Anthraquinones

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Structural formula of anthraquinone

The anthraquinones are chemical compounds that are derived from the anthraquinone . They include natural substances of plant and animal origin as well as synthetic anthraquinone derivatives, which are used in particular as colorants . Some plant species are used medicinally because of their anthraquinone content .

Natural anthraquinones

Occurrence

In nature, anthraquinones are formed by fungi and seed plants and occur as colorants in some plant-sucking insects. Carminic acid is the pigment of the cochineal scale insect ( Dactylopius coccus ) and Lecanium ilicis , which sucks on Ilex species, contains kermesic acid .

Structures

In most anthraquinones, the anthracene backbone is substituted with one or more hydroxyl groups. Anthraquinones can be easily and reversibly reduced to anthrones and anthranols .

Anthrone derivatives have an activated methylene group at position 10 and can form C- glycosides at this point (e.g. aloin or barbaloin ). Most anthraquinones and anthrones, however, form O-glycosides. Often two anthraquinones or anthrones are connected via CC connections, for example in hypericin .

Some selected anthraquinones and their substitution patterns
Anthraquinone or anthraquinone derivative Basic structure R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8
Anthraquinone
The substance group of the anthraquinones with the blue marked basic structure of the 9,10-anthraquinone (R 1 to R 8 = H).
 −H −H −H −H −H −H −H −H
alizarin −OH −OH −H −H −H −H −H −H
Quinizarin −OH −H −H −OH −H −H −H −H
Chrysazine −OH −H −H −H −H −H −H −OH
Hystazarin −H −OH −OH −H −H −H −H −H
Purpurin −OH −OH −H −OH −H −H −H −H
Chrysophanic acid −OH −H −CH 3 −H −H −H −H −OH
Quinalizarin −OH −OH −H −H −OH −H −H −OH
Flavopurpurin −OH −OH −H −H −H −OH −H −H
Physcion −OH −H −CH 3 −H −H −OCH 3 −H −OH
Anthrarufin −OH −H −H −H −OH −H −H −H

biosynthesis

In most organisms, the anthraquinones are synthesized via the polyketide route and are therefore octaketides. Their biosynthesis starts thus with acetyl coenzyme A . These anthraquinones are produced by molds such as Aspergillus and Penicillium , by lichens , stand mushrooms , and higher plants such as the knotweed and buckthorn plants .

The biosynthesis occurs from an acetyl coenzyme A and seven malonyl-coenzyme A . These are combined to form an octaoxo acid, which is cyclized. The resulting anthrone body has a carboxyl group in position 2 and a methyl group in position 3. The former can be eliminated in sequence, the latter can be oxidized to a CH 2 OH or carboxy group. The anthrone can easily be oxidized to anthraquinone. Dimerization takes place via radicals that are formed by phenol oxidases or peroxidases.

Anthraquinones can be converted to xanthones by cleaving the middle B-ring and further reactions .

Anthraquinones are more rarely formed via the shikimic acid route . The biosynthesis proceeds via isochorismic acid , 2-succinylbenzoic acid, 1,4-naphthohydroquinone-2-carboxylic acid and 3-prenylnaphthohydroquinone-2-carboxylic acid. They share the biosynthetic pathway with the naphthoquinones and phylloquinones . One example is alizarin .

Analytics

The reliable qualitative and quantitative determination of the anthraquinones in different test materials succeeds after adequate sample preparation through the coupling of the HPLC with the mass spectrometry .

Medical use

Anthraquinones and anthraquinone derivatives are used as laxatives . Be used medically following anthrachinonhaltigen plants or plant parts: Senna leaves and fruits, alder bark , Cascararinde ( Rhamnus purshiana ), rhubarb root ( Rheum palmatum and Rheum officinale ), and Aloe ( Aloe capensis and Aloe barbadensis ). They prevent the resorption of sodium from the intestinal lumen and the associated water, so they have an antiresorptive effect. In addition, they can trigger the influx of fluid together with sodium, potassium , calcium and chloride ions into the intestine and thus have a secretagogue . These effects lead to a softer faeces and an increasing filling of the large intestine. By stretching the intestinal wall, the intestinal transit is accelerated and defecation is made easier. In the drug , the anthraquinones are present as glycosides. The sugars are only split off by bacteria in the large intestine, which is why the drugs only develop their effect here. The sugar-free aglycones are also known as emodins. They are reduced to the corresponding anthrones and anthranols by the intestinal bacteria. Only these substances are actually effective.

