Composition of Isoflavone, Phytic Acid, and Saponins in Hypocotyls and Cotyledons of Six Traditional Korean Soybeans

The objective of present study was to examine the composition of functional components (isoflavones, phytic acid, and saponin) in hypocotyls and cotyledons of six traditional Korean soybeans, namely Cheongtae, Seoritae, Jinjoori, Subaktae, Yutae, and Huktae. Three 'family' of isoflavones, as four chemical structures were present in hypocotyls and cotyledons of six soybean cultivars: the aglycones genistein, daidzein, and glycitein; the glycosides genistin, daidzin, and glycitin; the acetylglycosides 6"-O-acetylgenistin, 6"-O-acetyldaidzin, and 6"-O-acetylglycitin; and the malonylglycosides 6"-O-malonylgenistin, 6"-O-malonyldaidzin, and 6"-O-malonylglycitin. Isoflavone contents of hypocotyls and cotyledons differed among the cultivars, and glucosides and malonylglucosides accounted for more than 90% of the total phytoestrogens, with the remaining $1\sim7%$ taken up by aglycones. Concentrations of isoflavones in cotyledons were approximately about $10\sim20%$ of respective hypocotyls. Contents of phytic acids in hypocotyls and cotyledons of the selected soybean cultivars were $1.21\sim1.70%$ and $2.59\sim3.01%$, respectively. Hypocotyls of Seoritae showed the lowest content of phytic acid with 1.21%, while cotyledons of Cheongtae showed the highest content with 3.01%. The sapogenol concentrations ranged from $13.58mg/100g\sim20.82mg/100g$ for hypocotyls and $0.95mg/100g\sim2.55mg/100g$ for cotyledons showing that concentrations of saponin are $7\sim10$ times higher in hypocotyls than in cotyledons of respective soybeans. For both hypocotyls and cotyledons the sapogenol A were present in higher concentrations than soyasapogenol B.