Cochineals chemistry

Lloyd, A.G., Extraction and chemistry of cochineal, Food Chem., 5, 91, 1980. Schul, I.J., An ancient but still young colorant, in Proceedings of First International Symposium on Natural Colorants. Francis, F.J., Ed., Hereld Organization, Hamden, CT, 1993. 

When the Spanish conquistadors arrived in America they were impressed with the brilliant red fabrics worn by the Aztecs. Then the Spaniards learned that the Aztecs knew of another dye-producing insect — the cochineal. A type of cactus known as opuntia, plentiful in South America, was the ideal breeding ground for these insects, and the females produced the dye. The Aztecs had developed the technique of sweeping the insects off the leaves into hot water to kill them before drying the corpses in the sun. There was no gender separation the useless males were sacrificed to the fascinating chemistry of the female. 

Runge s materials are animated. They act wilfully, it would seem. Chemicals combine or unite. They marry and split. Runge s scientific language is one of affinity and repulsion. In his text of 1834, Colour Chemistry, Founded on the Chemical Relations of Cotton Thread to Salts and Acids, he notes, for example, the affinity of cotton for different dye substances. These characteristics - such as the instability of cochineal red - form a sort of personality. In the opening pages of Basic Outline of Chemistry of 1848, Runge notes that there are now 59 elements in the world. Each of these has its own characteristics and displays a specific behaviour The chemical behaviour of an element depends on its chemical activity, and this activity is its peculiar expression of life when confronted by another element. 20... 

Apart from the derivatives of p-carotene, other pigments are the anthocyanins, the chlorophylls, cochineal, the betalaines, turmeric, caramel and riboflavin. In this account the historical background in brief, the chemistry of these pigments, their extraction from natural sources and their synthesis will be discussed. The present permitted natural substances and nature-identical synthetic materials (also described by the Food and Drugs Administration, the FDA, as colorants exempt from certification ) is quite small in number. Reference is also made to colourants no longer listed but which have an historical organic chemical significance such as for example brazilin and its relative haematoxylin. 

Cochineal extract (Colour Index 75470, E 120)is the final alcohol-free material obtained after aqueous ethanolic extraction of the dried bodies of the female scale insect Dactylopius coccus Costa which lives on cacti such as Opuntia or Nopalea coccinellifera a species indigenous to Peru and Mexico, although also found in the Canary Islands. In practice a simpler procedure consists of aqueous alkaline extraction. The colourant principle is carminic acid which is more well-known in the form of carmine, an aluminium chelate of carminic acid, a material insoluble in water and stable on the acidic side. A uv spectrophotometric study has been made (ref. 21). Thin layer chromatography of cochineal has been examined on acetylated cellulose with the solvent system, ethyl acetate-tetrahydrofuran-water (6 35 47) in which the Rf was 0.94 (refs.22,23). The history of the chemistry of cochineal has been discussed (ref.24). 

Red Colorants. The most important class of pre-Perkin colorants, from the coordination chemistry point of view, is the red colorants. All of the major red colorants, whether of animal or vegetable origin, are derivatives of anthraquinone (See Table II). The principal red coloring matter of madder is alizarin, or 1,2-dihydroxyanthraquinone. Natural madder contains a considerable amount of another colorant, purpurin, or 1,2,4-trihydroxyanthraquinone, which accounts for the various shades of red to purplish-red that can be obtained when different sources of madder are used. In almost every source that describes dyeing with anthraquinone derivatives, the use of a metallic salt is mentioned. The principal metals used were aluminum, iron, tin, and in later years, chromium. The resulting color on the fiber depended in large part upon the metal used since the dyes chelated with the metal ions. The colors of different chelate compounds with alizarin and cochineal are shown in Table HI. 

Pr n Prabhakaran is currently a PhD student in the Department of Advanced Materials at Hannam University Korea. He received his BS degree (2000) in Pure Chemistry from the University of Kerala in India and his MS degree (2003) in Applied Chemistry from Cochin University of Science and Technology, India. His current research deals with third-order NLO materials and two-photon direct writing of miaostructures. 

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