Green extraction of flavonoids and phenolic acids from elderberry (Sambucus nigra L.) and rosemary (Rosmarinus officinalis L.) using deep eutectic solvents

Recent research on the extraction of valuable natural compounds, especially plants antioxidants, was focused on the use of green solvents, including deep eutectic solvents (DES). In this paper, for the first time, selected DES solvents were applied for the extraction of phenolic acids and flavonoids from elderberry (Sambucus nigra L.) and rosemary (Rosmarinus officinalis L.). The presence of those polyphenolic compounds in elderberry flowers and rosemary leaves was detected by thin-layer chromatography, and their contents were determined spectrophotometrically. Extraction efficiencies of water, 70% ethanol and DESs based on choline chloride (ChCl) and ethylene glycol (EG) in a molar ratio of 1:3 and choline chloride and glycerol (Gly) in the same molar ratio were compared. DESs were applied in pure form and with the addition of 30% and 50% of water (V/V). Obtained results showed that 50% ChCl:Gly and 50% ChCl:EG have similar efficiency for phenolic acid extraction as commonly used 70% ethanol. The EG-based DES showed slightly higher performance for the extraction of rosemary phenolic acids, while the one based on Gly showed better results for elderberry. With respect to flavonoid extraction from elderberry flowers, 70% ChCl:EG was comparable to 70% ethanol. Our study demonstrated that tested novel and environmentally friendly DESs could replace ethanol for the extraction of plant polyphenols.