Carminic acid
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, a pigment. Natives of Peru had been producing cochineal dyes for textiles since at least 700 CE. Synonyms are C.I. 75470 and C.I. Natural Red 4.
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IUPAC name
7-(β-D-Glucopyranosyl)-3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid | |
Systematic IUPAC name
3,5,6,8-Tetrahydroxy-1-methyl-9,10-dioxo-7-[(2S,3R,4R,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]-9,10-dihydroanthracene-2-carboxylic acid | |
Other names
Carminic acid C.I. Natural Red 4 C.I. 75470 CI 75470 | |
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ECHA InfoCard | 100.013.658 |
EC Number |
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E number | E120 (colours) |
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Properties | |
C22H20O13 | |
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 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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. In 2018, researchers genetically engineered the microbe Aspergillus nidulans to produce carminic acid.
It was previously thought that it contains α-D-glucopyranosyl residue, which was later redetermined to be the β-D-glucopyranosyl anomer.