Ozone reactions with fatty acids

The kinetics of these processes are tabulated in Table II, for exposure times of 10, 15 and 20 min. The ratio of malondialdehyde to ozone uptake is high at first (9%) and then declines. The kinetics of these ratios are different than those for ozone reactions with free fatty acids, but the ratio is of... 

Srisankar, E. V. and L. K. Patterson. 1979. Reactions of ozone with fatty acid monolayers a model system for disruption of lipid molecular assemblies by ozone. Arch. Environ. Health 34, 346-349. 

Tomlinson and Rich have also considered the reaction of ozone (at 1 ppm for 30 min) with lipid components of the leaves. They found that a change in the fatty acid composition as a result of ozone treatment was an increase in the saturated fatty acid content. 

Studies of the reaction of ozone with simplified lipid systems have shown that malonaldehyde can be produced by direct ozonolysis. The use of malonaldehyde assay as an index of lipid peroxidation is therefore invalid in ozone studies. Liposomes formed from egg lecithin and prepared in aqueous media were quite resistant to ozone, but the contribution of polyconcentric spheres to this resistance has not been fully assessed. However, the bilayer configuration, with the susceptible unsaturated fatty acids shielded from ozone by the hydrophilic areas of the molecule, may be resistant. In hexane, where the fatty acid moieties are exposed, ozone reacts stoichiometrically with the double bonds. The experiments with aqueous suspensions of phosphatidylcholine gave no evidence of the formation of lipid peroxides,nor did experiments with films of fatty acids exposed to ozone. ... 

There is another reason to suspect that the primary reaction of ozone in these localized regions of the envelope is not with the unsaturated fatty acids, but rather with other moieties or parameters of the membranes. The increased staining density of the membranes and the electron-dense accumulations in these regions probably represent components released from the membrane which, upon release, are available for reaction with osmium. 

Thomberry, T. and Abbatt, J.P.D. (2004) Heterogeneous reaction of ozone with liquid unsaturated fatty acids detailed kinetics and gas-phase product studies. Physical Chemistry Chemical Physics, 6, 84-93. 

Localization of double bonds in unknown compounds has frequently been determined by ozonolysis. Unsaturated fatty acids of biological membranes are susceptible to ozone attack, but there are some important differences from autoxidation reactions. These include the fact that malonaldehyde is produced from linoleate by ozonolysis (53) but not autoxidation and also that ozonolysis does not cause double bond conjugation as judged by absorption at 233 nm (52). Reactions with the polyunsaturated fatty acids produce several possibilities for toxic reactions direct disruption of membrane integrity and toxic reactions caused by fatty acid hydroperoxides, hydrogen peroxide, and malonaldehyde. 

Experiments in vitro are consistent with some of the chemical investigations. Enzymes are readily inactivated by ozone, and the inactivation can be traced to the more susceptible amino acid residues (Table XI). Reactions with unsaturated fatty acids have been examined, and the production of malonaldehyde and hydrogen peroxide has been detected (52-54). The lipid products have not been analyzed, and the toxicity of such products is yet to be determined. 

Several reports of the effects of ozone in vivo are presented in Table XII. It is impossible to decide whether the effects of ozone are primary reactions or the result of a series of reactions initiated by ozone. All results can be rationalized as enzyme inhibition of one sort or another. Effects on membrane structure are harder to observe, and in one case it was reported that the malonaldehyde which would be expected on fatty acid ozonolysis was only observed after symptoms were apparent (74). Results of electron microscope examination showed that the first observable damage was in the stroma of the chloroplasts (70). One can easily argue that earlier damage could not be detected by microscopic techniques. However, recent reports that the chloroplast polyribosomes are much more susceptible to degradation by ozone are important observations which are consistent with the microscopy experiments (76). Chloroplast polysomes are also more susceptible to sulfhydryl reagents than are cytoplasmic polysomes (77). This evidence indicates that ozone itself, or a toxic product from primary oxidation, can pass through the cytoplasm and have its effect in the chloroplast. 

By this method (Z)-monounsaturated fatty acids and esters could be obtained with an ( )-isomer content of less than 10% this stereoselectivity being however inferior to that of the commonly used acetylenic approach 55,56). However, the salt-free techniques used today in Wittig reactions allow (Z)-alkenoic acids to be synthesized with less than 2% of the ( )-isomers. Thus, Bestmann et al. prepared methyl and ethyl esters of (Z)-4,5,6,7,8,9,ll- and 13-alkenoic acids of different chain lengths 35,57 62), which served as intermediates in the synthesis of insect pheromones, both by reaction of co-alkoxycarbonyl-substituted alkyl-triphenyl-phosphonium salts with simple alkanals and of co-formylalkanoic esters with alkylidenephosphoranes. As the starting material for the synthesis of -substituted alkyl-phosphonium salts co-chloro- and -bromocarboxylic esters were used. The corresponding -substituted aldehydes can usually be obtained by ozone cleavage of suitable olefin derivatives or by oxidation of alkohols 57,58). 

Ozone The reactivity of ozone with unsaturated fatty acids has long been recognized, and indeed, the reaction has practical applications in localization of double bonds (181). As a damage reaction, atmospheric ozone (O3) [e.g., from pollution or sterilization processes (182)] rapidly adds across double bonds in nearly all organic molecules to form ozonides (trioxides), which then undergo a number of different subsequent reactions, not all of which produce free radicals. However, there remains some controversy over whether direct or indirect mechanisms dominate. 

Ozone preferentially reacts with the most unsaturated fatty acids present (187) arachidonic acid and higher PUFAs are particularly sensitive. T ranj -double bonds and fatty acids have been reported to react with ozone much more slowly than cis-double bonds (21), but this observation may be an artifact of measuring only initial ozonides. In fact, tran -fatty acids do react with ozone, but the initial ozonides decompose and rearrange more rapidly to generate peroxy-epoxide or peroxy-ozo-nide complexes and free acids (188). This is another example of how, as in lipid oxidation itself, downstream as well as initial products must be measured to obtain a full and accurate picture of reaction. 

Ozone exerts a toxic action by forming free radicals. The formation of these radicals can be accomplished by a reaction of ozone with SH-groups [18] or by a reaction of ozone with unsaturated fatty acids. It is assumed that ozone can cause a lipidic peroxidation under in vitro as well as in vivo conditions [19]. 

In analogy with this process, we have suggested (45a) that the trioxide formed from ozone addition to one of the double bonds in a polyunsaturated fatty acid can undergo the similar reaction, eq 33b, in which an allylie hydrogen atom is abstracted, Eq 33b... 

We have developed a novel catalytic ozonation process whereby unsaturated fatty acids are cleaved by the ozone and the resulting new chain-ends are reacted with an alcohol through an ester linkage. Although any alkaline catalyst is suitable for this process, we have used primarily CaCOa as it is stable to ozone, easily removed from the reaction mixture by filtration and it is readily available and economical. The ozonation process itself is relatively fast, simple, and unlike typical ozonation process, is a single-step process. All the reactions were run between 0°C and room temperature with no additional solvent. Furthermore, this process can be scaled-up to a continuous production. 

The infected cell, however, produces hydrogen peroxide as a defensive function. Apart form this, the electrophilic reaction of ozone can also take place with unsaturated fatty acids, as a membrane constituent of the vi-rally infected body cell, and injected peroxides into the cell. The enhanced quantity of peroxide in the cell affect the cell processes through two ways (1) the peroxides destroy the membranes of the human cell before reproduction cycle of the infected viruses has been completed or (2) produce a... 

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