Ultrasonic-assisted Extraction of Flavonoids and Polyphenols from Clerodendranthus spicatus by Deep Eutectic Solvents and Its Antioxidant Activity

Purpose To optimize the extraction of flavonoids and polyphenols from Clerodendranthus spicatus by ultrasonic-assisted deep eutectic solvents (DESs), evaluating its antioxidant activity.

Methods The DES with the highest yield of flavonoids and polyphenols from C. spicatus were screened among six kinds of DESs. Then, single-factor tests and response surface Box-Behnken design test were used to optimize the extraction of flavonoids and polyphenols from C. spicatus by ultrasounds-assisted DES, and the DPPH· scavenging ability, ABTS⁺ scavenging ability and reducing ability of extracts were determined.

Results The results of single-factor tests showed that the optimal extraction conditions for extracting flavonoids and polyphenols from C. spicatus were determined, including that n_{choline chloride}∶n_{ethylene glycol} was 1∶5, the water content was 30%, the ratio of solid to liquid was 1∶20 (g∶mL), the extraction temperature was 70 ℃, and the extraction time was 40 min. The experimental results of response surface Box-Behnken design test showed that the yield of flavonoids was 140.87 mg/g and the yield of polyphenols was 63.58 mg/g, with the extraction conditions that n_{choline chloride}∶n_{ethylene glycol} was 1∶5, the water content was 30%, the ratio of solid to liquid was 1∶21 (g∶mL), the extraction temperature was 67 ℃, and the extraction time was 42 min, which were significantly higher than that of 50% ethanol. The DPPH· scavenging ability, ABTS⁺ scavenging ability and reducing ability of extracts by DES were higher than that of the extract by 50% ethanol.

Conclusion The DESs can be used as new type of solvent to eco-friendly and efficiently extract flavonoids and polyphenols from C. spicatus, which can provide basic technical support for the deep development of C. spicatus.