Optimization of Onion Peel Bioactive Compounds Using Eco-Friendly Natural Deep Eutectic Solvent Based Ultrasound-Assisted Extraction.

The current study aimed to extract bioactive compounds from onion peel using ultrasound-assisted extraction combined with natural deep eutectic solvents. Response surface methodology (RSM) design was applied to target the maximum extract yield of bioactive compounds. The extraction (UAE-NADES) method was optimized using RSM design with varying parameters including water contents (A: 35%-55%), extraction time (B: 15-35 min), and solid-to-liquid ratio (C: 10-30 g/mL) as independent variables. Study findings showed that the highest total phenolic content (TPC) of 105.06 mg GAE/g and DPPH radical scavenging activity of 50.06 mg TE/g were observed highest at the 14th run [Conditions: Water: 35%, Extraction Time: 25 min, Solid-to-solvent ratio: 30 g/mL]. Comparison analysis of design runs also showed that factors like extraction time have a significant impact on phenolic content followed by water %. 3D response results also revealed that the set variables in the solvent mixtures significantly enhanced the extraction efficiency of phenolics and their antioxidant activities from source material (peel). Conclusively, study focused on emerging green extraction technologies for bioactive compounds recovery, gained lot of interest due to their efficiency as sustainable and environment-friendly approach and for potential use in functional/nutraceutical food industries.