The anthraquinones and their derivatives are mainly excreted with the stool. Only around 5% is absorbed and excreted with the urine, which is darkened by them.

Anthraquinones are often administered in the form of teas, and finished medicinal products often contain dry extracts. Anthraquinones, like diphenylmethane derivatives, are only indicated in severe forms of constipation. An electrolyte shift in the serum was not observed with chronic ingestion.

Ecological importance

In plants, the anthraquinones probably function as a repellent against possible herbivores. Hypericin is a photoactive substance and acts as a repellent in Hypericum perforatum , likewise fagopyrin in buckwheat ( Fagopyrum esculentum ). Physcion and related anthraquinones are responsible for the striking colors in the fruiting bodies of mushrooms such as dermocybe .

Synthetic anthraquinones

The most important synthetic anthraquinones belong to the anthraquinone dyes or the corresponding intermediate dye products.

There are also some special applications such as B. the use of 2-ethylanthraquinone as a photoinitiator or as a catalyst in hydrogen peroxide production. Today, hydrogen peroxide is mainly produced using different variants of the anthraquinone process ( Riedl-Pfleiderer process ).

Individual evidence

  1. ^ Dieter Schlee: Ecological Biochemistry. 2nd Edition. Gustav Fischer Verlag, Jena 1992, ISBN 3-334-60393-8 , p. 355.
  2. ↑ a b c d e f Martin Luckner: Secondary Metabolism in Microorganisms, Plants and Animals. 3. Edition. VEB Gustav Fischer Verlag, Jena 1990, ISBN 3-334-00322-1 , pp. 176-178.
  3. ↑ Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 1: A-Cl. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1979, ISBN 3-440-04511-0 , pp. 222-223.
  4. ^ Martin Luckner: Secondary Metabolism in Microorganisms, Plants and Animals. 3. Edition. VEB Gustav Fischer Verlag, Jena 1990, ISBN 3-334-00322-1 , pp. 329-330.
  5. ↑ SY Wei, WX Yao, WY Ji, JQ Wei, SQ Peng: Qualitative and quantitative analysis of anthraquinones in rhubarbs by high performance liquid chromatography with diode array detector and mass spectrometry. In: Food Chem . 141 (3), 2013, pp. 1710-1715. PMID 23870882
  6. ^ S. Lee, SG Do, SY Kim, J. Kim, Y. Jin, CH Lee: Mass spectrometry-based metabolite profiling and antioxidant activity of Aloe vera (Aloe barbadensis Miller) in different growth stages. In: J Agric Food Chem . 60 (45), Nov 14, 2012, pp. 11222-11228. PMID 23050594
  7. ↑ ZW Zhu, J. Li, XM Gao, E. Amponsem, LY Kang, LM Hu, BL Zhang, YX Chang: Simultaneous determination of stilbenes, phenolic acids, flavonoids and anthraquinones in Radix polygoni multiflori by LC-MS / MS. In: J Pharm Biomed Anal . 62, 25 Mar 2012, pp. 162-166. PMID 22296653
  8. ↑ a b H. Kilbinger: Pharmaceuticals for influencing the functions of the stomach, small and large intestines - pharmacotherapy of gastrointestinal diseases. In: Klaus Aktories, Ulrich Förstermann , Franz Hofmann, Klaus Starke: General and special pharmacology and toxicology. 10th edition. Elsevier, Munich 2009, ISBN 978-3-437-42522-6 , pp. 571-573.
  9. ↑ AWMF Online: S2k guidelines for chronic constipation: definition, pathophysiology, diagnosis and therapy. ( Memento of the original from August 22, 2017 in the Internet Archive ) 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. (PDF; 588 kB), accessed on August 20, 2013. @1@ 2Template: Webachiv / IABot / www.awmf.org
  10. ^ Dieter Schlee: Ecological Biochemistry. 2nd Edition. Gustav Fischer Verlag, Jena 1992, ISBN 3-334-60393-8 , p. 309.
  11. ↑ Hans Beyer, Wolfgang Walter: Textbook of organic chemistry . 18th edition. S. Hirzel Verlag, Stuttgart 1978, ISBN 3-7776-0342-2 , p. 560 ff .
  12. ^ W. Arthur Green: Industrial Photoinitiators A Technical Guide . CRC Press, 2010, ISBN 978-1-4398-2746-8 , pp. 34 ( limited preview in Google Book search).
  13. ↑ Entry on hydrogen peroxide. In: Römpp Online . Georg Thieme Verlag, accessed on November 21, 2018.