September 29, 2025

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

Puntos clave

NADES11 exhibited the highest total flavonoid content, significantly outperforming ethanol extraction methods.
Under optimal extraction conditions of 97 min, 64 °C, and 1:25 solvent-to-material ratio, higher antioxidant activities were recorded.
Thirteen formulations of NADES were tested, with NADES11 consisting of lactic acid, citric acid, and glycerol yielding the best results.
The study employs response surface methodology and central composite design for systematic optimization of the extraction process.

Resumen

Natural Deep Eutectic Solvents (NADES) have emerged as promising, environmentally friendly alternatives to conventional organic solvents for the extraction of bioactive compounds. However, their application to Erythrina crista-galli, a species known for its rich flavonoid content and therapeutic potential, has not yet been systematically investigated. This study addresses this research gap by developing an ultrasound-assisted extraction (UAE) process using NADES, statistically optimized through Central Composite Design (CCD). Among thirteen NADES formulations tested, the NADES11 formulation, composed of lactic acid, citric acid, and glycerol in a molar ratio of 4.5:4.5:1, demonstrated the highest total flavonoid content (TFC) and was selected for further optimization using Response Surface Methodology (RSM). The optimal extraction conditions were established at 97 min, 64 °C, and a solvent-to-material ratio of 1:25. Under these optimized parameters, the antioxidant activities of NADES11 and ethanol extracts were evaluated using DPPH, ABTS, and FRAP assays. The NADES11 extract exhibited significantly higher antioxidant activities, with values of 0.3690 ± 0.0039, 0.2965 ± 0.0118 mmol Trolox/g, and 0.6095 ± 0.0059 mmol Fe²⁺/g, respectively, compared to the ethanol extract, which yielded 0.0532 ± 0.0022, 0.0439 ± 0.0009 mmol Trolox/g, and 0.1043 ± 0.0018 mmol Fe²⁺/g. These results confirm the superior capability of NADES11 not only in efficiently extracting flavonoid compounds but also in preserving their antioxidant properties. HIGHLIGHTS This study explores natural deep eutectic solvents (NADES) as eco-friendly alternatives to conventional solvents for extracting flavonoids from crista-galli twigs. Thirteen NADES formulations were tested, with NADES-11 comprising od lactic acid, citric acid, and glycerol with a ratio of 4.5:4.5:1 showing the highest flavonoid yield. NADES-based extraction was combined with Ultrasound-Assisted Extraction (UAE) to improve efficiency. Extraction parameters were optimized using Response Surface Methodology (RSM) and Central Composite Design (CCD), yielding optimal conditions at 97 min, 64 °C, and a 1:25 solvent-to-material ratio. NADES-11 extract exhibited significantly higher antioxidant activity (DPPH, ABTS, and FRAP assays) compared to the ethanol extract. This work represents the first systematic and statistically optimized NADES-UAE protocol for flavonoid extraction from crista-galli, highlighting its potential as a sustainable green extraction strategy. GRAPHICAL ABSTRACT

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