Fatty Acids and Acylglycerols Nomenclature

Fatty acids are hydrocarbons of chain length two or greater with a carboxyl group at one end. Hydrocarbon chains are termed acyl lipids, and fatty acids occur most abundantly esterified to glycerol as tria-cylglycerols (Figure 1). Nomenclature for fatty acids has evolved from studies of food or organ sources of

Triacylglycerol

Figure 1 Stereochemical numbering of lipids derived from glycerol. R1, R2, and R3 refer to sn nomenclature.

Table 1 Fatty acids important in nutrition

Symbola

Systematic nameb

Common name

Melting point ( °C) Sources

Saturated fatty acids (SFAs)

n-Ethanoic n-Propanoic n-Butanoic n-Hexanoic n-Octanoic n-Decanoic n-Dodecanoic n-Tetradecanoic n-Hexadecanoic n-Octadecanoic n-Eicosanoic n-Docosanoic n-Tetracosanoic

Monounsaturated (monoenoic) fatty acids

10:1 n-1 cis-9-Decenoic

12:1 n-3 cis-9-Dodecenoic

14:1 n-5 cis-9-Tetradecenoic

16:1 n-7t trans-Hexadecenoic

16:1 n-7 cis-9-Hexadecenoic

18:1 n-9 cis-9-Octadecenoic

18:1 n-9t trans-9-Octadecenoic

18:1 n-7t trans-11-Octadecenoic

20:1 n-11 cis-9-Eicosaenoic

20:1 n-9 cis-11-Eicosaenoic

22:1 n-9 cis-13-Docosaenoic

Polyunsaturated (polyenoic) fatty acids

Dienoic

18:2 n-9 cis,cis-6,9-Octadecadienoic

18:2 n-6 cis,cis-9,12-Octadecadienoic

Trienoic 18:3 n-6 18:3 n-3 20:3 n-6 Tetra; penta; hexaenoic 20:4 n-6 20:5 n-3 22:4 n-6 22:5 n-6 22:6 n-3

All-cis-6,9,12-octadecatrienoic All-cis-9,12,15-octadecatrienoic All-cis-8,11,14-eicosatrienoic

All-cis-8,11,14-eicosatetraenoic All-cis-5,8,11,14,17-eicosapentaenoic All-cis-7,10,13,16-docosatetraenoic All-os-7,10,13,16,19-docosapentaenoic All-os-4,7,10,13,16,19-docosahexaenoic

Acetic 16.7

Propanoic -22.0

Caprylic 12.7

Capric 29.6

Lauric 42.2

Myristic 52.1

Palmitic 60.7

Stearic 69.6

Arachidic 75.4

Behenic 80.0

Lignoceric 84.2

Caproleic Lauroleic Myristoleic Palmitelaidic

Palmitoleic 1

Oleic 16

Elaidic 44

trans Vaccenic 44 Gadoleic

Gondoic 24

Erucic 24

Linoleic - 5

7-Linolenic a-Linolenic -11

Dihomogammalinolenic

Arachidonic -49.5

EPA, Timnodonic

Adrenic

DPA, Clupanodonic DHA

Many plants Rumen

Rumen and milk fat Milk fat

Milk fat, coconut Milk fat, coconut Coconut, palm kernel Milk fat, coconut Most common SFA in plants and animals Animal fat, cocoa butter Widespread minor Minor in seeds Minor in seeds

Milk fat Milk fat Milk fat HVOc

Most fats and oils Most fats and oils Ruminant fat, HVOc Ruminant fat Fish oils

Rapeseed, fish oils Rapeseed, mustard oil

Minor in animals Most plant oils

Evening primrose, borage oils Soybean and Canola oils

Meat Fish oils Brain Brain Fish aNumber of carbons:number of double bonds, location of first double bond from the methyl carbon. ^Geometric isomer-A positions of double bonds. cHVO, hydrogenated vegetable oil.

double bonds are 3 carbons apart, referred to as 'methylene interrupted,' as contrasted with conjugated double bonds (Figure 3).

Cis Trans

Figure 2 Structure of cis and trans double bonds.

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