Isoflavone characterization and antioxidant activity of Ohio soybeans

Seventeen Ohio soybeans were screened for isoflavone content and antioxidant activity. Isoflavone content was determined by C-18 reversed phase high-performance liquid chromatography coupled with a photodiode array detector. Antioxidant activities of soybean extracts were measured using 2,2-diphenyl-1-picryl-hydrazyl (DPPH) free radical and photochemiluminescence (PCL) methods. The highest and lowest total isoflavone contents were 11.75 and 4.20 mumol/g soy, respectively, while the average was 7.12 mumol/g soy. Antioxidant activities of soybean extracts ranged from 7.51 to 12.18 mumol butylated hydroxytoluene (BHT) equivalent/g soy using the DPPH method. Lipid and water soluble antioxidant activities of soybean extracts ranged from 2.40 to 4.44 mumol Trolox equivalent/g soy and from 174.24 to 430.86 mumol ascorbic acid equivalent/g soy, respectively, using the PCL method.