Cyclopropane and cyclopropene acids



Some fatty acids contain either in the chain a cyclopropane ring (present mainly in bacterial lipids) or a cyclopropene ring (present in some seed oils),  or at the end of the chain a cyclopentene ring (seed oils).


Among cyclopropane acids, lactobacillic acid (11,12-methylene-octadecanoic acid) is found mainly in a gram-negative bacteria, Lactobacillus arabinosus, where it was discovered in 1951 (Hofman K et al., J Biol Chem 1951, 195, 473). but also in protozoa and in the seed oil of Byrsocarpus coccineus (Connaraceae) (Spencer GF et al., Lipids 1979, 14, 72). Its ring has some properties of a double bond and it may be disrupted by acids or halogens. In bacteria, lactobacillic acid is never accompanied by cyclopropene acids.


lactobacillic acid


Cyclopropane fatty acids (mainly lactobacillic acid) were detected for the first time in milk (about 0.1% of milk fat) and they were present only in milk samples from cows fed with forages containing maize silage (Marseglia A et al., Food Chem 2013, 140, 711). Their determination can be proposed as a quality parameter of milk or feed.
The seeds of Litchi chinensis (Sapindaceae) from Reunion Island were shown to contain unusual amounts (35-48%) of an isomer of lactobacillic acid : cis-9,10-methylene-octadecanoic acid (Gontier E et al., Biochem Soc Trans 2000, 28, 578). That cyclopropane fatty acid is  also present in longan (Euphoria longana) seed oil (Grondin I et al., Oléagineux Corps gras Lipides 1997, 4, 459). Furthermore, it was shown that this fatty acid was preferentially located at the sn-2 position of the triglyceride molecules.

The 2-octylcyclopropane-1-carboxylic acid or olibanic acid is a cyclopropane acid which was found to be present (in cis and trans forms) in frankincense, they have a true olibanum smell (Cerutti-Delasalle C et al., Angew Chem Int 2016, 55, 13719). These cyclopropyl-derived acids provide the very characteristic old churchlike endnote of the frankincense odor.


cis and trans-olibanic acid


Another cyclopropane fatty acid (9,10-methylene-hexadecanoic acid) was shown to be present in phospholipids of heart and liver mitochondria (Sakurada K et al., Biochim Biophys Acta 1999, 1437, 214). Its amount in bovine heart (about 4% of all fatty acids) is much greater than that in other tissues (less than 0.3%). The origin and the physiological role of these compounds remain unclear. Cyclopropane fatty acids have been also identified in human adipose tissue and serum (Sledzinski T et al., Lipids 2013, 48, 839). These compounds are stored in triacylglycerols but their origin remains unknown.


A novel brominated cyclopropyl fatty acid, majusculoic acid, with a 16-carbon chain has been reported in a cyanobacteria Lyngbya majuscula and was shown to exhibit antifungal activity against Candida albicans (MacMillan JB et al., J Nat Prod 2005, 68, 604).


majusculoic acid


Two unsaturated cyclopropyl C28 fatty acids (named amphimic acids), 10,11-methylene-28:2(5Z,9E) and 10,11-methylene-28:3(5Z,9E,21Z) were isolated from an Australian sponge Amphimedon sp., and were shown to be DNA topoisomerase inhibitors (Nemoto T et al., Tetrahedron Lett, 1997, 38, 5667; Tetrahedron, 1997, 53, 16699).


Cyclopropene acids are found in Malvales seed oils (Sterculiaceae, Gnetaceae, Bombacaceae, Tiliaceae, Malvalaceae and Sapindaceae) and Baobab, Kapok and Mowrah seed oils which are used as human food in Madagascar. They can reduce the commercial value of cotton (Malvales, Gossypium) seed oil in interfering with animal fatty acid metabolism (desaturation of stearic acid). Such toxic acids are deactivated or removed by normal industrial treatments. The biological effects of these molecules have been reviewed by Andrianaivo-Rafehivola AA et al. (Oleagineux 1994, 49, 177).
Compounds containing cyclopropenoid ring are associated with several biological properties, such a : insecticide, antifungal, antibiotic, antiviral, hormonal, carcinogenic or antitumoral activities and enzyme inhibitor (Salaun J, Top Curr Chem 2000, 207,1).

The 9,10-methylene octadec-9-enoic acid was discovered by Nunn (1952) in Sterculia foetida oil. It was named sterculic acid by Schlenk et al. (J Am Chem Soc 1952,72, 500). An homologue molecule, 8,9-methylene heptadec-8-enoic acid, was discovered in 1957 by Mac Farlane (Nature 1957, 179, 830) in Malva verticillata seed oil and named malvalic acid. Cotton oil (Gossypium hirsutum) was the first oil, used for human consumption, where cyclopropenic acids were shown to be present (Coleman EC et al. 1972) by the Halphen test (J Pharm 1897, 390). Sterculic acid was shown to be an inhibitor of the D9-desaturase which converts stearic acid into oleic acid, altering membrane permeability and inhibiting cellular reproduction (Dewick PM, Medicinal natural products, J Wiley and Sons, NY, 2001).

Both cyclopropenic acids are present in Malvales in various proportions. In Sterculiaceae, malvalic acid is present in the range 3-26% and sterculic acid in the range 5-54%, in Malvaceae O.5-5% and 0.3-7%, in Gnetaceae 13-39% and 13-28%, and in Bombacaceae 2-20% and 1-46%, respectively. 


cyclopropene acids


The Sterculia striata seeds, known as “chicha” nut in Brazil, are consumed by man and their oil was shown to contain about 4% of malvalic acid and 11% of sterculic acid (Aued-Pimentel S et al., J Chromatogr A 2004, 1054, 235). These levels may thus compromised the use of these nuts due to possible health implications caused by cyclopropenoid acid ingestion.
A review summarized the occurrence of cyclopropene acids in numerous plant families (Christie WW, in “Topics in Lipid chemistry”, vol 1, pp1-50, Logos Press Ltd 1970). This review may be completed with that of Vickery JR (JAOCS 1980, 57, 87).



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