A Novel Ethanolic Two-Phase System Based on Deep Eutectic Solvents and Amphiphilic Copolymer for the Extraction of Neohesperidin and Naringin from the Pomelo Peel

A novel ethanolic two-phase system (ETPS) composed of Pluronic(®)L-64 (PL 64) and deep eutectic solvents (DESs) was constructed for the separation of two similar flavonoids of naringin (Nar) and neohesperidin (Neo) from the pomelo peel. The selectivity (S) data showed that DES prepared from tetrabutylammonium bromide (N(4444)Br) and glycerol (Gly) had the optimal distribution efficiency for Nar and Neo standards. A binodal curve of N(4444)Br-Gly/PL 64/ethanol system fitted to the nonlinear Merchuk relationship showed that the biphasic region was narrow for ETPS. The influences of the mass ratio of DESs and PL 64, DES concentration, PL 64 concentration, molar ratio of DESs, temperature, phosphate buffer solution, and ethanolic pH were studied in single-factor experiments. Under the optimal conditions, the maximum extraction efficiency (E(Nar) = 68.32%, E(Neo) = 86.09%), partition coefficient (K(Nar) = 6.66, K(Neo) = 19.13), and S (2.88) were obtained in the DESs-rich (bottom) phase. N(4444)Br-Gly, Nar, and Neo with recovery yields of 78.12%, 66.61%, and 68.03%, respectively, had been recovered using D101 macroporous resin. This proposed ETPS is efficient and environmentally friendly and is expected to avail meaningful references for the separation of natural products with similar structures.