Cyclopropane fatty acids (CPA) are a subgroup of

fatty acids In chemistry, particularly 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, f ...

that contain a

cyclopropane Cyclopropane is the cycloalkane with the molecular formula (CH2)3, consisting of three methylene groups (CH2) linked to each other to form a ring. The small size of the ring creates substantial ring strain in the structure. Cyclopropane itself ...

group. Although they are usually rare, the seed oil from

lychee Lychee (US: ; UK: ; ''Litchi chinensis''; ) is a Monotypic taxon, monotypic taxon and the sole member in the genus ''Litchi'' in the Sapindus, soapberry family, ''Sapindaceae''. It is a tropical tree native to Southeast and Southwest China (t ...

contains nearly 40% CPAs in the form of

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

Biosynthesis

CPAs are derived from unsaturated fatty acids by

cyclopropanation In organic chemistry, cyclopropanation refers to any chemical process which generates cyclopropane () rings. It is an important process in modern chemistry as many useful compounds bear this motif; for example pyrethroids and a number of quinolo ...

. 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 is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

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

Cyclopropene fatty acids

Cycloprop''e''ne fatty acids are even rarer than CPAs. The best-known examples are

malvalic acid Malvalic acid is a cyclopropene fatty acid found in baobab seed oil and cottonseed oil. The cyclopropene ring is thought to be one of the causes of abnormalities that develop in animals that ingest cottonseed oil. Refining processes, such as hyd ...

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 cyclop ...

. Sterculic acid as its triglyceride is present in sterculia oils and at low levels in kapok seed oil (~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. Cotton seed has a similar structure to other oi ...

(~1%), and in the seeds of the tree ''

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

'' (~65-78%). These acids are highly reactive but 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) 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 palmitoyl- ...

(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 waxy solid and its chemical formula is C17H35CO2H. Its name comes from the Greek word στέαρ "''stéar''", which means tallow. ...

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. In chemical terms, oleic acid is classified as a monounsaturated omega ...

. At least one review indicates that CPFA are

carcinogenic A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...

, co-carcinogenic, and have medical and other effects on animals;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. according to this review, "CPFA in food is dangerous to human health".

References

External links

* {{cite journal , doi = 10.1073/pnas.092152999 , pmid = 11997456 , pmc = 124547 , url = http://www.pnas.org/cgi/reprint/99/10/7172.pdf , title = Carbocyclic fatty acids in plants: Biochemical and molecular genetic characterization of cyclopropane fatty acid synthesis of Sterculia foetida , journal = Proceedings of the National Academy of Sciences , volume = 99 , issue = 10 , pages = 7172–7177 , year = 2002 , last1 = Bao , first1 = X. , last2 = Katz , first2 = S. , last3 = Pollard , first3 = M. , last4 = Ohlrogge , first4 = J. , bibcode = 2002PNAS...99.7172B , doi-access = free Fatty acids Cyclopropanes