Greener extraction of anthocyanins and antioxidant activity from blackberry (Rubus spp) using natural deep eutectic solvents

Abstract

Natural deep eutectic solvents (NaDESs) are new green solvents used for the extraction of phenolic compounds. In this work, an efficient and greener strategy for extracting blackberry anthocyanins using NADESs was investigated. Sixteen NADESs constituted of choline chloride-urea, choline chloride-sugars, choline chloride-organic acids, choline chloride-polyalcohols and organic acids-sugars were synthesized. The antioxidant properties and anthocyanin profile of blackberry extracts obtained with NADESs and conventional solvents (water, methanol and ethanol)were evaluated. Results of the characterization of NADESs showed that the viscosity, pH, electric conductivity and chemical structure of NADESs were greatly influenced by the hydrogen bond acceptors and hydrogen bond donors. The highest recovery efficiencies were recorded with NADESs giving the highest total phenolic content (9.35 ± 0.39 mg GAE/G), total flavonoid content (104.72 ± 5.17 mg ECE/100g), total anthocyanin content (115.37 ± 0.43), antiradical activity (68.77 ± 2.29 mmol TE/g), reducing power (83.08 ± 3.78) and metal chelating activity (4771.25 ± 83.58 mg TE/100g). NADESs were the most prominent solvents for the recovery of the targeted anthocyanins, with the more acidic NADESs extracting higher quantities of cyanidin-3-glucoside, cyanidin-3-rutinoside, cyanidin chloride and pelargonidin-3-glucoside. A greener extraction using NADES can therefore effectively and reliably targets antioxidants and particularly anthocyanins in blackberry, offering promising ways for future investigations on the phytochemicals in plants.