Deep eutectic solvents as green media for flavonoids extraction from the rhizomes of Polygonatum odoratum

Abstract

Recent years have witnessed the growing popularity of deep eutectic solvents (DESs) in the extraction of functional components. As a novel green alternative to organic reagents, DESs are environmentally friendly, non-toxic, inexpensive, and biodegradable. In the present study, tailor-made DESs were prepared and applied for the first time to extract flavonoids from rhizomes of Polygonatum odoratum. We also investigated the extraction process, extraction efficiency, and solvent recovery efficiency. The response surface methodology (RSM) was adopted to optimise total flavonoid extraction, and the DES was recovered through macroporous resin adsorption. The results show that the DES synthesised by choline chloride and lactic acid at a molar ratio of 1:2 was the most suitable extraction medium. Extraction conditions were optimised as follows: extraction temperature of 51 °C, DES water content of 27%, liquid–solid ratio of 22 mL/g, and extraction time of 21 min. Under these conditions, the extraction rate of total flavonoids reached 11.47 mg/g, close to that of the heat reflux extraction (HRE) with organic solvents. The adsorption and desorption experiments of flavonoids on three types of macroporous resins (HPD826, D101, and AB8) were carried out, and D101 showed higher adsorption/desorption capacities, successively followed by AB8 and HPD826. The extraction rate of the recycled DES reached 10.78 mg/g, putting the reuse rate at 93.98%. In conclusion, the developed DES combined with macroporous resin enrichment can be an alternative method for green and efficient extraction of bioactive flavonoids from plant materials.

Keywords

• Polygonatum odoratum
• Deep eutectic solvents (DESs)
• Extraction
• Flavonoids
• Response surface methodology (RSM)