reaction of the 4-phenyl-1,2-dithiolium salt (105) with two moles of aniline.24... 

The major aldehyde products of lipid peroxidation are malon-dialdehyde and 4-hydroxynonenal (Table 1, Fig. 4). Malondi-aldehyde can react with DNA to generate adducts at the bases A, C, and G. The mutagenic adduct MIG (pyrimido(l,2-a)purin-10(3H)one) has been detected at levels as high as 1 adduct per 10 nucleosides in human tissues. MIG is a reactive electrophile that can undergo further modification, leading to crosslinking of an adducted DNA strand to the opposite strand, or to some protein (22). Exocyclic etheno adducts can also arise from lipid peroxidation, possibly by reaction of an epoxide of 4-hydroxynonenal with A, C, or G in DNA. 

Several attempts of FruA-catalyzed DHAP additions to simple aliphatic dialdehydes like glyoxal or glutaric dialdehyde have been reported in the literature, but in no case had a product been isolated and characterized [72,85]. Malonic dialdehyde cannot be used because it tends to enolize under protic conditions and engages in polycondensations. Our own extensive studies corroborate that enzymatic assays indicate a consumption of DHAP, but no defined products result according to t.Lc. or NMR analysis. Problematic also is the fact that aliphatic dialdehydes irreversibly destroy enzymatic activity by protein cross-linking [86,87]. 

Malondialdehyde precursor Malonic dialdehyde tetraethyl acetal. 

Protein sequence analysis Malonic dialdehyde tetraethylacetal. 

Nair, V. and Turner, G.A. (1984) The thiobarbituric acid test for lipid peroxidation structure of the adduct with malon-dialdehyde. Lipids 19 804-805. 

Valenzuela, A. (1991) The biological significance of malon-dialdehyde determination in the assessment of tissue oxidative stress. Life Sci. 48 301-309. 

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