Potential of local black soybean as a source of the isoflavones daidzein and genistein

Daidzein and genistein are isoflavone compounds produced by soybean plants and have an important role in medical therapy. For the soybean crop itself, daidzein and genistein contribute as a defence mechanism against pathogen attack, and also as chemoattractants for Rhizobium bacteria. The development of black soybean varieties that have high levels of daidzein and genistein is required for functional food and industrial raw materials. The objective of this study was to identify the content of daidzein and genistein in local black soybean genotypes. Thirty-four black soybean genotypes were planted in a randomised block design. Daidzein and genistein content were measured in black soybean seeds using high-performance liquid chromatography. In the 34 black soybean genotypes, daidzein contents (0.01-0.21 mg g-1) were more variable than genistein (0.02-0.03 mg g-1). Compared to genistein, daidzein content was higher in 31 genotypes (0.03-0.21 mg g-1) and the other in three genotypes (0.01-0.02 mg g-1). The UP106 genotype showed the highest content of daidzein (2.06 mg g-1), while UP115 showed the highest genistein content (0.29 mg g-1). UP104 had the highest daidzein content per plant because it had a higher seed weight per plant. The UP106, UP104 and UP115 genotypes have potential to be developed as sources of daidzein and genistein.