Modelling and optimization of natural deep eutectic solvent-assisted extraction for carotenoids targeting lutein for developing food additives from used marigold flowers

Natural deep eutectic solvents (NADES) have proved their potential as a green technology for extracting phytochemicals in recent times. Different NADES combinations with various molar ratios of choline chloride as a hydrogen bond acceptor (HBA) and glucose/tartaric acid as a hydrogen bond donor (HBD) were screened for better extraction efficiency of carotenoids from a rich source-dried marigold flower. The highest carotenoid content of 549.68 μg/mg dry weight (DW) was observed in choline chloride: glucose (3:1) combination. Process optimization using Taguchi’s model and response surface methodology (Box-Behnken design) was further employed to identify the optimal process parameters, viz., ultrasonication time as 35 min, incubation temperature as 25°C, and incubation time as two hours; a significant increase in carotenoid yield of 971.31 μg/mg DW of floral biomass was observed. Stability studies showed that carotenoids were stable in the dark and at a storage temperature of -20 °C. High performance liquid chromatography analysis revealed the presence of lutein as a major compound in the selected NADES system. Lastly, food safety studies of marigold floral NADES-based extracts were investigated. Antimicrobial and antioxidant activity studies of selected extracts revealed optimal properties indicating their potential to be formulated into food colorants and nutraceuticals. • Choline chloride-glucose (3:1) significantly yield higher carotenoids • Extraction process optimization via Taguchi and Box-Behnken design was carried out. • HPLC confirmed presence of lutein in the NADES-based extracts. • Stability and food safety studies indicated potential food additive formulation.