Sterculic acid

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Structural formula
Structure of sterculic acid
General
Surname Sterculic acid
other names
  • 8- (2-octylcyclopropen-1-yl) octanoic acid
  • Sterculic acid
  • Sterculinic acid
  • Sterculic acid
Molecular formula C 19 H 34 O 2
Brief description

colorless oil

External identifiers / databases
CAS number 738-87-4
PubChem 12921
Wikidata Q2345401
properties
Molar mass 294.47 g mol −1
Physical state

solid to liquid

Melting point

18.2-18.3 ° C

safety instructions
GHS hazard labeling
no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

The cyclopropane fatty acid (engl. Sterculic acid ), scientific 8- (2-Octylcyclopropen-1-yl) octanoic acid, is a cyclic fatty acid which like the malvalic acid to the Cyclopropensäuren counts. It is an aliphatic monocarboxylic acid with a cyclopropene ring in the carbon chain. The names Sterculsäure and Sterculinsäure are common. The salts are called sterculates. The connection has been proven in many mallow plants (Malvaceae), which it serves as natural protection against predators and pathogens due to its properties that interfere with fat metabolism . A few other occurrences are known, but overall sterculic acid rarely occurs in the fatty acid spectrum of living things.

Name and history

Ripe fruits with seed pods of Sterculia foetida

In 1952 the compound was isolated from the seeds of the stink tree species Sterculia foetida and was given the (English) name sterculic acid based on it . The German translation of this term is inconsistent. The names cyclopropane fatty acid , Sterculsäure and Sterculinsäure occur with similar frequency, rare is called Sterculasäure .

When using the term sterculinic acid , care must be taken to ensure that it is not confused with another cyclopropenoid fatty acid, which bears the English name sterculynic acid and has been identified in the stink tree species Sterculia alata . It differs from sterculic acid primarily in that it has a triple bond at the end of the fatty acid chain facing away from the carboxy group .

Occurrence

Within the mallow family (Malvaceae) sterculic acid is widespread as a component of the glycerides of the seeds, leaves, stems and roots. It is usually associated with the chemically very similar malvalic acid . For example, sterculic acid is included too

But there are also some occurrences outside of the mallow family. In the seed oil of the legume counting Indigofera glabra is 10% cyclopropane fatty acid found. The tree-like liana Gnetum gnemon , which belongs to the naked samers and is used for human consumption, contains 13% sterculic acid in the fat content of its seeds (but with a relatively low total fat content of 4% in the dried seeds).

In addition, sterculic acid has been observed as a product of the deterioration process in nuts.

Biological importance

It is assumed that sterculic acid, like the other cyclopropenoid fatty acids , has a protective function for the plant against predators and pathogens, because the substance disrupts lipid metabolism by inhibiting the body's own processes that implement the insertion of a double bond into a fatty acid chain. This affects delta 5, delta 6, and delta 9 desaturation reactions. The consequences are diverse and result, among other things, in a reduction in growth and reproductive function; a feed content of 5% is fatal for rats . By inhibiting delta-9 desaturase , the body's own synthesis of oleic acid from stearic acid is prevented. This results in a changed body fat composition, which affects not only the storage fat, but also the lipid composition of the membranes . The melting point increases due to the increased proportion of saturated fatty acids. For example, sterculic acid in the feed of laying hens already leads to a noticeable discoloration of the eggs at a daily dose of 25 mg, especially during cool storage. The egg white takes on a pink color while the yolk appears apricot. The reason is an increased permeability of the membrane that separates the yolk from the egg white, which enables the protein conalbumin to pass from the egg white into the yolk. There, a pink complex forms with the iron present in the yolk, which in turn can diffuse back into the egg white .

According to tests on rainbow trout , sterculic acid is suspected of having carcinogenic and co-carcinogenic properties.

Sterculic acid levels in human food are viewed as hazardous to health, but can be removed by hydrogenation or by vigorous heating of the corresponding vegetable oils to 230 to 235 ° C during deodorization .

biosynthesis

Starting from oleic acid, a methylene group is added over the double bond by a cyclopropane fatty acid synthase . The methylene group is derived from S-adenosyl methionine . This creates dihydrosterculic acid , which contains a cyclopropane ring . It is assumed that a desaturase then converts the cyclopropane ring into a cyclopropene ring, which yields sterculic acid.

