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Food Lipids: Chemistry, Nutrition, and Biotechnology

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Table 7 Short Abbreviations for Some Common Fatty Acids<br />

AC<br />

Ad<br />

An<br />

B<br />

Be<br />

D<br />

E<br />

El<br />

G<br />

H<br />

L<br />

La<br />

Lg<br />

Source: Ref. 31.<br />

Acetic<br />

Arachidic<br />

Arachidonic<br />

Butyric<br />

Behenic<br />

Decanoic<br />

Erucic<br />

Elaidic<br />

Eicosenoic<br />

Hexanoic<br />

Linoleic<br />

Lauric<br />

Lignoceric<br />

Ln<br />

M<br />

N<br />

O<br />

Oc<br />

P<br />

Po<br />

R<br />

S<br />

St<br />

U<br />

V<br />

X<br />

Linolenic<br />

Myristic<br />

Nervonic<br />

Oleic<br />

Octanoic<br />

Palmitic<br />

Palmitoleic<br />

Ricinoleic<br />

Saturated (any)<br />

Stearic<br />

Unsaturated (any)<br />

Vaccenic<br />

Unknown<br />

To facilitate TAG descriptions, fatty acids are abbreviated using one or two<br />

letters (Table 7). The triacylglycerols can be named after the esterified fatty acids<br />

using shorth<strong>and</strong> nomenclature. For example, sn-POSt is shorth<strong>and</strong> description for<br />

the molecule 1-palmitoyl-2-oleoyl-3-stearoyl-sn-glycerol. If the sn- is omitted, the<br />

stereospecific positions of the fatty acids are unknown. POSt could be a mixture of<br />

sn-POSt, sn-StOP, sn-PStO, sn-OStP, sn-OPSt, or sn-StPO, in any proportion. An<br />

equal mixture of both stereoisomers (the racemate) is designated as rac. Thus, rac-<br />

OPP represents equal amounts of sn-OPP <strong>and</strong> sn-PPO. If only the sn-2 substituent<br />

is known with certainty in a TAG, the designation �- is used. For example, �-POSt<br />

is a mixture (unknown amounts) of sn-POSt <strong>and</strong> sn-StOP.<br />

TAGs are also sometimes described by means of the � nomenclature. For<br />

example, sn-18:0-18:2�6-16:0 represents 1-stearoyl-2-linoleoyl-3-palmitoyl-sn-glycerol.<br />

C. Sterols <strong>and</strong> Sterol Esters<br />

The steroid class of organic compounds includes sterols of importance in lipid chemistry.<br />

Although the term ‘‘sterol’’ is widely used, it has never been formally defined.<br />

The following working definition was proposed some years ago: ‘‘Any hydroxylated<br />

steroid that retains some or all of the carbon atoms of squalene in its side chain <strong>and</strong><br />

partitions nearly completely into the ether layer when it is shaken with equal volumes<br />

of ether <strong>and</strong> water’’ [32]. Thus, for this definition, sterols are a subset of steroids<br />

<strong>and</strong> exclude the steroid hormones <strong>and</strong> bile acids. The importance of bile acids <strong>and</strong><br />

their intimate origin from cholesterol makes this definition difficult. As well, nonhydroxylated<br />

structures such as cholestane, which retain the steroid structure, are<br />

commonly considered sterols.<br />

The sterols may be derived from plant (phytosterols) or animal (zoosterols)<br />

sources. They are widely distributed <strong>and</strong> are important in cell membranes. The predominant<br />

zoosterol is cholesterol. Although a few phytosterols predominate, the<br />

sterol composition of plants can be very complex. For example, as many as 65<br />

different sterols have been identified in corn (Zea mays) [33].<br />

Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.

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