The history, chemistry and modes of action of carmine and related dyes
- 1 January 2007
- journal article
- review article
- Published by Taylor & Francis Ltd in Biotechnic & Histochemistry
- Vol. 82 (4-5), 173-187
- https://doi.org/10.1080/10520290701704188
Abstract
Carmine has been used in biological staining to demonstrate selectively nuclei, chromosomes or mucins, depending on the formulation. Throughout its history in science, complaints and frustrations have been expressed about dye quality. Inconsistencies in dye quality or identity have prevented thorough understanding of staining mechanisms and have caused many stain solutions to behave unsatisfactorily. The aim of this review is to (1) detail causes of these problems, which are rooted in history, geography and production, (2) offer ways to minimize problems and (3) provide modern explanations for stain behavior. Carmine is a “semi-synthetic” dye, i.e., a complex of aluminum and the natural dye cochineal (carminic acid). Carmine shows considerable batch-to-batch variability. Geography, politics, history, agricultural practices and iconography all contribute to the variability of cochineal. In addition, widely divergent manufacturing methods are used to produce carmine. Also, confusion in terminology has led to mislabeling. Pressure from the food industry for a more satisfactory colorant for acidic foods led to the introduction of a new dye, aminocarminic acid, which could enter the biological market inadvertantly. Improved methods of analysis should help the certification process by the Biological Stain Commission. Further standardization could be achieved by replacing most of the methods of solubilizing carmine. The majority of these methods use heat, which is likely to damage the dye molecule. Fortunately, carmine is readily dissolved by raising the pH of the aqueous solvent above 12, and a new form of the dye, now available commercially, is soluble in water without the need for heat or pH adjustment. Chemical structures and physical properties of carminic acid, carmine, aminocarminic acid and kermesic acid are reviewed. A new configuration for carmine is proposed, as well as possible changes to carminic acid and carmine molecules as a result of decomposition caused by heating. Each of the major classes of carmine-based stains is described as are possible mechanisms of attachment to specific substrates. Glycogen binds carmine through hydrogen bonding, and it is here that carmine decomposed by heat could have the greatest detrimental impact. Nuclei and chromosomes are stained via coordination bonds, perhaps supplemented by hydrogen bonds. Finally, acidic mucins react ionically with carmine. Specificity in the latter case may be due to unique polymeric carmine molecules that form in the presence of aluminum chloride.Keywords
This publication has 12 references indexed in Scilit:
- AnnouncementBiotechnic & Histochemistry, 2006
- Color Quality of Pigments in Cochineals (Dactylopius coccusCosta). Geographical Origin Characterization Using Multivariate Statistical AnalysisJournal of Agricultural and Food Chemistry, 2004
- Removal of ammonium and phosphates from wastewater resulting from the process of cochineal extraction using MgO-containing by-productWater Research, 2003
- Structure of Acid-Stable Carmine.Food Hygiene and Safety Science (Shokuhin Eiseigaku Zasshi), 2002
- High-performance liquid chromatographic separation of carminic acid, α- and β-bixin, and α- and β-norbixin, and the determination of carminic acid in foodsJournal of Chromatography A, 1996
- Defensive use of an acquired substance (carminic acid) by predaceous insect larvaeCellular and Molecular Life Sciences, 1994
- Red Cochineal Dye (Carminic Acid): Its Role in NatureScience, 1980
- A Simple Assay Procedure for Carmine and Carminic Acid SamplesStain Technology, 1974
- On the structure of carminic acid and carmineHistochemistry and Cell Biology, 1971
- Metal Complexes of Alizarin I—The Structure of the Calcium–Aluminium Lake of AlizarinJournal of the Society of Dyers and Colourists, 1963