Unsaturated fatty acids, biological effects

Matsushita, S., Terao, J. 1980. Singlet oxygen-initiated photooxidation of unsaturated fatty acids and esters and inhibitory effect of tocopherols and (3-carotene. In Auto-oxidation in Food and Biological Systems (M.G. Simic, M. Karel, eds.), pp. 27 44, Plenum Press, New York. 

The natural fatty acid amides are mixtures of saturated fatty acid amides and unsaturated fatty acid amides. The present invention is based on the fact that the unsaturated fatty acid amides can be isolated very easily from a mixture of fatty acid amides by treating the fatty acid amides with urea or thiourea. The unsaturated fatty acid amides have more effective biological activity. 

Balchum et al. (1971) have provided evidence supporting the concept that the peroxidation or ozonization of unsaturated fatty acids in biological membranes is a primary mechanism of the deleterious effects of 03. The hypothesis is based on the tendency of 03 to react with the ethylene groups of unsaturated fatty acids, resulting in the formation of free radicals. The free radicals can, in the presence of molecular oxygen, cause peroxidation of unsaturated fatty acids. In support of this hypothesis is the evidence that after 03 exposure there was a relative decrease in unsaturated fatty acids as compared to saturated fatty acids, and the more unsaturated the fatty acid, the greater the loss. Furthermore, a deficiency of vitamin E increases the toxicity of 03 for the rat (Goldstein et al. 1970). 

We have previously mentioned that lipids make part of the membrane architecture, which has the typical bilayer arrangement due to the phospholipid supramo-lecular organization. This leads to biological consequences - the composition of fatty acid residues with saturated and unsaturated hydrocarbon chains is crucial to regulate membrane properties, maintaining the best balance for cellular functioning and also survival. Vesicle models made of phosphatidylcholines with saturated and unsaturated fatty acid residues are useful for studies of permeability and fluidity. Several studies have compared the effects of saturated, cis and trans unsaturated residues. An example is given in Fig. 6.4 for vesicles made up of different phospholipid compositions. 

Barnes, R. H., Lundberg, W. 0., Hanson, H. T., and Burr, G. 0.1943. Effect of certain dietary ingredients on the keeping quality of body fat. J. Biol. Chem. 149, 313. Barron, E. S. G., and Lyman, C. M. 1938. Studies on biological oxidations. X. Oxidation of unsaturated fatty acids with blood hemin and hemochromogens as catalysts. J. Biol. Chem. 123, 229. 

Prostaglandins are a group of compounds related to the unsaturated fatty acids. They were discovered in the 1930s, when it was found that human semen contained substances that could stimulate smooth muscle tissue, such as uterine muscle, to contract. On the assumption that these substances came from the prostate gland, they were named prostaglandins. We now know that prostaglandins are widely distributed in almost all human tissues, that they are biologically active in minute concentration, and that they have various effects on fat metabolism, heart rate, and blood pressure. 

Biological activity of vitamin E is related to antioxidant effects the most effective antioxidant in vivo) is a-tocopherol. In food lipids, the situation is more compHcated, because the antioxidant activity of tocopherols and tocotrienols depends on many factors. One important aspect is the amount and composition of unsaturated fatty acids. Under typical storage conditions, tocopherols are more effective antioxidants, for example, in animal fats (the main fatty acid is oleic acid) compared with vegetable oils that contain higher amounts of linoleic acid (e.g. soybean and sunflower oils). 

---