The aim of the present research was to determine an optimal acid hydrolysis condition using drying oven
and microwave assisted methods to estimate isoflavone contents by RP-HPLC in soybean. All isoflavone
glucosides were completely converted to their aglycones at 120 min for drying oven and 50 min for
microwave. Optimal extraction time of the highest isoflavone aglycone content after acid hydrolysis
was achieved in 3 h. These results indicated that the optimised hydrolysis and extraction conditions of
isoflavones in soybean were: soybean (1 g) hydrolysed by 10 ml of 1 N HCl at 100 C for 50 min using
microwave assisted acid hydrolysis method, and then 15 ml of EtOH was added to the mixture which
leaved alone for 3 h at room temperature for complete extraction. Thus, microwave is an easy, consumed
less time, and reliable acid hydrolysis method to estimate soybean isoflavones in comparison with drying
oven method.