Structure of Linolenic Acid
Linolenic acid, strictly speaking, is not one acid but two. When the name is generically used, the one usually meant is alpha-linolenic acid (Figure 1). Found in many foods and food-based products, α-linolenic acid is an omega-3 fatty acid. The other linolenic acid is gamma- or γ-linolenic acid (Figure 2). It is an omega-6 fatty acid. Often fatty chains possess even numbers of skeletal carbons. The linolenic acids, with 18 carbon atoms, fit this description.
Other People Are Reading
-
Nomenclature
-
Using the Greek alphabet to identify each of the eighteen carbons, the alpha carbon is the carboxyl group (COOH) carbon, and the last or omega carbon is the methyl (CH₃) carbon at the other end. Since it has three double bonds in its chain, it is a polyunsaturated fatty acid. It is not a trans-fatty acid, since all three of its double bonds are cis-bonds. Its more descriptive name is cis, cis, cis - 9, 12, 15-octadecatrienoic acid.
Counting from the ω-carbon, α-linolenic acid has its first double bond located at the third carbon. It is thus called an omega-3 fatty acid.
By the same logic, the all cis γ-linolenic acid has its first double bond located at the sixth carbon from the ω-carbon, and so is an omega-6 fatty acid.
Sources of α-linolenic acid
-
While there are a number of rich sources of α-linolenic acid, among the more commercially viable ones are flaxseed, mustard seed, hemp seed, pumpkinseeds, rapeseed, green leafy vegetables and soybeans.
-
Sources of ω-linolenic acid
-
Humans require ω-linolenic acid; it is an essential fatty acid. Sources of ω-linolenic acid include evening primrose oil, black currant seed oil and borage oil. However, it is formed in the human body by converting the dietary substance, linoleic acid, which is found in many vegetable oils.
Diet and Health
-
It is currently believed that our diets should be richer in omega-6 fatty acids than in omega-3 acids. Multimedia frequently advertises the omega-3 acids. Although there are a plethora of health claims for both omega-6 and omega-3 fatty acids, there are also precautions to be noted, including possible drug interactions and for expectant mothers and very young children. Those using blood-thinners should also seek medical advice before beginning to supplement their diet.
Metabolism
-
The body metabolizes ω-linolenic acid, producing arachidonic acid. Arachidonic acid is involved in a number of enzyme-related processes. Arachidonic acid itself is plentiful in red meats, egg yolks and organ meats. The body controls how much arachidonic acid it produces. Too much of the foods mentioned is considered unhealthy.
Among many other substances, α-linolenic acid metabolizes into stearidonic acid.
-
References
Resources
- Photo Credit Fig. 1. α-linolenic acid; Edgar181: commons.wikimedia.org
