Content and composition of isoflavonoids in mature or immature beans and bean sprouts consumed in Japan

The content of 9 types of isoflavonoids (daidzein, glycitein, genistein, formononetin, biochanin A, coumestrol, daidzin, glycitin and genistin) in 34 domestic or imported raw beans including soybeans, 7 immature beans and 5 bean sprouts consumed in Japan were systematically analyzed. Each isoflavonoid was analyzed in total after acid hydrolysis to the aglycone, and intact individual isoflavonoids were also analyzed without hydrolysis. After the sample clean up, daidzein, glycitein, genistein, formononetin, biochanin A, daidzin, glycitin and genistin were determined by HPLC with a diode array detector and coumestrol was determined by spectrofluorimetry. The content and composition of isoflavonoids varied greatly between soybean sprouts, immature soybeans and mature beans of the same type but of different source. Isoflavonoid content was highest in mature soybeans. The composition of isoflavonoids differed in each growth stage of soybeans. In other beans, the largest content of isoflavonoids was found in mature chickpeas, but this value was less than 1/27 of the isoflavonoid content in mature soybeans. Thus, the contribution of beans other than soybeans to the daily intake of isoflavonoids in a Japanese diet is negligible.