Sustainable valorization of functional phytochemicals from Polygonum multiflorum using natural deep eutectic solvents (NADES)

This study applied a natural deep eutectic solvent (NADES) consisting of malic acid and choline chloride for bioactive compound extraction from Reynoutria multiflora (Thunb.) Moldenke (syn. Polygonum multiflorum thunb ), an important medicinal and agricultural resource. Optimization with 10 % water addition yielded a 90 % NADES system that significantly improved viscosity and mass transfer. The optimized extract provided higher or comparable yields of 2,3,5,4′-tetrahydroxystilbene-2-O-β- D -glucoside (THSG), emodin, and physcion compared with hot water or 70 % ethanol extracts. It also showed the highest enrichment of polymeric tannins and exhibited superior antioxidant capacity across multiple assays. GC/MS-based profiling and PLS-DA revealed a distinct volatile spectrum, while the extract demonstrated strong lipid peroxidation inhibition and COX-2 suppression, indicating its multifunctional bioactivity. Beyond laboratory performance, this approach emphasizes industrial relevance. The use of food compatible NADES offers a biodegradable, safe, and industrially viable alternative to conventional solvents for efficient extraction of bioactive compounds. The enhanced phytochemical recovery and multifunctional activities highlight the potential of P. multiflorum as a renewable crop resource for high-value applications in functional foods, nutraceuticals, pharmaceuticals, and natural preservatives. Furthermore, the strategy may be extended to other underutilized crops and agricultural by-products, promoting circular economy practices and adding value to medicinal plant resources. • A food-grade malic acid–choline chloride DES was optimized for bioactive extraction. • The 90 % MAL/CHO extract showed superior THSG, emodin, and physcion yields. • DES extract had the highest antioxidant activity in TRC, DPPH, and FRAP assays. • Volatile profile of the DES extract was distinct and rich in pyrazines and ketones. • DES extract exhibited the strongest COX-2 inhibition among all tested solvents.