Monoenoics

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

These are the esters of long-chain fatty acids and long-chain fatty alcohols. Usually, only the alcohols are saturated and monoenoic, whereas the fatty adds may be more highly unsaturated, as in most marine waxes. They are found in both animal and plant tissues as well as in some microorganisms. They are quite common in insects. They reserve energy in aquatic animals, aid in echolocation, and play a vital role in waterproofing. 

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. 

Tran. -isomers are much rarer than cis-isomers. Many different positional isomers of monoenoic acids may be present in a single, natural lipid and this is not a comprehensive list. Palmitoleic and oleic acids are quantitatively the commonest unsaturated fatty acids in most organisms. Odd-chain monoenoic acids are minor components of animal lipids but are more significant in some fish and bacterial lipids. 

S, saturated fatty acid M, monoenoic fatty acid D, dienoic fatty acid... 

The liquid phases of polar columns are usually the heat-stable polymers of ethyleneglycol and the dibasic acids, succinic or adipic (Table 12.13). Fatty acids are separated on the basis of both chain length and the degree of unsaturation and some columns are capable of resolving fatty acids with the same chain length but different numbers of double bonds (0-6). The saturated fatty acids show the shortest retention times followed by the monoenoic, dienoic, etc. (Figure 12.19). 

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 principal monoenoic acids, oleic (C18 1) and palmitoleic (C16 1), are derived from blood lipids but about 30% of these acids are produced by microsomal enzymes (in the endoplasmic reticulum) in the secretory cells by desaturation of stearic and palmitic acids, respectively ... 

Hay and Morrison (1970) identified the monoenoic positional and geometric isomers in milk fat and determined the amounts of each total acid class and percentage of trans isomers. The geometric and positional isomers of the monoenes are primarily the result of biohydrogenation of polyunsaturated fatty acids in the rumen. Stearate is also produced, and cis-9-18 l accounts for most of the monoenes. The several positional isomers in trans 16 1 and 18 1 are due to the positional isomerization of double bonds which accompanies elaidinization. 

Smith et al. (1978) have described a procedure for the GLC determination of cis and trans isomers of unsaturated fatty acids in butter after fractionation of the saturated, monoenoic, dienoic, and polyenoic fatty acid methyl esters by argentation TLC. Total trans acids were much higher, as measured by infrared spectrophotometry than by GLC, probably because some of the acids could have two or more of the trans bonds designated as isolated by infrared spectrophotometry. Enzymatic evaluation of methylene-interrupted cis, cis double bonds by lipoxidase resulted in lower values than those obtained by GLC. The authors mention that the lipoxidase method is difficult, requiring considerable skill, and suggest that their method is suitable for the determination of the principal fatty acids in complex food lipids such as bovine milk fat. 

Hay and Morrison (1971) later presented additional data on the fatty acid composition and structure of milk phosphatidylethanolamine and -choline. Additionally, phytanic acid was found only in the 1-position of the two phospholipids. The steric hindrance presented by the four methyl branches apparently prevents acylation at the 2-position. The fairly even distribution of monoenoic acids between the two positions is altered when the trans isomers are considered, as a marked asymmetry appears with 18 1 between the 1- and 2-positions of phosphatidylethanolamine, but not of phosphatidylcholine. Biologically, the trans isomers are apparently handled the same as the equivalent saturates because the latter have almost the same distribution. There are no appreciable differences in distribution of cis or trans positional isomers between positions 1 and 2 in either phospholipid. Another structural asymmetry observed is where cis, cis nonconjugated 18 2s are located mostly in the 2-position in both phospholipids. It appears that one or more trans double bonds in the 18 2s hinders the acylation of these acids to the 2-position. 

Hay, J. D, and Morrison, W. R. 1970. Isomeric monoenoic fatty acids in bovine milk fat. Biochim. Biophys. Acta 202, 237-243. 

A deficiency of very long-chain fatty acid oxidation in peroxisomes is apparently caused by a defective transporter of the ABC type (Chapter 8).55 The disease, X-linked adrenoleukodystrophy (ALD), has received considerable publicity because of attempts to treat it with "Lorenzo s oil," a mixture of triglycerides of oleic and the C22 monoenoic erucic acid. The hope has... 

In the anchovy, the total saturated fatty acids content in the reserve and structural lipid fractions is maximal in the autumn and minimal during the rest of the year. However, the polyenoic acids in these two fractions are maximal in winter, spring and summer, but minimal in autumn. During spring and summer, a substantial reduction is observed in the quantity of 16 0,18 1 and 22 6 in the triacyl-glycerols, perhaps because of transfer to sexual products in which they accumulate as stored energy (saturated and monoenoic acids) or as structural elements (polyenoic acids). They are of similar importance in this context in capelin, horse-mackerel, cod, Pacific saury, eelpout and trout (Jeffries, 1972 Dobrusin, 1978 Ackman, 1983 Henderson etaL, 1984). 

Suh et al. (1999) studied the isoforms of acyl carrier protein involved in seed-specific fatty acid synthesis in coriander seed, ft produces unusual monoenoic fatty acids which constitute over 80% of the total fatty acids of the seed oil. The initial step in the formation of these fatty acids is the desaturation of palmitoyl-ACP (acyl carrier protein) at the DELTA4 or DELTA6 positions to produce DELTA4-hexadecenoic acid (16 1DELTA4) or DELTA6-hexadecenoic acid (16 1DELTA6), respectively. 

These long-chain fatty acids have formulae similar to those described above but contain one or more double bonds. This group of fatty acids may be subdivided into monoenoic and polyenoic types. A general summary of the chemical nature of the unsaturated fatty acids follows. 

The commonly occurring unsaturated fatty acids contain a single double bond. There are a large number of possible monoenoic acids not only are... 

A list of the common monoenoic fatty acids is given in Table 1-2. 

The net result of these processes is that the fatty acids in the mammary gland, which originate from the dietary lipids, consist of substantial quantities of 16 0, 18 0 and oleic acid, small amounts of linoleic and linolenic acids, and limited quantities of other monoenoic and dienoic fatty acids such as llt-18 l and 9c, llt-18 2. 

There are about 200 minor monoenoic, dienoic and polyenoic fatty acids in milk fat ranging in chain length from C10 to C24, and consisting of both positional and cisltrans isomers. A number have considerable nutritional significance for example, eicosapentaenoic acid (20 5,0.09%) and docosahex-aenoic acid (22 6,0.01%) are present in the metabolic pathway of the n-3 fatty acids, while arachidonic acid (20 4, 0.14%) is part of the n-6 pathway. 

Laakso, P., Kallio, H. 1993. Triacylglycerols of winter butterfat containing configurational isomers of monoenoic fatty acyl residues. I. Disaturated monoenoic triacylglycerols.. / Am. Oil Chem. Soc., 70, 1161-1171. 

Pollard, M.R., Gunstone, F.D., James, A.T., Morris, L.J. 1980. Desaturation of positional and geometric isomers of monoenoic fatty acids by microsomal preparations from rat liver. Lipids. 15, 306-314. 

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