Response surface methodology (RSM) in conjunction with central composite design (CCD) was performed to optimize the extraction of flavonoids from soybean seeds (Glycine max L.). The  maximum yield of total flavonoid content (TFC) and the 2,2-diphenyl-1-pierylhydrazyl (DPPH) free-radical scavenging potential were used as quality indicators.  The extraction was carried out three cycles by using acetone as solvent.  The range of the independent variables, 

namely acetone concentration (60-80%, v/v),  the ratio of solvent and material (6:1-10:1, v/w), the  extraction temperature (30-50°C) and time  for each cycle  (180-240 minutes) were identified by a first set of single  and two  factor experiments. The optimum conditions for extraction were found to be at acetone concentration  69%, the  ratio of solvent and material 8:1  (v/w),  extraction temperature 42°C and  184  minutes  for  each  cycle  extraction. Under these optimized conditions, the experimental yields  of  TFC and DPPH free-radical scavenging potential  were  respectively 2.1  ± 0.01 mg  QE/g DW and 79.49 ± 0.16% which were  in close agreement with predicted values,  This  indicates  the suitability of the models developed and the success of RSM in optimizing the extraction conditions.