Sustainable deep eutectic solvents preparation and their efficiency in extraction and enrichment of main bioactive flavonoids from sea buckthorn leaves

Deep eutectic solvents (DESs) have naturally emerged as an alternative for traditional organic solvents for their efficiency on extracting natural products from plant materials. In the present study, 12 kinds of DESs (choline chloride as the hydrogen bond acceptor) were firstly prepared and applied to extract five main flavonoids (namely rutin, quercetin-3-O-glucoside, quercetin, kaempferol and isorhamnetin) from sea buckthorn leaves (SBL) combined with microwave-assisted extraction. The results showed that the extraction efficiencies of target flavonoids by DES were significantly superior to 70% ethanol. Aiming at obtaining the optimal procedure, the extraction conditions were statistically investigated. Under the optimal conditions in pilot-scale application, the total maximum extraction yields of five main flavonoids reached to 20.820 mg/g, which was 1.321–2.400 folds to those by the traditional extraction methods. Meanwhile, the following enrichment of targets compounds from DES extraction solution exhibited excellent recoveries in the range of 72.36–84.99% were achieved by macroporous resin AB-8. In addition, the enriched flavonoids by AB-8 resin exhibited better antioxidant activities as compared with those unenriched. The results indicated that the potential of the developed method as a promising safe and sustainable alternative for selectively extraction and separation of bioactive substances from plant materials.