Energy-Efficient Ultrasound-Assisted Extraction of Phenolic Compounds from Orange Peel Using COSMO-RS-Guided Selection of NADES

Orange peel is not waste—it's a treasure chest of antioxidants waiting for a green key. Now, scientists have found a way to unlock it using eco-friendly solvents and sound waves.

Every year, the citrus industry discards mountains of orange peel, a by-product rich in phenolic compounds and ascorbic acid. But a new study shows how to turn this waste into a source of high-value antioxidants, using a combination of natural deep eutectic solvents (NADES) and ultrasound-assisted extraction (UAE).

The researchers first used COSMOTherm solubility modeling to select six NADES, then tested them on orange peel with UAE followed by stirring. They varied sonication time (5–15 min), ultrasound power (100–400 W), and stirring time (0–45 min), measuring total phenolic content, ascorbic acid, and antioxidant capacity, while tracking energy use.

Most NADES showed a rise–plateau pattern, reaching extraction equilibrium at 20–30 minutes of stirring, while longer treatment (45 min) gave little extra benefit but consumed significantly more energy. The sweet spot was 10 minutes of UAE at 100 W followed by 40 minutes of stirring, balancing performance and sustainability.

Among the solvents, MA:Glu and LA:Glu stood out, yielding the highest concentrations of phenolic compounds and antioxidant activity. The profiles confirmed selectivity toward flavanones like hesperidin and naringin. This tailored NADES–UAE approach offers an effective, sustainable route to recover antioxidants from orange peel, supporting circular economy and green extraction technologies.

Key Points

• NADES + ultrasound extract antioxidants from orange peel efficiently.
• Optimal: 10 min UAE at 100 W plus 40 min stirring.
• MA:Glu and LA:Glu best for phenolics and antioxidant activity.