Furan fatty acids

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Furanoid fatty acids (FFA of Engl. Furan fatty acids ), and F-acids mentioned are a group of fatty acids having a furan ring include. There is an unbranched carboxylic acid residue in one position of the furan ring , and an alkyl residue in another position. The natural furan fatty acids are also mono- or twofold methyl - substituted on the furan ring . They can be detected in a large number of plant and animal species.

Carboxyl-substituted F-acids are called urofuranic acids . Urofuran fatty acids are metabolic products of furan fatty acids, which can be detected, for example, in human urine (named).

general structure of furan fatty acids

The general structure of furan fatty acids
The most common methyl-substituted furan fatty acids
m n R.
2 8th CH 3
4th 8th H
4th 8th CH 3
2 10 CH 3
4th 10 H
4th 10 CH 3
4th 12 H
4th 12 CH 3

Occurrence

Furan fatty acids are mainly found in the liver fat of fish , crustaceans and horn corals . They are also found in the livers of cattle and rats , as well as in human blood ; either in free form or bound in triglycerides or esterified to cholesterol . In fish, the concentration of furan fatty acids in the liver is particularly high after periods of starvation .

Furan fatty acids can be detected in a large number of organisms and products such as butter or clarified butter . It is now assumed that this class of compounds is ubiquitous .

All occurrences of furan fatty acids in animals are based on the uptake and accumulation of furan fatty acids from plant components. The total content of furan fatty acids in human blood is around 50 ng / ml. A person excretes between 0.5 and 3 mg of urofuranic acids - the metabolic product of furanic acids - per day. Animals are not able to synthesize F-acids. Larger amounts of furan fatty acids are mainly produced by algae, but also by some plants and microorganisms. Fish and mammals use these as food and the furan fatty acids supplied in this way are incorporated into phospholipids and cholesterol esters .

Function and physiological effect

The metabolism of furan fatty acids to urofuranic acids in humans. In rats and cattle, instead of the methyl group on the furan ring, the terminal methyl group of the alkyl chain is oxidized.

Furan fatty acids are reactive compounds. By photo-oxidation , auto-oxidation or catalyzed by lipoxygenase -1 they are easily oxidizable. When exposed to light, furan fatty acids react with singlet oxygen to form the aromatic substance 3-methyl-2,4-nonanedione (MND), which has a hay-like odor and is contained in green tea , for example .

Furan fatty acids act as free radical scavengers. In the example, two hydroxyl radicals are trapped, with a dioxoenic fatty acid being formed.

Furan fatty acids are very effective free radical scavengers . Here Dioxoen-fatty acids are formed which are very unstable and even with thiols , such as cysteine or glutathione , thioether form. As potent antioxidants, they specifically trap hydroxyl radicals . It is therefore believed that this is their main function in various biological systems. They also inhibit the hemolysis of the erythrocytes (dissolution of the red blood cells) induced by singlet oxygen .

The biosynthesis of furan fatty acids

Plants and algae form furan fatty acids by means of biosynthesis from polyunsaturated fatty acids (PUFA, from English polyunsaturated fatty acids ). These obviously serve to protect against free radicals that are generated in these organisms by the action of sunlight.

Occasionally, it is speculated that the health-promoting properties originally attributed to omega-3 fatty acids may not be due to them, but to the furan fatty acids also contained in fish. A clinical study shows that when isolated omega-3 fatty acids, such as eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA), are administered to patients who have already had a myocardial infarction , there is no significant difference in cardiovascular effects compared to a placebo .

The exact pathological effects of furan fatty acids have not yet been clarified in detail and are the subject of current research projects. In addition to the antioxidant effect, one also suspects antitumoral (against malignant tumors ) and antithrombotic (against thrombosis ) effects. In 2002, xenohormonal properties were observed for the two furan fatty acids 9, (12) -oxy-10,13-dihydroxystearic acid and 10, (13) -oxy-9,12-dihydroxystearic acid. In in vitro tests on MCF-7 cells (breast cancer cells with estrogen receptors ), mitogenic properties and an influence on oestrus were found. In the latter, the transition to metestrus was initiated. In vivo , a reduction in willingness to mate was observed in female pet rats after the administration of furan fatty acids. However, neither an estrogenic nor an anti-estrogenic activity was detected. No negative effects on food intake, fertility, egg weight, egg shell thickness and other reproductive parameters were found in chickens after the targeted administration of furan fatty acids.

