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Alkannin

Alkannin is a natural dye that is obtained from the extracts of the plant dyer's alkanet (Alkanna tinctoria) which is found in the Mediterranean region. The dye is used as a food coloring and in cosmetics; within the European E number schedule, it is numbered E103. It is used as a red-brown food additive in regions such as Australia. Alkannin is deep red in an acid and blue in an alkaline environment. The chemical structure as a naphthoquinone derivative was first determined by Hans Brockmann in 1936. The (R)-enantiomer of alkannin is known as shikonin, and the racemic mixture of the two is known as shikalkin.

Biosynthesis

The enzyme 4-hydroxybenzoate geranyltransferase utilizes geranyl diphosphate and 4-hydroxybenzoic acid to produce 3-geranyl-4-hydroxybenzoic acid and diphosphate. These compounds are then used to form alkannin.

Research

Because the root bark (cork layers) of Alkanna tinctoria contains large amounts of red naphthoquinone pigments, including alkannin, the roots of these plants are red-purple. When extracted from fresh tissues, the pigment gradually darkens over several days, finally forming black precipitates, which are thought to be polymers.

References

References

  1. ''[[The Merck Index]]'', 11th Edition, '''243'''
  2. [http://www.foodstandards.gov.au/_srcfiles/Additives%20alpha.pdf Additives] {{Webarchive. link. (2011-04-06 , [[Food Standards Australia New Zealand]])
  3. (1918). "Dispensatory of the United States of America".
  4. H. Brockmann. (1936). "Die Konstitution des Alkannins, Shikonins und Alkannans". Justus Liebigs Ann. Chem..
  5. Shmuel Yannai. (2012). "Dictionary of Food Compounds". CRC Press.
  6. Vassilios P. Papageorgiou. (1999). "The Chemistry and Biology of Alkannin, Shikonin, and Related Naphthazarin Natural Products". Angew. Chem. Int. Ed..
  7. (2017). "''Lithospermum erythrorhizon'' cell cultures: Present and future aspects". Plant Biotechnology.
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food-colorings 1,4-naphthoquinones terpeno-phenolic-compounds articles-containing-video-clips hydroxynaphthoquinones secondary-alcohols 3-hydroxypropenals-within-hydroxyquinones alkene-derivatives
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