Abstract
One anthocyanin (cyanidin 3-monoglucoside) had been isolated from the seed coat of black soybean by Kuroda and Wada. But according to the paper chromatographic test on crude seed coat extract of black soybean, it was found that the dark red color was due to two kinds of anthocyanins. For the identification of these anthocyanin pigments, the seed coat of black soybean was treated as follows.
From seed coat extract with 1% cold methanolic hydrochloric acid the pigment was precipitated with basic lead acetate solution. The lead salts were then converted into chloride by treatment with 5% methanolic hydrochloric acid. After concentration under reduced pressure, two pigments were separated from each other by mass paper chromatographic method. After purification on polyamide columns by elution with methanol, each pigment (A and B) was crystallized from 1% methanolic HCl.
Rf value of each pigment was determined by using the authenic specimens (cyanidin, chrysanthemin, delphinidin, delphinidin 3-monoglucoside etc). By acid hydrolysis of crystalline pigmints, one pigment produced glucose and cyanidin, the other glucose and delphinidin. By means of elementary analysis, partial acid hydrolysis, absorption spectra and other chemical properties, it was found that these pigments were cyanidin 3-monoglucoside (chrysanthemin) and delphinidin 3-monoglucoside.
