Carminic acid - WikiHQ

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.

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.

left|thumb|Female [[Cochineal|Dactylopius coccus on prickly pear cactus photographed by Frank Vincentz.]]

Harvesting from cochineals

Carminic acid is commonly harvested from an American species scaled insects called Dactylopius coccus (or cochineals). Cochineals are parasitic scaled insects which are abundantly found on their host plants, the prickly pear cactus native to Mexico and South America. The insects are either cultivated or harvested from wild populations, mainly for the wingless females of the species which attach themselves to the cactus and outnumber the winged males of the species two hundred to one. Classically, cultivated species were grown from eggs placed by workers onto the cactus leaves and left to grow. There the female cochineals would remain immobile for about 3 months until being brushed off, collected, and dried for shipping. In Eisner's 1980 paper, he notes that the red colour of the carminic acid released when the cochineals are crushed could also be a visual aposematic deterrent for predators as well. The pyralid moth larva (Laetilia coccidivora) is one such predator which feeds on cochineals, sequestering their prey's carminic acid in their own body for defense against predators.

The biosynthesis of carminic acid can be divided into three stages. The initiation stage involves transferases that load acetyl (AT) and malonyl-CoA (MCAT) to the acyl carrier protein (ACP) forming acetyl and malonyl-ACP, respectively. The acetyl-ACP acts as a priming unit for the decarboxylative condensation with malonyl-CoA catalyzed by a ketoacyl synthase (KS) protein. The resulting acetoacetyl ACP is the simplest polyketide produced by this pathway, and it is subsequently condensed with six more malonyl-ACP units before cyclizing.