Exploring the impact of choline chloride based deep eutectic solvents' presence in the recovery process of phenolic antioxidants from Moringa oleifera leaves: A multivariate optimization study and principal component analysis

Considering the environmental concerns of the organic solvents (non-sustainability, easy flammability, low biodegradability, toxicity and volatility), deep eutectic solvent (DES) has been emerged as green solvent for sustainable chemistry and engineering. Different from the reported studies on the extraction of bioactives from Moringa oleifera leaves, choline chloride based DESs (13 combinations) were designed with several ratios in this study. 6 polyols (1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, glycerol and ethylene glycol), 2 sugars (D-glucose and D-fructose), 4 acids (malic acid, malonic acid, levulinic acid and citric acid) and urea were used as hydrogen bond donor (HBD), while choline chloride (ChCl) was HBA. After determination of the best combination (ChCl/1,4-butanediol) for the highest total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity (AA) yields, the optimization of the extraction system was performed by Box-Behnken design (BBD) under Response Surface Method (RSM). The pulsed ultrasonic-assisted extraction process with 3 factors (amplitude, water addition into the DES and extraction time) and 3 levels was designed by Box-Behnken design. The goal was to maximize the TPC, TFC, AA and p-coumaric acid (the principal phenolic compound) of the extract. The best DES combination was also supported by chemometric analyses by application of principal component analysis (PCA).