Choline Chloride Based Natural Deep Eutectic Solvents as Extraction Media for Extracting Phenolic Compounds from Chokeberry (Aronia Melanocarpa)

Abstract

For the isolation of selected phenolic compounds from dried chokeberries, natural deep eutectic solvents (NADESs) were investigated as a green alternative to conventionally used extraction solvents. Four types of NADESs were synthesised, with choline chloride as the hydrogen bond acceptor in combination with different hydrogen bond donors (sugars, organic acid and urea). Ultrasound-assisted extraction was used to improve the extractability of the phenolic compounds and the results were compared to those obtained with 80% methanol as the extraction media. The highest values of total phenols and total flavonoids were found in the extract obtained with choline chloride-fructose NADES (36.15 ± 3.39 mg gallic acid g^-1 dry weight (DW) and 4.71 ± 0.33 mg rutin g^-1 DW, respectively). The extraction recoveries for the individual phenolic compounds depended strongly on the phenolic compound's structure, with relative mean values between 70% and 97%.

Keywords: HPLC; chokeberries (Aronia melanocarpa); green solvents; natural deep eutectic solvents; phenolic compounds; ultrasound-assisted extraction.

Figure 1

Total phenolic content (TPC), total flavonoid content (TFC) and total monomeric anthocyanin content (TAC) in chokeberry extracts obtained after extraction with different ChCl-LA1 aqueous solutions. TPC was expressed as mg GA g⁻¹ DW; TFC was expressed as mg RUT g⁻¹ DW; TAC was expressed as mg Cya-3-Glu g⁻¹ DW.

Figure 2

Extraction recoveries of spiked samples (%) for analysed phenolic acids ((A) and (B)-hydroxycinnamic acids; (C) and (D)-hydroxybenzoic acids; (E)-chlorogenic and rosmarinic acid) obtained after extraction with 80% MeOH and after extraction with different NADESs.

Figure 3

Extraction recoveries of spiked samples (%) for analysed flavonoids ((A)-flavones; (B)-flavonols; (C)-flavanol) obtained after extraction with 80% MeOH and after extraction with different NADESs.

Figure 4

HPLC-DAD chromatogram of standard phenolic compounds mixture (40 mg L⁻¹ of each compound) monitored at 280 nm under optimal conditions. The compounds order is listed in Table 3.