Biphasic Eutectic Systems for the Simultaneous Recovery of Carotenoids and Polyphenols From Mango Peel

This study introduces biphasic eutectic systems combining hydrophobic (menthol:lauric acid, MLAU) and hydrophilic deep eutectic solvents (DESs) for the simultaneous, single-step recovery of carotenoids and polyphenols from mango peel (MCP), a major agri-food by-product. Four biphasic systems were formulated and characterised by dye partitioning, Fourier transform infrared (FT-IR), and 1H nuclear magnetic resonance (NMR), confirming phase immiscibility and structural integrity in three systems after mixing. Extraction experiments at varying solid-to-solvent ratios (1:15–1:60) demonstrated significantly higher yields than conventional organic solvents: the top (hydrophobic) phase enriched in carotenoids (up to 3.8 µg β-carotene/mg DW), while the bottom (hydrophilic) phase preferentially recovered polyphenols (up to 1.9-fold for mangiferin and quercetin-3-O-galactoside). The MLAU/β-alanine:malic acid:water (1:1:3) system at a 1:30 ratio gave the best simultaneous performance. Semi-empirical PM6 calculations coupled with quantum theory of atoms in molecules (QTAIM) and non–covalent interaction (NCI) analyses elucidated governing interactions: weak C-H···π and H···H contacts dominate carotenoid solubilisation in the hydrophobic phase, while an extensive hydrogen-bonding network drives polyphenol partitioning into the hydrophilic phase. These tuneable biphasic DESs offer a sustainable, efficient platform for valorising mango peel waste into high-value bioactive compounds.