Extraction of Phenolic Compounds from Agro-Industrial By-Products Using Natural Deep Eutectic Solvents: A Review of Green and Advanced Techniques

What if the secret to greener chemistry was hiding in food waste? A new review shows how natural deep eutectic solvents can turn agricultural leftovers into treasure troves of antioxidants.

The circular economy is turning trash into treasure, and agri-food by-products are the latest goldmine. These leftovers are packed with phenolic compounds—molecules with antioxidant and anti-inflammatory powers. But traditional extraction methods rely on organic solvents, which clash with green chemistry ideals. Enter natural deep eutectic solvents (NaDESs): eco-friendly alternatives that dissolve bioactive compounds without the environmental guilt.

A recent review sifted through studies from 2020 to 2024, focusing on three assisted techniques: ultrasound, microwave, and pressurized liquid extraction. Of 116 initial papers, only 19 met the strict criteria. The findings? Ultrasound combined with NaDESs worked wonders, especially for fruit and oilseed residues. Microwave extraction delivered high yields of phenolic acids and flavonoids, though it stumbled at high temperatures. Pressurized liquid extraction, still under-explored, showed promise when fine-tuned for temperature, pressure, and solvent mix.

Together, these methods boost yield, selectivity, and environmental performance compared to conventional approaches. This isn't just lab talk—it's a blueprint for a biorefinery that turns waste into functional ingredients. By embracing NaDESs, we can clean up both our plates and the planet, one sustainable extraction at a time.

Key Points

• NaDESs are green alternatives to organic solvents for phenolic extraction.
• Ultrasound with NaDESs excels for fruit and oilseed residues.
• Microwave and pressurized methods show promise but need optimization.