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Recovery of Polyphenols from the Pods of Green Gram and Black Gram and Evaluation of Their Antioxidant Activity

S. Arun, S. Deepakraj, V. Vadive and P. Brindha

Black gram (Vigna mungo L. Hepper) and green gram (Vigna radiata L. R. Wilczek) are annual herbs growing in India and contributes about 76 and 87% of total production, respectively. Black gram and green gram plays an important role in human diet as major source of vegetable proteins. Even though the nutritional value of both the legume grains were proven earlier, the health promoting compounds present in their byproducts (pods) are not yet revealed. Hence, in the present study we have focused on recovery of polyphenol compounds from black gram and green gram pods using different treatments and evaluated their antioxidant potential using in vitro models. Different extraction conditions such as solvent (ethanol) extraction with stirring, without stirring, acid hydrolysis and alkali hydrolysis at different timings were optimized. For black gram, acid hydrolysis is found to be more effective in achieving maximum yield of polyphenols (806.75 mg GAE/100 g sample) whereas alkali hydrolysis (843 mg GAE/100 g sample) was effective in the case of green gram. Extracts were analyzed for antioxidant activity, which showed higher DPPH radical scavenging action for black gram than green gram. Because, during purification in column chromatography ethyl acetate fraction of black gram showed higher concentration of total phenols. The individual phenol responsible for higher antioxidant activity of black gram pod was identified as quercetin by LC-MS method. Thus, the black gram pods could be explored as a natural source of antioxidant for the development of nutraceuticals in food industries.