Efficient extraction of bioactive flavonoids from Celtis sinensis leaves using deep eutectic solvent as green media

Deep eutectic solvent extraction of myricetin and antioxidant properties

In this study, a response surface method (RSM) was used to optimise the ultrasonic-assisted deep eutectic solvent (DES) extraction of myricetin from myricetin leaves. The results demonstrated that the DES-5 (choline chloride-oxalic acid) system exhibited better extraction results than the other seven DESs prepared. The optimum extraction conditions for myricetin were a DES-5 system with 19% water content of DES, a liquid-to-solid ratio of 37 : 1 mL g-1, an extraction time of 45 min, and an extraction temperature of 72 °C. Under these conditions, the extraction amount of myricetin was 22.47 mg g-1. To optimise the extraction process, the crude myricetin extract was purified, and the optimal conditions were as follows: an AB-8 macroporous adsorption resin was used with an anhydrous ethanol desorption agent. The adsorption rate was 1 BV per h (bed volume per hour), the desorption rate was 1 BV per h, and the desorption capacity was 2 BV (bed volume). The antioxidant properties of the myricetin were also investigated. The results demonstrated that, with an increase in concentration, the scavenging rates of DPPH and ˙OH free radicals increased. Compared to Vc, myricetin had a better scavenging ability for DPPH free radicals, whereas purified myricetin had a better antioxidant effect. At the same concentration, the radical-scavenging rate of the ˙OH radical was slightly higher in myricetin purified by the macroporous adsorption resin than in Vc, and that of the unpurified myricetin was the smallest. Myricetin was purified using a macroporous adsorption resin to improve its antioxidant properties.

High-voltage pulse-assisted extraction of flavonoids from kapok using deep eutectic solvent aqueous solutions

In this study, deep eutectic solvents coupled with a pulsed electric field (PEF-DES) were first applied to the extraction of traditional Chinese medicine plants. This study uses the PEF-DES extraction technique to extract TG-KF (Kapok flavonoid solution extracted with DES-TG). PEF-DES is a simple, effective and environmentally-friendly technology and can be used in industrial-scale production. For the optimal extraction conditions of TG-KF, DES-TG was used as a solvent, the DES-TG concentration was 50%, the solid-liquid ratio was 1 : 30, the electric field intensity was 0.55 kV cm-1, the number of pulses was 100, and the yield of flavonoids was 14.36 ± 0.35%. TG-KF has very good stability and there is no precipitation or discoloration within 6 months. The results of chicken embryo experiments and human patch tests show that 10% TG-KF aqueous solution has no irritation. DPPH experiments show that TG-KF has excellent efficacy as an antioxidant. Overall, TG-KF is expected to become a potential antioxidant raw material.