Ultrasonic-Assisted\nWater-Rich Natural Deep Eutectic\nSolvents for Sustainable Polyphenol Extraction from Seaweed: A Case\nStudy on Cultivated <i>Saccharina latissima</i>

This case study introduces a green, 1 h single-step method\nusing\nwater-rich natural deep eutectic solvent (WRNADES) for ultrasound-assisted\nextraction (UAE) of polyphenols fromSaccharina latissima, a commercially cultivated brown seaweed. The extraction efficiency\nwas evaluated using a selective quantitative NMR method (s-qNMR) and\nthe traditional nonselective colorimetric total phenolic content assay\n(TPC). Initial 6 h extractions in traditional solvents (methanol,\nethanol, acetone, and ethyl acetate) showed a 40–60% increase\nin polyphenolic yields in 50% aqueous solutions measured by the TPC\nmethod. Six different water-rich (50%) NADES (WRNADES) combinations\nwere tested (choline chloride/betaine with lactic acid, citric acid,\nand 1,3-butanediol), with betaine and 1,3-butanediol (1:1) proving\nmost effective. Parameters for the WRNADES were optimized using Box–Behnken\ndesign response surface methodology, resulting in a 1:20 w/w biomass\nto solvent ratio and a 1 h extraction time at 50 °C. The WRNADES\nextraction process was refined into a scalable, single-step procedure\nand compared with traditional solvent extractions (6 h, 50% aqueous\nmethanol and acetone). A final XAD-7 polyphenol recovery step was\nincluded in all extractions. The optimized WRNADES extraction yielded\n15.97 mg GAE/g of the dry weight recovered polyphenolic extract (s-qNMR),\nexceeding the 6 h 50% aqueous methanol (12.4 mg GAE/g) and acetone\n(11.4 mg GAE/g) extractions. Thus, the UAE-WRNADES method presented\nin this case study provides a cost-effective, sustainable, and eco-friendly\nalternative for the extraction of phenolic compounds from seaweed.\nIt promotes the development of environmentally friendly production\nprocesses within the seaweed biorefinery.