Hydrophobic eutectic solvents for sustainable recovery of carotenoids from mango peel: Extraction optimization and insights into molecular interactions at play

Mango peel, one of the main by-products of the mango processing industry, is emerging as a valuable source of bioactive compounds, particularly carotenoids. However, efficient extraction and preservation of these compounds remain challenging. This study explored the potential of hydrophobic eutectic solvents (HESs) for extracting carotenoids from mango criollo peels. Several HESs demonstrated enhanced extraction efficiency and improved carotenoid stability under light and thermal stress conditions compared to conventional solvents. Response surface methodology was employed to optimize the extraction process using a thymol-menthol-based HES, resulting in a significant increase in carotenoid yield. The optimized extract had a higher light stability, maintaining 87 % of its initial antioxidant activity after 480 min of UV-A exposure. The most abundant carotenoids in the optimized extract evaluated by HPLC-DAD were β-carotene and lutein. A theoretical study using density functional theory (DFT) and Quantum Theory of Atoms in Molecules (QTAIM) was performed to elucidate the interactions between β-carotene and thymol-menthol complexes. Weak interactions create multiple contact points between β-carotene and thymol-menthol, which are crucial for both the extraction process and complex stabilization. Additionally, the electron density of intermolecular interactions has been demonstrated to be a reliable indicator of stability, making it a valuable parameter for designing novel eutectic solvents.