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

What if the secret to safer food colorants was hiding in discarded marigold flowers? Scientists just turned this waste into a treasure trove of natural pigments using green chemistry.

Marigold flowers, often tossed aside after their ornamental life, are packed with carotenoids—natural pigments that could replace synthetic dyes linked to health issues in children and adults. But extracting these compounds usually requires harsh solvents. Enter natural deep eutectic solvents (NADES), a green alternative that mimics nature's own chemistry.

Researchers screened combinations of choline chloride with glucose or tartaric acid as hydrogen bond donors. The winning pair—choline chloride and glucose in a 3:1 ratio—yielded 549.68 μg of carotenoids per milligram of dried flower weight. Then, using Taguchi's model and response surface methodology, they fine-tuned the process: 35 minutes of ultrasonication, incubation at 25°C for 2 hours. The optimized conditions boosted the yield to 971.31 μg/mg dry weight—a significant jump.

The extracted carotenoids stayed stable in the dark at −20°C, and HPLC analysis revealed lutein as the star compound. Further tests showed the extracts had promising antioxidant and antimicrobial properties, making them safe candidates for food colorants and nutraceuticals. This approach not only valorizes waste but also offers a healthier alternative to synthetic additives.

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