Sustainable ultrasound-assisted extraction of polyphenols from Cinnamomum cassia bark using hydrophilic natural deep eutectic solvents

Natural Deep Eutectic Solvent (NADES) is a new category of green solvent that is environmentally friendly and efficient, which can be a substitute of conventional extraction solvent. In the current study, the hydrogen bonding formation in NADES was identified using Fourier-transform infrared spectroscopy. The extraction efficiency of twelve NADESs was screened. The combination of choline chloride and levulinic acid (NADES 9) at a molar ratio of 1:2 showed the highest extraction yield of cinnamic acid and cinnamaldehyde from the Cinnamomum cassia bark compared to other NADESs, ethanol and water. Based on the One-Factor-At-a-Time experiment, the extraction conditions were optimized by response surface methodology using the Box-Behnken design. The optimum extraction conditions were 26% water content in NADES 9, extraction time of 22 min, solvent-tosolid ratio of 15 mL/g, and ultrasonic power of 160 W. Under the optimum extraction conditions, the extraction yields of cinnamic acid and cinnamaldehyde were around 0.5714-0.5979 mg/g and 26.2722-27.1490 mg/g, respectively. The validation of experimental and predicted results under optimum conditions demonstrated good agreement. The morphology analysis of C. cassia powder after extraction showed that the application of NADES 9 enhanced the pore formation compared to ethanol.