Biochemical Studies on Antioxidant Potential of Green Beans in Fresh and Processed Conditions

The present study was undertaken to evaluate the total antioxidant potential of four different varieties of green beans namely Phaseolus vulgaris (french beans), Vicia faba (broad beans), Cyamopsis tetragonoloba (cluster beans) and Vigna unguiculata (cowpea beans) in both fresh and processed condition (microwave assisted). The total phenolic and flavonoid contents were determined by Folin Coilteaus and AlCl3 assay respectively. The antioxidant activity was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, hydrogen peroxide(H2O2) decomposition and reducing power assay. Efforts were also made to study the interaction of beans with metal ions. Total phenolic content ranged from 105.00 ± 0.021 to 300.00 ± 0.009 µg GAE.g-1  (Gallic acid equivalent) of extract and flavonoid content ranged from 55.00 ± 0.017 to 550.00 ± 0.050 µg QE.g-1 (Quercitin equivalent) of extract. All the extracts scavenged DPPH radical and decomposed H2O2. The reducing potential was found to be highest in Cyamopsis tetragonoloba followed by Vigna unguiculata, Vicia faba and Phaseolus vulgaris. Good correlation of phenolic content was observed with reducing power ability ( r2 = 0.743) and DPPH radical scavenging property (r2 = 0.694). The extracts chelated both the ionic forms of iron Fe2+ and Fe3+ but the affinity towards Fe3+ was higher. Green beans can be considered as a potential source of antioxidants. Fresh extracts were found to have higher antioxidant potential as compared to processed extracts.