Fatty acids

Synonym or sub-name for monovalent, aliphatic carboxylic acids (monocarboxylic acids), which in nature are either ester-like bound to glycerol or to high-molecular alcohols. Fatty acids are often given trivial names that relate to their natural occurrence, such as acetic acid, butyric acid or palmitic acid.

Fatty acids are organic compounds that consist of a hydrocarbon chain of varying lengths, usually unbranched, and a carboxyl group (-COOH). They occur in nature in great variety, for example in seed oils, fats and waxes. They are also involved in the formation of other natural substances such as phospholipids.

A distinction is made between saturated (no double formation) and unsaturated fatty acids (C=C), short- or long-chain fatty acids, branched (branched carboxylic acids are not always counted as fatty acids; they are found in some essential oils) or unbranched fatty acids.

Natural fatty acids: Many fatty acids occur naturally in plant and animal organisms, where they are usually not present as free acids but as esters or salts. Natural fatty acids usually consist of an even number of carbon atoms and are unbranched. The carbon chain must be at least 4 carbon atoms long, making butyric acid the simplest natural fatty acid.

Unsaturated fatty acids: Fatty acids with double bonds are called unsaturated fatty acids. If there are several double bonds, these are usually separated from each other by a CH2 group (-C=C-CH2-C=C-). Monounsaturated fatty acids are called monoenoic acids, diunsaturated fatty acids are called dienoic acids, trisaturated fatty acids are called trienoic acids and polyunsaturated fatty acids are called polyenoic acids.

Omega fatty acids: Unsaturated fatty acids are classified according to the position of their double bonds. The carbon atom that carries the carboxyl group is called the omega carbon atom. From here, all other atoms are numbered consecutively. E.g. omega-3 fatty acids, omega-6 fatty acids, omega-9 fatty acids.

Essential fatty acids (vitamin F): Essential fatty acids are polyunsaturated fatty acids that the body cannot synthesize itself. Of particular importance are the omega-6 fatty acids as components of vegetable oils, as well as the omega-3 fatty acids found in cold-water fish (herring, salmon) and the fish oils produced from them.

Examples of saturated fatty acids and their natural occurrence:

• Formic acid (methanoic acid, HCOOH; widespread)
• Acetic acid (ethanoic acid, CH3COOH; vinegar, through oxidation of ethanol)
• Propionic acid (C2H5COOH, produced during methane fermentation)
• Butyric acid (C3H7COOH; milk fat, sweat)
• Valeric acid (pentanoic acid, C4H9COOH; valerian root, wood vinegar)
• Caproic acid (hexanoic acid, C5H11COOH; milk fat, produced during butyric acid fermentation)
• Caprylic acid (octanoic acid, C7H15COOH; milk and coconut fat)
• Pelargonic acid (nonanoic acid, C8H17COOH; essential oil of Pelargonium roseum, cheese, wine)
• Capric acid (decanoic acid, C9H19COOH; animal and vegetable fats)
• Lauric acid (dodecanoic acid, C11H23COOH; milk fat, vegetable fats)
• Myristic acid (tetradecanoic acid, C13H27COOH; milk fat, fish oil, animal and vegetable fats)
• Palmitic acid (hexadecanoic acid, C15H31COOH; palmitic acid and stearic acid, as glycerol esters, are the main components of all animal and vegetable fats).
• Margaric acid (heptadecanoic acid, C16H33COOH; animal and vegetable fats)
• Stearic acid (octadecanoic acid, C17H35COOH; frequently occurring animal and vegetable fats, used as a food additive (E 570)).
• Arachidic acid (eicosanoic acid, C19H39COOH; in small quantities in plant seeds and animal fats)
• Behenic acid (docosanoic acid, C21H43COOH; in small amounts in plant seeds and animal fats, pathologically occurring in the organism in Gaucher's disease)
• Lignoceric acid (tetracosanoic acid, C23H47COOH; plant fats, component of sphingomyelins)
• Cerotic acid (hexacosanoic acid, C25H51COOH; beeswax, carnauba wax, montan wax)

Examples of monounsaturated fatty acids:

• Undecylenic acid (C10H19COOH)
• Palmitoleic acid (C15H29COOH; milk fat, animal depot fat, fish oil, vegetable fat)
• Oleic acid (C17H33COOH; in almost all natural fats)
• Elaidic acid (C17H33COOH; in animal fats)
• Eicosenoic acid (C19H37COOH; in rapeseed oil)

Examples of polyunsaturated fatty acids:

• Linoleic acid (C17H31COOH; vegetable oils, especially safflower oil)
• Linolenic acid (C17H29COOH; various vegetable oils, especially linseed oil; the linoleic acid isomer with the double bonds in positions 9, 12 and 15 is called alpha-linolenic acid, the isomer with the double bonds in positions 6, 9 and 12 is called gamma-linolenic acid).
• Arachidonic acid (C19H31COOH; animal fats, fish oil)
• Cervonic acid (C21H31COOH; fish oil)

Fatty acids are mainly used in the food industry as raw materials for various emulsifiers. Fatty acids are also used as carriers, release agents or coating agents. Fatty acids are generally authorized in the EU as food additives under the collective designation E 570 without a maximum quantity restriction (quantum satis) for foodstuffs.

Soaps: Soaps are sodium or potassium salts of the higher fatty acids. They are used as surfactants.

1. Bährle-Rapp (2012) Springer Lexicon Cosmetics and Personal Care. 4th revised and extended edition. Springer Publishing House GmbH S 212-213
2. Burger A et al (1993) Hunnius Pharmaceutical Dictionary 7th Edition Walter de Gruyter Berlin-New York S 539-544