Cyclopropane fatty acids (CPA) are a subgroup of

fatty acids In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...

that contain a cyclopropane group. Although they are usually rare, the seed oil from

lychee Lychee ( , ; ''Litchi chinensis''; ) is a monotypic taxon and the sole member in the genus ''Litchi'' in the soapberry family, Sapindaceae. There are three distinct subspecies of lychee. The most common is the Indochinese lychee found in So ...

contains nearly 40% CPAs in the form of

triglyceride A triglyceride (from '' tri-'' and '' glyceride''; also TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids. Triglycerides are the main constituents of body fat in humans and other vertebrates ...

Biosynthesis

CPAs are derived from unsaturated fatty acids by

cyclopropanation In organic chemistry, cyclopropanation refers to any chemical process which generates cyclopropane () Ring (chemistry), rings. It is an important process in modern chemistry as many useful compounds bear this motif; for example pyrethroid insectic ...

. The methylene donor is a methyl group on

S-adenosylmethionine ''S''-Adenosyl methionine (SAM), also known under the commercial names of SAMe, SAM-e, or AdoMet, is a common cosubstrate involved in methyl group transfers, transsulfuration, and aminopropylation. Although these anabolic reactions occur throug ...

(SAM). The conversion is catalyzed by cyclopropane-fatty-acyl-phospholipid synthase. The mechanism is proposed to involve transfer of a CH₃⁺ group from SAM to the

alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

, followed by deprotonation of the newly attached methyl group and ring closure.

Cyclopropene fatty acids

Cycloprop''e''ne fatty acids are even rarer molecules. The best-known examples are malvalic acid and

sterculic acid Sterculic acid is a cyclopropene fatty acid. It is found in various plants of the genus ''Sterculia'', including being the main component of ''Sterculia foetida'' seed oil. Biosynthesis The biosynthesis of sterculic acid begins with the cyclopro ...

. A triglyceride made of 3 sterculic acid molecules esterified with

glycerol Glycerol () is a simple triol compound. It is a colorless, odorless, sweet-tasting, viscous liquid. The glycerol backbone is found in lipids known as glycerides. It is also widely used as a sweetener in the food industry and as a humectant in pha ...

is present in ''

Sterculia foetida ''Sterculia foetida'' is a soft-wooded tree that can grow up to tall.Sterculia Foe ...

'' seed oil (in amounts greater than 60%) and at low levels in the seed oil of other species of

Malvaceae Malvaceae (), or the mallows, is a family of flowering plants estimated to contain 244 genera with 4225 known species. Well-known members of economic importance include Theobroma cacao, cacao, Cola (plant), cola, cotton, okra, Hibiscus sabdariffa, ...

(~12%),

cottonseed oil Cottonseed oil is cooking oil from the seeds of cotton plants of various species, mainly ''Gossypium hirsutum'' and ''Gossypium herbaceum'', that are grown for cotton fiber, animal feed, and oil. cottonseed, Cotton seed has a similar structure to ...

(~1%). The cyclopropene ring is destroyed during refining and hydrogenation of the oils. They have attracted interest because they reduce levels of the enzyme

stearoyl-CoA 9-desaturase Stearoyl-CoA desaturase (Δ-9-desaturase or SCD-1) is an endoplasmic reticulum enzyme that catalyzes the rate-limiting step in the formation of monounsaturated fatty acids (MUFAs), specifically oleate and palmitoleate from stearoyl-CoA and pal ...

(SCD), which catalyzes the biodesaturation of

stearic acid Stearic acid ( , ) is a saturated fatty acid with an 18-carbon chain. The IUPAC name is octadecanoic acid. It is a soft waxy solid with the formula . The triglyceride derived from three molecules of stearic acid is called stearin. Stearic acid ...

oleic acid Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish due to the presence of impurities. In chemical terms, oleic acid is cl ...

. At least one review indicates that these compounds are

carcinogen A carcinogen () is any agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and biologic agents such as viruse ...

ic.L. O. Hanus, P. Goldshlag, V. M. Dembitsky (2008). IDENTIFICATION OF CYCLOPROPYL FATTY ACIDS IN WALNUT (JUGLANS REGIA L.) OIL. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub. 2008, 152(1):41–45.

Biosynthesis

Cyclopropene fatty acids

Notes

References

Further reading