Characterization and quantification of saponins and flavonoids in sprouts, seed coats and cotyledons of germinated black beans.

Saponins, flavonols and isoflavones were quantified in sprouts, cotyledons and seed coats of black beans (Phaseolus vulgaris L.) subjected to germination over five days. Sprouts had a higher concentration of saponins compared to cotyledons or seed coats (p<0.05). The saponins concentration in hilum increased 2.3-fold after soaking. After the first day of germination, the saponin concentration in sprouts and cotyledons increased 1.9 and 2.1-fold, respectively. Additional germination days decreased the amount of the most abundant soyasaponins in black bean sprouts. Flavonols and isoflavones were associated with seed coats and less than one third of the initial amount remained after the soaking process. The concentrations of flavonols were also reduced during germination process. Aglycones were detected only after soaking and their concentration remained unchanged during germination. Genistein was detected only after three days of germination. In general, one-day germinated black beans could be recommended for increasing the concentration of saponins and non-glycosylated flavonols in sprouts and seed coats, respectively.