Alkannin

Alkannin is a natural dye that is obtained from the extracts of Alkanna tinctoria which is found in the south of France. The dye is used as a food coloring and in cosmetics; 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 Brockmann in 1936. The R-enantiomer of alkannin is known as shikonin, and the racemic mixture of the two is known as shikalkin.

Alkannin
Names
Preferred IUPAC name
5,8-Dihydroxy-2-[(1S)-1-hydroxy-4-methylpent-3-en-1-yl]naphthalene-1,4-dione
Other names
  • C.I. Natural red 20
  • Alkanet extract
  • Anchusaic acid
  • Anchusin
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.007.497
E number E103 (colours)
KEGG
PubChem CID
UNII
  • InChI=1S/C16H16O5/c1-8(2)3-4-10(17)9-7-13(20)14-11(18)5-6-12(19)15(14)16(9)21/h3,5-7,10,17-19H,4H2,1-2H3/t10-/m0/s1 Y
    Key: NEZONWMXZKDMKF-JTQLQIEISA-N Y
  • InChI=1/C16H16O5/c1-8(2)3-4-10(17)9-7-13(20)14-11(18)5-6-12(19)15(14)16(9)21/h3,5-7,10,17-19H,4H2,1-2H3/t10-/m0/s1
SMILES
  • O=C\2c1c(O)ccc(O)c1C(=O)/C(=C/2)[C@@H](O)CC=C(C)C
Properties
C16H16O5
Molar mass 288.299 g·mol−1
Appearance Red-brown crystalline prisms
Density 1.15 g/mL
Melting point 149 °C (300 °F; 422 K)
Boiling point 567 °C (1,053 °F; 840 K)
Sparingly soluble
Hazards
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).
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Infobox references
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