Properties of red pigments prepared from geniposidic acid and amino acids

Red pigments formed from geniposide and amino acids were studied. Geniposide, the principal iridoid glucoside contained in the fruit of Gardenia jasminoides Ellis, was hydrolysed to geniposidic acid as a precursor for the pigment. The pigments prepared anaerobically with arginine or glutamic acid under acidic conditions with a large excess of citric acid, were reddish purple and had properties governed by the electrostatic character of the amino acid. Relative molecular masses of these pigments were determined to be several thousand by gel filtration. The pigments showed good stability to heat and pH, but were gradually bleached by light. The safety of the pigments was evaluated by studing their oral acute and the 5-month oral toxicity of arginine-red pigment using mice. The pigments were considered to be of low toxicity. © 1999 Society of Chemical Industry