discovery

Furan fatty acids were first detected in 1966 by LJ Morris and colleagues as a component of an oil obtained from the seeds of Exocarpos cupressiformis (a plant from the order of the sandalwood-like ). Years later, other analytical methods were used to determine that the oil from Exocarpos cupressiformis does not contain the furan fatty acid 9,12-epoxyoctadeca-9,11-dienoic acid described by Morris, but that this only occurs during sample preparation through the oxidation of hydroxy fatty acids , during base-catalyzed transesterification for the type of Morrie and colleagues Argentationschromatographie has arisen. In 1974, furan fatty acids were identified for the first time by Robert L. Glass and colleagues in pike ( Esox lucius ) using gas chromatography and downstream mass spectroscopy (GC-MS).

further reading

Individual evidence

  1. ↑ S. Göckler: Metabolism and genetic toxicity of furan fatty acids, as well as their influence on cell membranes in vitro. Dissertation, University of Karlsruhe, 2009.
  2. ↑ DM Sand, H. Schlenk, H. Thoma, G. Spiteller: Catabolism of fish furan fatty acids to urofuran acids in the rat In: Biochim. Biophys. Acta 751, 1983, pp. 455-461 PMID 6849955 .
  3. ↑ H. Guth and W. Grosch: Furan fatty acids in butter and butter oil. In: Journal for food investigation and research A 194, 1992, pp. 360–362. doi: 10.1007 / BF01193220
  4. ↑ K. Hannemann et al: The common occurrence of furan fatty acids in plants. In: Lipids 24, 1989, pp. 296-298. doi: 10.1007 / BF02535166 PMID 2755307 .
  5. ↑ a b R. Pompizzi: Furan fatty acids as precursors of flavorings. Dissertation, ETH Zurich, 1999.
  6. ↑ CP Gorst-Allman et al .: Investigations of the origin of the furan fatty acids (F-acids). In: Lipids 23, 1988, pp. 1032-1036. doi: 10.1007 / BF02535648 PMID 3237002 .
  7. ↑ Gerhard Spiteller: Furan fatty acids . In: News from chemistry, technology and the laboratory . tape 35 , no. 12 , 1987, pp. 1240-1243 , doi : 10.1002 / nadc.19870351204 .
  8. ↑ a b c G. Spiteller: Furan fatty acids: Occurrence, synthesis, and reactions. Are furan fatty acids responsible for the cardioprotective effects of a fish diet? In: Lipids 40, 2005, pp. 755-771. doi: 10.1007 / s11745-005-1438-5 PMID 16296395 (Review).
  9. ↑ Simon Göckler: Metabolism and genetic toxicity of furan fatty acids, as well as their influence on cell membranes in vitro . Karlsruhe 2009, DNB  1013696247 , p. 11 , urn : nbn: de: swb: 90-106030 (dissertation, University of Karlsruhe).
  10. ^ A b c R. F. Boyer, D. Litts, J. Kostishak, RC Wijesundera, FD Gunstone: The action of lipoxygenase-1 on furan derivatives In: Chem. Phys. Lipids 25, 1979, pp. 237-246 PMID 119581 .
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  13. ↑ A. Batna and G. Spiteller: Oxidation of Furan Fatty Acids by Soybean Lipoxygenase-1 in the Presence of Linoleic Acid. In: Chem Phys Lipids. 70, 1994, pp. 179-185, 8033289.
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  15. ↑ Werner Grosch: The secret of the tea aroma. (PDF; 98 kB) (No longer available online.) In: teeverband.de. German Tea Institute, November 26, 2010, archived from the original on April 18, 2016 ; Retrieved February 20, 2017 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.teeverband.de
  16. ^ W. Grosch et al.: Textbook of the food chemistry publishing house Springer, 2007, ISBN 3-540-73201-2 , p. 987. Restricted preview in the Google book search
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  19. ^ Y. Okada et al: Hydroxyl radical scavenging activity of naturally occurring furan fatty acids. In: Biol Pharm Bull . 19, 1996, pp. 1607-1610, PMID 8996648 .
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  32. ↑ LJ Morris et al: A Unique Furanoid Fatty Acid from Exocarpus Seed Oil. In: Tetrahedron Lett. 7, 1966, pp. 4249-4253, doi: 10.1016 / S0040-4039 (00) 76045-X .
  33. ↑ FD Gunstone include: . Relative Enrichment of furan-containing Fatty Acids in the Liver of Cod Starving In: Chem Soc Chem Commun. 16, 1976, pp. 630-631. doi: 10.1039 / C3976000630B
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