Experimental study demonstrates efficient ultrasonic extraction of quercetin from onion peel using deep eutectic solvents, highlighting sustainable agricultural waste valorization.
Key Points
To develop and optimize an ultrasound-assisted deep eutectic solvent extraction method for recovering quercetin from onion peel and determine the underlying extraction mechanisms.
Screened deep eutectic solvent systems and optimized extraction parameters (temperature, time, water content, liquid–solid ratio, and ultrasonic power) using single-factor tests and a Box–Behnken design.
Identified phenolic compounds via LC-MS, purified extracts with C18 reversed-phase solid-phase extraction, and examined extraction mechanisms using quantum chemistry and molecular dynamics simulations.
Optimal extraction with betaine-malonic acid yielded 21.83 mg/g quercetin, 30.27 mg RE/g flavonoids, and 77.33 mg GAE/g polyphenols under 376.26 W ultrasonic power at 50 °C for 40 min.
LC-MS identified quercetin monoglucoside as the predominant flavonoid, and subsequent C18 purification markedly enhanced DPPH and ABTS radical scavenging activity.
Simulations showed that hydrogen bonding, electrostatic complementarity, and van der Waals interactions collectively drove flavonoid desorption and solvation.