Ultrasound-assisted one-step extraction of safflower red and yellow pigments by natural ternary deep eutectic solvents: Extraction optimization and mechanism, separation and biological activities of pigments

This study explores a green and sustainable approach based on natural ternary deep eutectic Solvents (NATDES) and synergistic ultrasound-assisted extraction (UAE) of Pigments from safflower florets. Choline chloride-ethylene glycol-acetamide (ChCl-EG-AM, 1:3:1) was successfully synthesized and characterized as the most effective NATDES for the one-step extraction of safflower red and yellow Pigments. The optimal conditions for ChCl-EG-AM-UAE were as follows: solid-to-liquid ratio of 50.5 mg/mL, extraction temperature at 48 °C, extraction time of 21 min, and water content of 12.8 %. Moreover, this NATDES system could efficiently be recovered and reused in safflower Pigments extraction. Safflower Pigments also exhibit greater stability in ChCl-EG-AM under dark conditions at 4 °C. The AGREE, AGREEprep, and BAGI tools were used to evaluate this extraction process, suggestive of greenness. The Fourier transform infrared results showed that ChCl-EG-AM was mainly bonded by hydrogen bonding. Scanning electron microscope results revealed that ChCl-EG-AM disrupted the safflower florets' surface structure, facilitating the release of red and yellow Pigments. Electrostatic potential, reduced density gradient, and molecular dynamic simulations were applied to reveal the extraction mechanism of ChCl-EG-AM-UAE, which demonstrated that hydrogen-bonding interactions were the key factor underlying its high performance. The isolated Pigments (hydroxysafflor yellow A, anhydrosafflor yellow B, and carthamin) exhibit good antioxidant activity and cardioprotective effects in vitro. Overall, ultrasonic-assisted NATDES extraction is an eco-friendly method for the one-step recovery of safflower red and yellow Pigments, which reduces resource waste and simplifies the process of extraction.

Anhydrosafflor yellow B; Carthamin; Electrostatic potential; Hydroxysafflor yellow A; Natural ternary deep eutectic solvents; Safflower pigments.