Ultrasound-assisted extraction of bioactive alkaloids from Phellodendri amurensis cortex using deep eutectic solvent aqueous solutions

Deep eutectic solvents (DESs) are emerging as green and sustainable solvents for the efficient extraction of bioactive compounds. In this study, a series of DESs was prepared using choline chloride with natural, renewable organic acids, polyalcohols, or sugars. The physicochemical properties of their aqueous solutions were investigated. Subsequently, evaluation of the extraction of bioactive berberine and palmatine from a traditional Chinese herb, Phellodendri amurensis cortex (PAC), using these DES aqueous solutions was performed in an ultrasound-assisted environment. The morphologies of the raw and treated PAC samples were observed using scanning electron microscopy to determine the extraction efficiency of the ultrasonic bath using different solvents. Antioxidant capacities of PAC extract solutions were investigated by FRAP and ABTS assays. Furthermore, the extraction conditions were statistically optimized using a response surface methodology to improve the yields of the alkaloids, and the antioxidant capacities of the resultant solutions. This study demonstrates that DES aqueous solutions are suitable, green solvents for the efficient extraction of bioactive compounds from Chinese herbs with the aid of ultrasound. The use of DES aqueous solutions can eliminate the requirement of volatile organic compounds, which would reduce the damage to the environment.