α-Linolenic acid is an organic compound found in many common vegetable oils. In terms of its structure, it is named all-cis-9,12,15-octadecatrienoic acid. In physiological literature, it is given the name 18:3 (n−3).
α-Linolenic acid is a carboxylic acid with an 18-carbon chain and three cis double bonds. The first double bond is located at the third carbon from the end of the fatty acid chain, known as the n end. Thus, α-linolenic acid is a polyunsaturated n−3 (omega-3) fatty acid. It is an isomer of gamma-linolenic acid, a polyunsaturated n−6 (omega-6) fatty acid.
Alpha-linolenic acid was first isolated by Rollett as cited in J. W. McCutcheon's synthesis in 1942. and referred to in Green and Hilditch's 1930's survey.
Alpha-linolenic was first artificially synthesized in 1995 from C6 homologating agents. A Wittig reaction of the phosphonium salt of [(Z-Z)-nona-3,6-dien-1-yl]triphenylphosphonium bromide with methyl 9-oxononanoate, followed by saponification, completed the synthesis.
Seed oils are the richest sources of α-linolenic acid, notably those of rapeseed (canola), soybeans, walnuts, flaxseed (Linseed oil), perilla, chia, and hemp. α-Linolenic acid is also obtained from the thylakoid membranes of the green leaves of broadleaf plants (the membranes responsible for photosynthesis). Green vegetables, and therefore, animals that eat greens, are often a good source of α-linolenic acid.
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