Ultrasound-Assisted Extraction of Flavonoids from Erythrina crista-galli Twigs Using Natural Deep Eutectic Solvents: Process Optimization and Antioxidant Evaluation

What if the key to unlocking nature's antioxidants lies in a solvent made from everyday acids and sugars? A new study reveals that a natural deep eutectic solvent can outperform traditional ethanol in extracting flavonoids from a medicinal tree.

Natural Deep Eutectic Solvents (NADES) are emerging as green heroes in the lab, replacing harsh organic solvents with mixtures of natural compounds. But until now, their power had not been tested on Erythrina crista-galli, a tree rich in flavonoids with therapeutic promise. This study dives into that gap, using ultrasound-assisted extraction (UAE) to coax out these bioactive molecules efficiently.

Among thirteen NADES formulations, one stood out: NADES11, a blend of lactic acid, citric acid, and glycerol in a 4.5:4.5:1 molar ratio. It delivered the highest total flavonoid content, and the team optimized the process using statistical design. The sweet spot: 97 minutes, 64°C, and a solvent-to-material ratio of 1:25.

When comparing antioxidant activity, NADES11 blew ethanol out of the water. In DPPH, ABTS, and FRAP assays, NADES11 extracts showed significantly higher values—0.3690, 0.2965 mmol Trolox/g, and 0.6095 mmol Fe²⁺/g—versus ethanol's 0.0532, 0.0439, and 0.1043. This confirms that NADES not only extracts more flavonoids but also preserves their antioxidant punch, offering a greener, more effective path for nutraceutical and pharmaceutical applications.

Key Points

• NADES11 (lactic acid, citric acid, glycerol) gave highest flavonoid yield.
• Optimal UAE: 97 min, 64°C, solvent ratio 1:25.
• NADES11 extract showed up to 7x higher antioxidant activity than ethanol.