Carminic acid (C22H20O13) is a red glucosidal hydroxyanthrapurin that occurs naturally in some scale insects, such as the cochineal, Armenian cochineal, and Polish cochineal. The insects produce the acid as a deterrent to predators. An aluminum salt of carminic acid is the coloring agent in carmine. Synonyms are C.I. 75470 and C.I. Natural Red 4.

Carminic acid[1]
Chemical structure of carminic acid[citation needed]
Ball-and-stick model of carminic acid[citation needed]
IUPAC name
7-(β-D-Glucopyranosyl)-3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid
Other names
Carminic acid
C.I. Natural Red 4
C.I. 75470
CI 75470
3D model (JSmol)
ECHA InfoCard 100.013.658
EC Number
  • 215-023-3
E number E120 (colours)
Molar mass 492.38 g/mol
Melting point 120 °C (248 °F; 393 K) (decomposes)
Acidity (pKa) 3.39, 5.78, 8.35, 10.27, 11.51[2]
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

The chemical structure of carminic acid consists of a core anthraquinone structure linked to a glucose sugar unit. Carminic acid was first synthesized in the laboratory by organic chemists in 1991.[3]

It was previously thought that it contains α-D-glucopyranosyl residue,[1] which was later redetermined to be the β-D-glucopyranosyl anomer.[4]


  1. ^ a b Merck Index, 11th Edition, 1989, 1850.
  2. ^ Atabey, Hasan; Sari, Hayati; Al-Obaidi, Faisal N. (28 April 2012). "Protonation Equilibria of Carminic Acid and Stability Constants of Its Complexes with Some Divalent Metal Ions in Aqueous Solution". Journal of Solution Chemistry. 41 (5): 793–803. doi:10.1007/s10953-012-9830-7.
  3. ^ Allevi, P.; et al. (1991). "The First Total Synthesis of Carminic Acid". Journal of the Chemical Society, Chemical Communications. 18 (18): 1319–1320. doi:10.1039/C39910001319.
  4. ^ Fiecchi, Alberto; Galli, Mario Anastasia Giovanni; Gariboldi, Pierluigi (1981-03-01). "Assignment of the β configuration to the C-glycosyl bond in carminic acid". The Journal of Organic Chemistry. 46 (7): 1511. doi:10.1021/jo00320a061. ISSN 0022-3263.