Antioxidant activity and mechanism exploration for microwave-assisted extraction of flavonoids from Scutellariae Radix using natural deep eutectic solvent

In this work, a natural deep eutectic solvent combined with microwave-assisted extraction (NADES-MAE) was studied and effectively utilized for the simultaneous extraction of the flavonoids from Scutellaria baicalensis. NADES composed of L-proline and urea were selected to achieve the efficient extraction of baicalin, baicalein, and wogonin. Box Behnken design (BBD) was applied to optimize the extraction conditions. The optimum conditions were as follows: L-proline and urea with a molar ratio of 2:1, water content of 40 %, extraction temperature of 110 °C, extraction time of 20 min, and liquid–solid ratio of 40 mL/g. Compared with the traditional extraction method, NADES-MAE displays the merits of higher yield, shorter extraction time, and less organic solvent consumption. In addition, the as-prepared NADES was characterized by FTIR and 1H NMR, and the extraction mechanism for the flavonoids was investigated by density functional theory. The outcomes of biological activities in vitro showed that the extracts revealed desirable antioxidant activity. After assessing the ecological impact, the cytotoxicity of NADES was investigated and the results displayed that toxicity of the NADES was very low or even negligible with EC50 > 2000 mg/L. The results indicated that the suggested approach was sensitive, green, and simple, showing good potential for analysis of active components from natural sources.