Title: Alkannin
CAS Registry Number: 517-88-4
CAS Name: 5,8-Dihydroxy-2-[(1S)-1-hydroxy-4-methyl-3-pentenyl]-1,4-naphthalenedione
Additional Names: (-)-5,8-dihydroxy-2-(1-hydroxy-4-methyl-3-pentenyl)-1,4-naphthoquinone; anchusa acid; anchusin; alkanna red; alkanet extract; (1-hydroxy-3-isohexenyl)naphthazarine; 2-(1-hydroxy-4-methyl-3-pentenyl)-5,8-dihydroxy-1,4-naphthoquinone; C.I. Natural Red 20; C.I. 75530
Molecular Formula: C16H16O5
Molecular Weight: 288.30
Percent Composition: C 66.66%, H 5.59%, O 27.75%
Literature References: Isoln from the root of Alkanna tinctoria Tausch, Boraginaceae: Brockmann, Ann. 521, 1 (1936); Toribara, Underwood, Anal. Chem. 21, 1352 (1949). Absolute configuration: Arakawa, Nakagaki, Chem. Ind. (London) 1961, 947. Toxicity study: L. Majlathova, Nahrung 15, 505 (1971), C.A. 76, 122513j (1972).
Properties: Brownish-red prisms with a metallic sheen from benzene, mp 149°. Can be sublimed in high vac at 140-150°. [a]20Cd -165° (benzene); -226° (chloroform). Also reported as -254 ± 7° (chloroform) (Toribara). Sol in organic solvents, sparingly sol in water. Buffered aq solns are red at pH 6.1; purple at pH 8.8; blue at pH 10.0. LD50 in male, female mice, rats (g/kg): 3.0 ± 1.0; 3.1 ± 0.1; >1.0 orally (Majlathova).
Melting point: mp 149°
Optical Rotation: [a]20Cd -165° (benzene); -226° (chloroform). Also reported as -254 ± 7° (chloroform) (Toribara)
Toxicity data: LD50 in male, female mice, rats (g/kg): 3.0 ± 1.0; 3.1 ± 0.1; >1.0 orally (Majlathova)
Derivative Type: (+)-Form
Additional Names: Shikonin
Derivative Type: (±)-Form
Additional Names: Shikalkin
Use: Red dye for cosmetics and food; spectrophotometric microdetermination of beryllium.
Therap-Cat: Astringent.
Keywords: Astringent.
Alkofanone Allantoin Allenolic Acid Allethrins Allidochlor

CAS number 517-88-4 N
PubChem 72521
ChemSpider 65430 YesY
KEGG C10292 YesY
Jmol-3D images Image 1
Molecular formula C
Molar mass 288.29 g/mol
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
Solubility in water Sparingly soluble
LD50 3.0 g/kg (mice)
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

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,[2] and is designated in Europe as the E number E103, but is no longer approved for use.[3]

The chemical structure as a naphthoquinone derivative was first determined by Brockmann in 1936.[4] Alkannin has a deep red color in a greasy or oily environment and a violet color in an alkaline environment. Biosynthetically, alkannin is produced in plants from the intermediates 4-hydroxybenzoic acid and geranyl pyrophosphate.[5]

Alkannin is an antioxidant[6] and has an antimicrobial effect against Staphylococcus aureus and Staphylococcus epidermidis. It is also known to have wound healing, antitumor, and antithrombotic properties.[5]