Carminic acid

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February 14, 2022
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Carminic acid is a naturally occurring organic molecule whose structure consists of 9,10-anthraquinone-2-carboxylic acid “decorated” with a methyl group, a glucopyranose, and four hydroxyls. It is found in several species of scale insects known as cochineals, including Dactylopius coccus (Western Hemisphere), Porphyrophora hamelii (Armenia), and Porphyrophora polonica (north-central Europe).

In 1894, noted British dye chemist Henry Edward Schunk, working in Germany, isolated carminic acid from cochineals. German chemist Otto Dimroth reported its structure in 1920; and Indian chemists S. B. Bhatia and K. Venkataraman corrected the placement of the carboxyl group in Dimroth’s structure in 1965.

Cochineal insects use carminic acid to repel other insects. But for centuries, cochineals have been valuable to humans for providing carminic acid to use on its own or to make cochineal dyes. When carminic acid is treated with with aluminum and/or calcium salts, it forms complexes that are familiarly called carmine, carmine lake, crimson lake, or even the eponymous cochineal1. The dye is used for textiles and as a US Food and Drug Administration–approved food, cosmetic, and drug colorant, although some people exhibit allergic reactions to it.

Free carminic acid has been used as a bacteriological stain, an ingredient for artists’ paints, and a pigment for inks. In its cochineal dye form, you can even use it to make your own colored paper for cards and envelopes for Valentine’s Day!

1. CAS Reg. No. 1343-78-8.

Originally the Molecule of the Week for February 5, 2007

Carminic acid hazard information*

Hazard class**GHS code and hazard statement
Acute toxicity, oral, category 4H302—Harmful if swallowedChemical Safety Warning
Serious eye damage/eye irritation, category 2AH319—Causes serious eye irritationChemical Safety Warning

Specific target organ toxicity, single exposure, respiratory tract irritation, category 3

H335—May cause respiratory irritationChemical Safety Warning

*Most safety data sheets state that carminic acid is not a hazardous substance or mixture. The information given here was found in only one SDS.
**Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. Explanation of pictograms.

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Carminic acid
fast facts

CAS Reg. No.1260-17-9
2-Anthracene-carboxylic acid, 7-β-D-glucopyranosyl-9,10-dihydro-3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxo-
Empirical formulaC22H20O13
Molar mass492.39 g/mol
AppearanceRed crystals; bright red to dark purple powder
Melting point136 °C (dec.)
Water solubility1.3 g/L
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