Nomenclature
Derivation: The name for α-linolenic acid derives from Limun usitatissium, common name the flax plant, which is a known rich dietary source of the fatty acid.
Chemical name: cis-n-3,6,9-octadecatrienoic acid, cis-∆-9,12,15-octadecatrienoic acid; C18:3n-3
Formula: CH3(CH2CH=CH)3(CH2)7COOH
Proper name: α-linolenic acid
Abbreviations: ALA, ALNA, LNA
Structure and Classification
Alpha-linolenic acid is an 18 carbon polyunsaturated fatty acid (PUFA) with 3 double bonds. The first double bond is 3 carbon molecules from the omega (n-, ω-) (methyl) carbon, with subsequent double bonds methylene interrupted (on carbons 6 and 9). From the delta (∆-) end, the first double bond is 9 carbons from the carboxyl carbon with subsequent double bonds methylene interrupted (on carbons 12 and 15). The classification of ALA is therefore as an omega-3 or delta-9 fatty acid. The placement of the double bonds on the fatty acid chain are in the cis-configuration, and this gives the molecule a pronounced curvature due to the repulsion of the hydrogen molecules on the same side of the molecule. The structure of ALA is shown in figure 1.
Figure 1. The structure of the essential fatty acid α-linolenic acid. The placement of the double bonds with the cis-configuration produces a curvature in the molecule.
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