Optimization of ultrasound- and enzymatic-assisted extractions of polyphenols from dried red onion peels and evaluation of their antioxidant activities.

There is a recognized need for exploring new natural antioxidants that have high antioxidant potential. Thus, the aim of this study was to optimize the extraction process of onion peels using ultrasound- and enzymatic-assisted extractions (UAE and EAE) methods to utilize the optimal extracts as natural antioxidants. Box-Behnken Design (BBD) was implemented to reach the optimal extracts with the highest simultaneous content of total phenolic content (TPC) and total flavonoid content (TFC).