Microwave-Assisted Ethanolic and Aqueous Extraction of Antioxidant Compounds from Pomegranate Peel and Broccoli Leaves By-Products

The aim of the present work was to study the effect of solvent (50%:50% ethanol:water; 100% ethanol, and 100% water) on the extraction of total phenolic content (TPC) and total antioxidant activity (TAC) from pomegranate peel and broccoli leaves by microwave-assisted extraction (MWAE). In pomegranate peel, TPC after 100% aqueous MWAE (119.6 g GAE/kg dw) increased 1.6-folder more than 100% ethanolic extraction (74.2 g GAE/kg dw). As to broccoli leaves, TPC after 100% aqueous MWAE (28.4 g GAE/kg dw) increased 3.4-folder more than 100% ethanolic extraction (8.5 g GAE/kg dw). In this sense, TAC reported a similar behavior in broccoli leaves extraction (DPPH and ABTS values ranged between 1.1-3.5 g TE/kg dw and 2.4-3.8 g TE/kg dw, respectively), while no great differences were found among solvents during the pomegranate peel extraction (DPPH and ABTS values ranged between 3.5-3.7 g TE/kg dw and 3.7-4.3 g TE/kg dw, respectively). Therefore, aqueous MWAE could be considered as green technology to recover TPC from horticultural by-products with great interest for the industry, which should contribute to the problem of food loss.