Effect of different processing methods on antioxidant activity of underutilized legumes, Entada scandens seed kernel and Canavalia gladiata seeds

The present study is proposed to determine the antioxidant activity of raw and processed samples of underutilized legumes, Entada scandens seed kernel and Canavalia gladiata seeds. The indigenous processing methods like dry heating, autoclaving and soaking followed by autoclaving in different solutions (plain water, ash, sugar and sodium bicarbonate) were adopted to seed samples. All other processing methods than dry heat showed significant reduction in phenolics (2.9–63%), tannins (26–100%) and flavonoids (14–67%). However, in processed samples of E. scandens, the hydroxyl radical scavenging activity and β-carotene bleaching inhibition activity were increased, whereas, 2,2-azinobis (3-ethyl benzothiazoline-6-sulfonic acid) diammonium salt (ABTS+), ferric reducing antioxidant power (FRAP), metal chelating and superoxide anion scavenging activity were similar to unprocessed ones. In contrary, except dry heating in C. gladiata, all other processing methods significantly (P < 0.05) reduced the 2,2′-diphenyl-1-picryl-hydrazyl (DPPH) (20–35%), ABTS+ (22–75%), FRAP (34–74%), metal chelating (30–41%), superoxide anion radical scavenging (8–80%), hydroxyl radical scavenging (20–40%) and β-carotene bleaching inhibition activity (15–69%). In addition, the sample extracts of raw and dry heated samples protected DNA damage at 10 μg. All processing methods in E. scandens and dry heating in C. gladiata would be a suitable method for adopting in domestic or industrial processing.