The preparation and properties of oil- soluble derivatives of carminic acid

Cochineal extract( Dactylopius coccus costa) is one of the most valuable water- soluble natural red pigments.In order to improve its solubility in organic solvents and oil,the method of chemical structure modification was applied.Five oil- soluble derivatives of carminic acid which was the main ingredient of cochineal extract were designed and prepared through two- step reactions in this paper.The structure of the products was characterized by fourier transform infrared spectroscopy( FTIR),the solubility and stable properties in the presence of acid,alkali,light,heat,or metal ions had been investigated. The results showed that ester group and alkyl group were introduced to carminic acid which were proved by FTIR.The five products could easily be dissolved in organic solvents and oil.Descending order of their solubility in the corn oils was CE5 > CE2 > CE4 > CE1> CE3.Solubility of the derivative CE5 reached 12.8 g / L.The products were stable in the presence of light and have excellent thermal stability.Metal ion Cu~(2+),Fe~(3+)and Al~(3+)could make products fade,but products graced in the presence of Na+and Mg~(2+).With the heritage of dyeing ability of cochineal extract,the five derivatives were proved with good stability and high solubility in oil,therefore,the search had become important to further application of cochineal extract.