Cyclopropane fatty acid

Cyclopropane fatty acids (CPA) are a subgroup of fatty acids that contain a cyclopropane group.[1] Although they are usually rare, the seed oil from lychee contains nearly 40% CPAs in the form of triglycerides.[2]

Examples of mycolic acids, a class of mono- and dicyclopropane fatty acids found in the cell wall of the bacterium Mycobacterium tuberculosis


Biosynthesis

CPAs are derived from unsaturated fatty acids by cyclopropanation. The methylene donor is a methyl group on S-adenosylmethionine (SAM). The conversion is catalyzed by cyclopropane-fatty-acyl-phospholipid synthase.[3] The mechanism is proposed to involve transfer of a CH3+ group from SAM to the alkene, followed by deprotonation of the newly attached methyl group and ring closure.[4]

Cyclopropene fatty acids
malvalic acid, a cyclopropene fatty acid

Cyclopropene fatty acids are even rarer than CPAs. The best-known examples are malvalic acid and sterculic acid. Sterculic acid as its triglyceride is present in sterculia oils and at low levels in the seed oil of species of Malvaceae[lower-alpha 1] (~12%), cottonseed oil (~1%), and in the seeds of the tree Sterculia foetida (~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 (SCD), which catalyzes the biodesaturation of stearic acid to oleic acid.[7]

At least one review indicates that CPFA are carcinogenic, co-carcinogenic, and have medical and other effects on animals;[8] according to this review, "CPFA in food is dangerous to human health".

Notes
  1. A number of species in several genera of the Malvaceae family are known as 'Kapok trees'. For example: Ceiba pentandra, Bombax ceiba and B. costatum are all widely and ambiguously called "the kapok".[5][6]

References
  1. "Natural alicyclic fatty acids, cyclopropane, cyclopropene, cyclopentene - structure, composition, analysis, biosynthesis". Archived from the original on 2014-12-17. Retrieved 2015-02-02.
  2. Gaydou, E. M.; Ralaimanarivo, A.; Bianchini, J. P. "Cyclopropanoic Fatty-Acids of Litchi (Litchi-Chinensis) Seed Oil - a Reinvestigation" J. Agr. Food Chem. 1993, vol. 41, pp. 886-890. doi:10.1021/jf00030a009
  3. Grogan DW, Cronan JE Jr: Cyclopropane ring formation in membrane lipids of bacteria" Microbiol Mol Biol Rev 1997, vol. 61, pp. 429-441. http://mmbr.asm.org/content/61/4/429.full.pdf+html
  4. Ludger A. Wessjohann and Wolfgang Brandt, Thies Thiemann "Biosynthesis and Metabolism of Cyclopropane Rings in Natural Compounds" Chem. Rev., 2003, volume 103, pp 1625–1648. doi:10.1021/cr0100188
  5. Bohannon, M. B.; Kleiman, R. (April 1978). "Cyclopropene fatty acids of selected seed oils from bombacaceae, malvaceae, and sterculiaceae". Lipids. 13 (4): 270–273. doi:10.1007/BF02533669. PMID 661511. S2CID 4017359.
  6. Yu, Xiao-Hong; Rawat, Richa; Shanklin, John (December 2011). "Characterization and analysis of the cotton cyclopropane fatty acid synthase family and their contribution to cyclopropane fatty acid synthesis". BMC Plant Biology. 11 (1): 97. doi:10.1186/1471-2229-11-97. PMC 3132707. PMID 21612656.
  7. Abraham, Samuel (1975). International encyclopedia of pharmacology and therapeutics: Pharmacology of lipid transport and atherosclerotic processes, Volume 1. Pergamon Press. p. 108. ISBN 9780080177625.
  8. 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.

Further reading
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