Lipid oxidation singlet oxygen

Ketones Aliphatic ketones formed by autoxidation of lipids also contribute to the flavor of oils and food products. For example, Guth and Grosch (13) identified l-octen-3-one as one of the odor-active compounds in reverted soybean oil. This compound was described as metallic and mushroom-like. The reaction pathway for the formation of l-octen-3-one from the linoleate-10-hydroperoxide via the p-scission route is illustrated in Figure 2. 10-Hydroperoxide of linoleate is not the usual hydroperoxide formed by autoxidation of linoleate however, it is one of the major hydroperoxides formed by the photosensitized oxidation (singlet oxygen reaction) of linoleate (14). 

Vile, G. R, and Tyrrell, R. M. 1995. UVA radiation-induced oxidative damage to lipids and proteins in vitro and in human skin fibroblasts is dependent on iron and singlet oxygen. Free Rad. Biol. Med. 18 721-22. 

If a large amount of the toxic substance is present, then the detoxication processes present are overwhelmed. Excess super oxide is produced, reduced GSH and NADPH are depleted, and hydroxyl radicals and singlet oxygen are formed. This is the condition known as oxidative stress (see also below this chapter). As well as causing lipid peroxidation, ROS will also cause DNA damage and damage to proteins. 

Stratton, S.P. and Liebler, D.C., Determination of singlet oxygen-specific versus radical-mediated lipid peroxidation in photosensitized oxidation of lipid bilayers effect of beta-carotene and alpha-tocopherol, Biochemistry, 36, 12911, 1997. 

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