Preparation and stability of ethanol-soluble red pigment from the bark of Larix gmelini

The ethanol-soluble proanthocyanidin red pigment was prepared from raw material of the bark of Larix gmelini.The red pigment was extracted by using 70 % EtOH,and then the extract was purified by using petroleum ether.The yield of the pigment reached 6.29 %.Using the pigment as the experimental material,its chemical and physical characteristics and the effects of light,hot,acid,alkalis on its stabitity were studied.The results showed that it had characteristic absorption spectrum similar with proanthocyanidin between 255-278 nm and at 550 and 577 nm.It was soluble in polarity solvent such as methanol and alcohol,and its colour value was higher than 250.The colour of the pigment was bright red when pH was 3-8 as well as in sun light.The pigment was stable in different concentrations of ethanol,also when it was heated for 1 h below 100 ℃.The stability of the pigment was influenced by Fe²⁺,Fe³⁺ and Al³⁺,but not by Ca²⁺,Ba²⁺,Na⁺,Mg²⁺,Cl^-,SO₄^2-.