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THE FABULOUS DESTINY OF FATTY ACIDS
NOMENCLATURE OF FATTY ACIDS
Lipids are a group of naturally occurring simple to complex molecules which are
soluble in organic solvents. Within the dairy cow, especially cholesterol and lipids such
as triacylglycerols (TAG) and phospholipids (PL) are of particular interest.
Phospholipids are major components of cellular membranes, and are a source of fatty
acids (FA) for the synthesis of a variety of effector molecules such as the eicosanoids, a
group of compounds that includes prostaglandins, thromboxanes and leukotrienes
(Wathes et al., 2007). Triacylglycerols serve as the most important energy storage in the
animal whereas cholesterol is another component of the cellular membrane and is a
main precursor for the synthesis of steroid hormones (Mattos et al., 2000).
The main compound of lipids are FA that mainly exhibit their function through
the specific length of the hydrogenated acyl chain (2 up to 30), the number of double
bonds in the chain, and the type of isomers formed by each double bond (Semma, 2002;
Wathes et al., 2007). Fatty acids containing double bonds in the acyl chain are referred
to as unsaturated fatty acids (UFA) in contrast with saturated FA (SFA). A FA containing
one double bond is called a mono-unsaturated FA (MUFA) whereas a FA containing
more than one double bond is called a poly-unsaturated FA (PUFA; Semma, 2002;
Wathes et al., 2007). Often, FA are also classified according to their chain length into
short-chain (16 carbon atoms, LCFA; Chilliard et al., 2000).
According to their specific structure, FA have common and systemic names
(Table 2; Calder and Yaqoob, 2009). As a shorthand nomenclature, the official
International Union of Pure and Applied Chemistry and Molecular Biology (IUPAC-
IUBMB) nomenclature for FA is commonly used where the carbon length of the FA chain
is indicated by the number before the colon, and the number of the double bond is
indicated by the number after the colon (Fahy et al., 2005). For example, all FA with 18
carbon atoms in the acyl chain and 2 or 3 double bonds are classified as 18:2 and 18:3,
respectively. The position of the double bond relative to the methyl end is used to
classify the FA into different omega families. Members of the omega-6 (e.g. 18:2n-6;
linoleic acid; LA) and omega-3 (e.g. 18:3n-3; linolenic acid; LNA) family have the first
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