Evaluation of Total Phenol and Flavonoid Content, Antioxidant and Iron Chelation Activities of Ethanolic Extracts of Green Beans

Green beans contain high concentration of polyphenols, carotenoids, ascorbic acids, tocopherol and flavonoids which fight against oxidative damage. Free radicals have been implicated in the pathogenesis of most diseases. Thus, the consumption of dietary antioxidants from vegetables and fruits is beneficial in preventing these diseases. The present study was undertaken to evaluate antioxidant potential of ethanolic extracts of four different species of green beans. Ethanolic extract of Phaseolus vulgaris (french bean), Vicia faba (broad bean), Cyamopsis tetragonoloba (cluster bean) and Vigna unguiculata (cowpea) were studied for antioxidant properties by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay, H2O2 decomposition, reducing power ability assay. Total phenolic content was measured by Folin Coilteau reaction and flavonoid contents were determined by AlCl3 assay. Efforts were made to study the iron chelation. Total phenol content ranged from 17.00 ± 0.004 to 53± 0.007 µg GAE/mg while total flavonoid ranged 22 ± 0.003 to 36 ± 0.006 µg QE/ mg. All the extracts scavenged DPPH radical, decomposed H2O2 and had significant reducing potential. The IC50 for DPPH scavenging activity was highest for Vigna unguiculata as 2.27 ± 0.19 mg/ml while lowest for Vicia faba as 0.18± 0.02 mg/ml. All the extracts chelated Fe2+ form of iron but not Fe3+. A positive and strong correlation (r2 = 0.9) between total phenolic content & antioxidant activity suggests that green beans have enormous potential to enhance antioxidant capacity of our daily food supply and may provide health benefits in oxidative stress as neutraceuticals.