What molecule am I?
Carminic acid is a naturally occurring organic molecule whose structure consists of 9,10-anthraquinone-2-carboxylic acid 鈥渄ecorated鈥� with a methyl group, a glucopyranose, and four hydroxyls. It is found in several species of scale insects known as cochineals, including听Dactylopius coccus听(Western Hemisphere),听Porphyrophora hamelii听(Armenia), and听Porphyrophora polonica听(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鈥檚 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鈥揳pproved 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鈥� paints, and a pigment for inks. In its cochineal dye form, you can even use it to听听for cards and envelopes for Valentine鈥檚 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 4 | H302鈥擧armful if swallowed |  |
| Serious eye damage/eye irritation, category 2A | H319鈥擟auses serious eye irritation | |
Specific target organ toxicity, single exposure, respiratory tract irritation, category 3 | H335鈥擬ay cause respiratory irritation | |
*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.听
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Carminic acid
fast facts
| CAS Reg. No. | 1260-17-9 |
nomenclature | 2-Anthracene-carboxylic acid, 7-尾-D-glucopyranosyl-9,10-dihydro-3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxo- |
| Empirical formula | C22H20O13 |
| Molar mass | 492.39听g/mol |
| Appearance | Red crystals; bright red to dark purple powder |
| Melting point | 136 掳C (dec.) |
| Water solubility | 1.3 g/L |
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