Antioxidant Capacity and Isoflavone Content in Seeds of Five Edamame (Glycine maxL. Merrill) Cultivars

Abstract

Edamame, immature or vegetable soybeans, has received growing attention in the US largely due to its purported health benefits from antioxidants and isoflavones. However, previous studies predominately focused on antioxidant capacity and isoflavone content of fully mature, dry, grain or agronomic soybeans. The purpose of this study was to measure the antioxidant and isoflavone contents of five commercially available edamame cultivars grown in Painter, VA in 2008 and 2009. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay results ranged from a low of 24.1 µmol/g sample trolox equivalent (TE) for ‘Midori Giant’ to a high of 46.5 µmol/g for ‘Sunrise’ in 2008. In 2009, DPPH assay results ranged from 13.0 µmol/g TE for ‘Midori Giant’ to 18.0 µmol/g TE for ‘BeSweet2015’. In 2008, oxygen radical absorption capacity (ORAC) assay results ranged from 20.4 µmol/g TE for ‘Midori Giant’ to 37.2 µmol/g TE for ‘BeSweet2015’; although there were no significant differences. In 2009, ORAC assay results ranged from 26.0 µg/g TE for ‘Sunrise’ to 40.2 µg/g TE for ‘BeSweet292’. Total isoflavone content ranged from 144.6 to 529.2 µg/g and 127.2 to 315.5 µg/g in 2008 and 2009, respectively. Malonyl genistin was the most abundant isoflavone. Antioxidant and isoflavone contents varied by year and cultivar. ‘Midori Giant’ had relatively low antioxidant capacity both years, but the highest isoflavone content. ‘BeSweet2015’ and ‘BeSweet2001’ had relatively high antioxidant capacities, but lower isoflavone contents.