C.I. Natural red 20
3D model (JSmol)
|E number||E103 (colours)|
|Molar mass||288.299 g·mol−1|
|Appearance||Red-brown crystalline prisms|
|Melting point||149 °C (300 °F; 422 K)|
|Boiling point||567 °C (1,053 °F; 840 K)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|3.0 g/kg (mice)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Alkannin is a natural dye that is obtained from the extracts of plants from the borage family Alkanna tinctoria that are found in the south of France. The dye is used as a food coloring and in cosmetics. It is used as a red-brown food additive in regions such as Australia, and is designated in Europe as the E number E103, but is no longer approved for use. Alkannin has a deep red color in a greasy or oily environment and a violet color in an alkaline environment.
The chemical structure as a naphthoquinone derivative was first determined by Brockmann in 1936. The enantiomer of alkannin is known as shikonin, and the racemic mixture of the two is known as shikalkin.
The enzyme 4-hydroxybenzoate geranyltransferase utilizes geranyl diphosphate and 4-hydroxybenzoate to produce 3-geranyl-4-hydroxybenzoate and diphosphate. These compounds are then used to form alkannin.
Alkannin is an antioxidant and has an antimicrobial effect against Staphylococcus aureus and Staphylococcus epidermidis. It is also known to have wound healing, antitumor, and antithrombotic properties.
- The Merck Index, 11th Edition, 243
- Additives Archived 2011-04-06 at the Wayback Machine, Food Standards Australia New Zealand
- "Current EU approved additives and their E Numbers", Food Standards Agency website, retrieved 15 Dec 2011
- H. Brockmann (1936). "Die Konstitution des Alkannins, Shikonins und Alkannans". Justus Liebigs Ann. Chem. 521: 1–47. doi:10.1002/jlac.19365210102.
- Shmuel Yannai (2012). Dictionary of Food Compounds. CRC Press. p. 478.
- Vassilios P. Papageorgiou; Andreana N. Assimopoulou; Elias A. Couladouros; David Hepworth; K. C. Nicolaou (1999). "The Chemistry and Biology of Alkannin, Shikonin, and Related Naphthazarin Natural Products". Angew. Chem. Int. Ed. 38 (3): 270–300. doi:10.1002/(SICI)1521-3773(19990201)38:3<270::AID-ANIE270>3.0.CO;2-0.
- A.N. Assimopoulou; D. Boskou; V.P. Papageorgiou (2004). "Antioxidant activities of alkannin, shikonin and Alkanna tinctoria root extracts in oil substrates". Food Chemistry. 87 (3): 433–438. doi:10.1016/j.foodchem.2003.12.017.
- Wiench, B; Eichhorn, T; Paulsen, M; Efferth, T (2012). "Shikonin Directly Targets Mitochondria and Causes Mitochondrial Dysfunction in Cancer Cells". Evidence-Based Complementary and Alternative Medicine. 2012: 726025. doi:10.1155/2012/726025. PMC 3478753. PMID 23118796.