Polyunsaturated fatty oxygen activation

The stimulus for the recent surge of activity in this previously dormant area of organic chemistry can be traced to the prostaglandin connection . That is to the discovery that saturated bicyclic peroxides are key intermediates in the biosynthesis of prostaglandins and other physiologically active substances by the enzymatic oxygenation of polyunsaturated fatty acids. 

The E vitamins consist of eight naturally occurring tocopherols, of which a-tocopherol is the most active (Figure 28.28). The primary function of vitamin E is as an antioxidant in prevention of the nonenzymic oxidation of cell components (for example, polyunsaturated fatty acids) by molec ular oxygen and free radicals. 

Precautions should be taken to prevent oxidation during lipid analysis. Polyunsaturated fatty acids in lipid samples are easily attacked by active oxygen species (e.g., free radicals), exacerbated by the presence of strong light and metal ions. Therefore, it is arule of thumb while working with lipids that samples should be handled in a way that minimizes contact with air, light, and metals. To accomplish this, handle samples in glass vessels, use Teflon-lined or coated materials, and maintain the samples... 

Direct Measurements—UVNIS Techniques. The conjugated diene (CD) formed among the polyene hydroperoxide products that are formed as a result of oxidation of polyunsaturated fatty acids (PUFAs) have a UV absorbance that can be monitored to follow the progress of the oxidation. The effect of antioxidants on the suppressed rate of product formation can be followed with time. For example, conjugated dienes from oxidation of linoleate lipid molecules absorb at 234 nm and can be monitored directly , or else after HPLC separation (via normal phase or reverse phase j of the individual isomers. In order to use these findings to calculate the antioxidant activity of phenols and relate it to oxygen uptake studies (equations 7 and 14), one also has to make a correction to account for loss of absorbance due to loss (from decomposition) of hydroperoxides (equation 22) . 

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