Extraction and presentation

This fatty acid can be obtained from vegetable oils that are rich in sterculic acid, such as the seed oil of Sterculia foetida . After the necessary cleavage of the triglycerides , the actual cleaning procedure takes place. The difficulties lie in the simultaneous presence of the chemically very similar malvalic acid , which only differs by one methylene group in chain length, and in the relative instability of the cyclopropene ring. The methods used are urea extractive crystallization , column chromatography and vacuum distillation .

In the laboratory, sterculic acid can be produced by a Simmons-Smith reaction from 9-octadecinic acid (stearolic acid) and diiodomethane (4% yield).

Synthesis of sterculic acid from stearolic acid.

Another synthesis approach with higher yield starts from 9-octadecinic acid and ethyl diazoacetate.

Analytics

Gas chromatography with mass spectrometry coupling (GC / MS) , for example, is suitable for detecting sterculic acid .

Sterculic acid shows the Halphen reaction due to the cyclopropene ring .

Individual evidence

  1. ^ A b J. Hernando, MP Matia, JL Novella, J. Alvarez-Builla: Synthesis of sterculic acid. In: ARKIVOC. 2002, Part (v), pp. 26–30, (PDF; 97 KB)
  2. ↑ a b c d e f F. D. Gunstone, JL Harwood, FB Padley: The Lipid Handbook. 2nd edition, Chapman & Hall, London 1994, ISBN 0-412-43320-6 , pp. 13, 51 f, 64 f, appendix p. 370.
  3. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
  4. ↑ a b N. E. Pawlowski, PM Loveland, RO Sinnhuber: Separation of methyl malvalate from methyl sterculate. In: J. Am. Oil Chem. Soc. 58 (6), 1981, pp. 692-94, doi : 10.1007 / BF02899451 .
  5. ↑ a b J. Salaün, MS Baird: Biologically Active Cyclo the propane and Cyclopropenes. In: Curr. Med. Chem. 2 (1), 1995, pp. 511-542.
  6. ↑ a b R. F. Keeler, AT Tu (ed.): Plant and Fungal Toxins. Handbook of Natural Toxins. Volume 1. Marcel Dekker Verlag, 1983, ISBN 0-8247-1893-3 , p. 271 f.
  7. ↑ W. Ternes, A. Täufel, L. Tunger, M. Zobel (eds.): Food Lexicon. 4th edition, Behr's Verlag, Hamburg 2005, ISBN 3-89947-165-2 , p. 911.
  8. ^ S. Krist, G. Buchbauer, C. Klausberger: Lexicon of vegetable fats and oils. Springer-Verlag, Vienna 2008, ISBN 978-3-211-75606-5 , p. 36.
  9. ↑ a b R. Hegnauer: Chemotaxonomy of plants. Volume 5. Birkhäuser Verlag, Basel 1969, ISBN 3-7643-0168-6 , p. 31 f.
  10. ^ R. Hegnauer, M. Hegnauer: Chemotaxonomie der Pflanzen. Volume XIb-2. Birkhäuser Verlag, Basel 2001, ISBN 3-7643-6269-3 , p. 280.
  11. ↑ W. Ternes, A. Täufel, L. Tunger, M. Zobel (eds.): Food Lexicon. 4th edition, Behr's Verlag, Hamburg 2005, ISBN 3-89947-165-2 , p. 672 f.
  12. ↑ a b L. O. Hanus, P. Goldshlag, VM Dembitsky: Identification of cyclopropyl fatty acids in walnut (Juglans regia L.) oil. In: Biomed. Pap. Med. Fac. Univ. Palacky. Olomouc. Czech. Repub. 152 (1), 2008, pp. 41-45, PMID 18795073
  13. ↑ RS Singhal, PR Kulkarni, DV Rege: Handbook of indices of food quality and authenticity. Woodhead Publishing Ltd, 1997, ISBN 1-85573-299-8 , p. 278.
  14. ↑ Entry EC  2.1.1.79 in the BRENDA enzyme database .
  15. ↑ a b X. Bao, S. Katz, M. Pollard, J. Ohlrogge: Carbocyclic fatty acids in plants: biochemical and molecular genetic characterization of cyclopropane fatty acid synthesis of Sterculia foetida. In: Proc. Natl. Acad. Sci. USA 99 (10), 2002, pp. 7172-7, PMID 11997456 .
  16. ^ J. Buddrus: Fundamentals of organic chemistry. 3rd edition, de Gruyter Verlag, 2003, ISBN 3-11-014683-5 , p. 165 f.