The ozonation of unsaturated fatty acids: aldehydes and hydrogen peroxide as products and possible mediators of ozone toxicity

Abstract

The products of the reactions of ozone with aqueous emulsions of unsaturated fatty acids and with liposomes made from phosphatidylcholine esters were characterized. Ozonolysis of emulsions of methyl oleate yields approximately 1 mol of hydrogen peroxide and 2 mol of aldehydes per mole of ozone used and fatty acid reacted. That is, the net equation that occurs is RCH = CHR' + O3 + H2O----RCHO + R'CHO + H2O2 . Ozonolysis of emulsions of oleic, linoleic, linolenic, and arachidonic acids gives 1 mol of hydrogen peroxide per mole of ozone used. Only very low yields (less than 5%) of reducible materials other than hydrogen peroxide are observed, suggesting that the yields of organic peroxidic materials, including Criegee ozonides and lipid hydroperoxides, are small. Ozonolysis of rat erythrocyte ghost membranes and rat bronchoalveolar lavage also gives significant yields (about 50%) of hydrogen peroxide based on the moles of ozone consumed. Reactions of ozone with bovine serum albumin, glutathione, and glucose do not produce hydrogen peroxide, implying that the hydrogen peroxide formed during the ozonation of biological materials arises almost exclusively from ozone/olefin reactions. Hydrogen peroxide and aldehydes are suggested to be important mediators of the modifications observed in both the lung and extrapulmonary tissues when ozone is inhaled.

Characterization by NMR of Ozonized methyl linoleate

“…Different kinds of oxygenated products are formed (hydroperoxides, ozonides and aldehydes) that probably are responsible for the biological activity of ozonized fatty acids. [7][8][9] The mechanism of this reaction is well known (Criegee mechanism, Figure 1), as well as the conditions necessary to enhance the preferential formation of any of these oxygenated compounds. 10,11 Of all the natural fatty acids, linoleic acid is one of the most widely distributed and is present in practically all lipids.…”

Impact of Recurrent Airway Obstruction (RAO) on Selected Antioxidants in Horses

“…Ozone in the upper and lower respiratory tract reacts with unsaturated fatty acids, proteins, and antioxidants, such as ascorbic acid and reduced glutathione (55). The effects of ozone on the respiratory system's response in the horse were researched by Deaton et al (56).…”

“…The concentration of AA, amino acid redox ratio (AARR), UA, GSH, GSSG and GRR did not differ significantly between the group of healthy horses and those suffering from RAO before ozone exposure, and the concentration did not change after animal exposure to the compound. A significant part of the administered ozone reacts with a variety of compounds, most likely with fats and proteins (24,55), which reduces its potentially harmful effects. It is possible that the doses and time points that authors selected were not optimal for assessing the effects of O 3 on antioxidants (57,58).…”

Detection of Aldehydes in Bronchoalveolar Lavage of Rats Exposed to Ozone

“…3 First, unsaturated fatty acids in lung lipids have long been considered to be a primary target for ozone (Pryor and Church, 1991;Pryor et al, 1991a;Goldstein and Balchum, 1967;Goldstein et al, 1969;Balchum et al, 1971;Mudd and Freeman, 1977). The epithelial cell-lining fluids (ELF) in the lung, including mucus and surfactant, contain from 20 to 40% unsaturated fatty acid-containing lipids (Harwood et al, 1975;Shelley et al, 1984;King, 1974;Sahu et al, 1976).…”

“…Aldehydes are of special interest, since the ozonation of unsaturated fatty acids in models of the ELF predicts that aldehydes are formed in yields of about 90% (along with hydrogen peroxide and some hydroxyhydroperoxides) and Criegee ozonides in about 10% yields (Pryor and Church, 1991;Pryor et al, 1991a;Pryor, 1994;Squadrito et al, 1992b). Aldehydes are also the most easily detected of the LOP formed at low levels in biologically relevant in vivo exposures.…”