Monoenoic, monounsaturated

Monounsaturated (monoethenoid, monoenoic) acids, containing one double bond. 

Fatty acids of plant, animal, and microbial origin usually consist of an even number of carbon atoms in the straight chain. The number of carbon atoms of fatty adds in animals may vary from 2 to 36, whereas some microorganisms may contain 80 or more carbon atoms. Also, fatty adds of animal origin may have one to six ds double bonds, whereas those of higher plants rarely have more than three double bonds. Fatty adds also may be saturated, monounsaturated (monoenoic), or polyunsaturated (polyenoic) in nature. Some fatty acids may consist of branched chains, or they may have an oxygenated or cyclic structure. 

Escolar and oilfish contain a mixture of wax esters with different carbon-chain length, mainly C32, C34, C36, and C38, formed by combining different fatty acids and fatty alcohols. The dominant fatty acids in escolar and oilfish wax esters are the monounsaturated fatty acids (Table 1.3), namely oleic acid (18 1 oo9) and eicosenoic acid (20 loo9), while the dominant fatty alcohols are saturated and monoenoic fatty alcohols (Table 1.4), known as cetyl alcohol (16 0) and oleyl alcohol (18 1 9). PUFA, which are trace components in muscle wax esters, are commonly found in wax esters from roe, they include 20 4o)6, 20 5(b3, 22 5cd3 and 22 6 3. These differences could be due to the functional role in muscle for providing buoyancy, while that of roe is to store energy and key essential PUFA for fry development (Lee and Patton, 1989). 

The inclusion of HEAR oil in the diet resulted in a marked alteration of the fatty acid profile of both PC (Table XIV) and PE (Table XV). The concentration of saturated and monounsaturated fatty acids increased, while the concentration of 20 4 and C22 PUFA decreased. It should be noted, however, that the increase in monoenoic acids in cardiac PC and PE from rats fed HEAR oil could not be accounted for by an accumulation of 20 1 and 22 1. The concentration of 20 1 plus 22 1 in PC and PE was only 5 and 6.5%, respectively ... 

The anaerobic mechanism for monounsaturated fatty acid synthesis is by no means the most important. Indeed, it has only been observed in a limited number of bacteria - the Eubacteriales in particular. By far the most widespread pathway is by an oxidative mechanism, also discovered by Bloch s team, in which a double bond is introduced directly into the preformed saturated long chain fatty acid with O2 and a reduced compound (such as NADH) as cofactors. This pathway is almost universal and is used by bacteria, yeasts, algae, higher plants, protozoa and animals. Apparently, the two pathways are mutually exclusive because no organism has yet been discovered which contains aerobic and anaerobic mechanisms of desaturation. Most of the acids produced have a A9 double bond. Exceptions are A7 bonds in some algae, A5 and A10 monoenoic acids in Bacilli and a A6 acid (petroselenic) in some plants. 

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