Phenolic Constituents, Ascorbic Acid, Tocopherols and Antioxidant Activity of Soybean Genotypes with Varying Seed Coat Colour

In order to determine the antioxidant potential, seeds of 20 soybean (Glycine max. L.) genotypes varying in seed coat colour viz. black, brown, green and yellow were compared for their phenolic constituents, vitamins and antioxidant activities. Genotypes with different seed coat colour showed wide variations of total phenols (TP) from 9.3–23.56 mg gallic acid equivalents, total flavonols (TF) 7.77 to 20.25 mg/g rutin, orthodihydroxyphenols (OHP) 0.232 to 0.835 mg/g catechol equivalents, anthocyanins 0.92 to 3.21 mg/g, ascorbic acid 0.124–0.302 mg/100g and tocopherols 6.22 to 30.66 mg/100g. Mean TP, TF, and OHP were significantly higher in black group as compared to brown, green and yellow soybeans. Ferric reducing antioxidant power (FRAP), 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, hydroxyl ion and nitric oxide scavenging capacity of soybean genotypes were significantly different not only between groups but also among genotypes within each group.