Ultrasound-assisted extraction of major anthocyanins in Korean black raspberries (Rubus coreanus Miquel) using natural deep eutectic solvents

This study investigated a methodology for the extraction of major anthocyanin from Korean black raspberries (KBR) using green chemistry. Ternary natural deep eutectic solvent (NADES) used in this study consisted of choline chloride, malic acid, and 1,4-butanediol (2:1:1; w/w/w) based on the viscosity and total anthocyanin contents. The interaction between the components of ternary NADES and their characteristic functional groups were confirmed from infrared spectroscopy. The optimized extraction conditions based on the Box–Behnken design and response surface methodology were as follows: extraction temperature of 26.6 °C, extraction time of 15.2 min, and NADESs water content of 23.3% (v/v). The efficient extraction efficiency and storage stability of cyanidin-3-O-glucoside (C3G) in the ternary NADES were determined. The extraction efficiency of C3G from KBR was most influenced by the water content of the NADES. The storage stability of C3G extracted from KBR using the ultrasound-assisted method with optimized ternary NADES was higher than pure water and acidic water (0.1M HCl). C3G from KBR in the NADES remained stable at > 97% for nine days. The proposed methodology adheres to green chemistry principles, emphasizing on low energy consumption, mild conditions, biodegradability, and eco-friendliness.