Efficient Extraction of Flavonoids from Lotus Leaves by Ultrasonic-Assisted Deep Eutectic Solvent Extraction and Its Evaluation on Antioxidant Activities

Abstract

The discovery of a green extraction solvent for natural plants could promote related research. In this study, deep eutectic solvents (DES) were used as green solvents coupled with an ultrasound-assisted extraction method (UAE) to extract flavonoids from lotus leaves. Thirty-four different DES were performed and choline chloride/urea with 40% water was chosen as the most promising one, and the related parameters in the procedures were optimized, resulting in the highest extraction amount of flavonoids in lotus leaves. D-101 was selected from four macroporous resins to separate the flavonoids from DES. Moreover, DES could be recycled and efficiently reused four times with satisfactory performances. In addition, the lotus leaf flavonoids from the DES extract exhibited antioxidant activities in five kinds of assays including DPPH, ABTS, Fe3+ reducing, FRAP, and Fe2+ chelating. It also showed antibacterial activities on Staphylococcus aureus and Escherichia coli bacterial strains with minimal inhibitory concentrations at 1666 μg/mL and 208 μg/mL, respectively. In the HPLC analysis, the three main components in the DES extract were identified as astragalin, hyperoside, and isoquercitrin. In conclusion, the developed UAE-DES followed by macroporous resin treatment could become an efficient and environmentally friendly extraction and enrichment method for flavonoids from lotus leaves and other natural products.

Comparison of the Efficiency of Deep Eutectic and Organic Solvents in the Extraction of Phytochemicals from Cannabis sativa L.

“…The results revealed that DESs based on choline chloride (choline chloride/ethylene glycol and choline chloride/urea) extracted a higher amount of CBD, 0.87% and 0.78%, respectively, than ethanol (0.69%), the organic solvent most used in hemp extraction. These findings are consistent with those of Liu et al [23] in which DESs with choline chloride/urea extracted the highest amount of flavonoids from lotus leaves. However, these findings are contrary to those of Tiago et al, in which they observed a large amount of CBD extracted using menthol/lauric acid [19].…”

Deep eutectic solvent-ultrasound assisted extraction as a green approach for enhanced extraction of naringenin from Searsia tripartita and retained their bioactivities

“…Increasing the water ratio in DES-1 from 20 to 50% led to an important improvement in the extraction yield of NA. The high extraction yield may have been achieved because DES-1 viscosity and polarity were optimized by adding water, resulting in more effective interactions between ST and DES-1 ( 43 , 44 ). Yet, the extraction efficiency dropped dramatically when the water content was brought up to 50%.…”

“…As discussed earlier, the molar ratio of HBD to HBA in the DES controls the hydrogen bonding interaction, which affects the viscosity and surface tension of DES (43). As a result, optimizing the mass transfer rate and processing efficiency relies on selecting appropriate water content in DES.…”