Change in isoflavone concentration of soybean (Glycine max L.) seeds at different growth stages

This study was conducted to determine the fluctuating levels of isoflavone in soybean (Glycine max L.) seeds of six varieties at different development stages. The average concentration of total isoflavone in the fully matured seed was 669 μg g-1, whereas those in the seeds of the R5 (beginning), R6 (green full-sized) and R7 (onset of physiological maturity) stages were 145, 296 and 611 μg g-1, respectively. Sowonkong variety was highest in total isoflavone content of the fully matured and the R7 seed among all the varieties. In all six varieties, total isoflavone levels at the R7 stage were higher than those of R5 and R6 stages. Total isoflavone concentrations rapidly increased as growth stages transitioned from R5 to R7, as indicated by a positive correlation (r = 0.80***) between the total isoflavone and growth stages. Overall, total isoflavone levels were similar between R7 and the full maturity stages. Of the various isoflavone derivatives, acetylglucoside and aglycon were not significantly correlated with total isoflavone concentrations. However, glucoside (r = 0.97***), malonylglucoside (r = 0.99***), TGIN (genistein + genistin + malonylgenistin + acetylgenistin, r = 0.93***) and TDIN (daidzein + daidzin + malonyldaidzin + acetyldaidzin, r = 0.99***) were very highly correlated with total isoflavone concentrations. As a result, they constituted most of the total isoflavones in the soybean seeds at R5, R6, R7, and full maturity stages.