Carminic acid (C22H20O13) is a red glucosidal hydroxyanthrapurin that occurs naturally in some scale insects, such as the cochineal and the Polish cochineal. The insects produce the acid as a deterrent to predators. Carminic acid is the colouring agent in carmine. Synonyms are C.I. 75470 and C.I. Natural Red 4. The chemical structure of carminic acid consists of a core anthraquinone structure linked to a glucose sugar unit. The activation of Dactylopius coccus (Costa) hemolymph with microbial polysaccharide molecules was studied. Hemolymph incubated in the presence of laminarin, zymosan, and N-acetyl glucosamine produced a dark fibrillar precipitated, and the red pigment (carminic acid) was consumed (measured spectrophotometrically at 495 nm). Lipopolysaccharide (LPS) did not induce any response. The reaction was inhibited with millimolar concentrations of serine and cysteine protease inhibitors, EGTA and phenyl thiourea.
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