Green approach to extract bioactive compounds from orange peel employing hydrophilic and hydrophobic deep eutectic solvents

Consumer interest in natural products with advantageous biological impacts on their health has increased in recent years. Therefore, academic and industrial communities have concentrated their research on developing sustainable techniques for extracting bioactive compounds from natural resources. In the present study, extracts rich in bioactive compounds from orange peel were obtained using novel hydrophilic and hydrophobic deep eutectic solvents (DESs). Bioactive compounds such as carotenoids and polyphenols, their stability, antioxidant capacity, permeability, and biological activity were determined to consider their inclusion in food formulations. The results demonstrated that the highest total carotenoid values were obtained with hydrophobic DESs using DL-Menthol: camphor (163.5 ± 1.1 mg/100g_fw), DL-Menthol: Eucalyptol (168.7 ± 1.7mg/100g_fw), and lauric acid: octanoic acid (153.1 ± 7.1 mg/100g_fw). Total polyphenols were higher in hydrophilic DESs such as proline: malic acid (282.8 ± 7.3 mg/100g_fw). The antioxidant values showed that hydrophobic extracts have higher antioxidant activity than traditional solvents. Carotenoid stability was also improved using DL-Menthol: camphor, while lactic acid: glucose and proline: malic acid showed a better capacity to stabilize polyphenols. To simulate carotenoid and polyphenol permeation, the Parallel Artificial Membrane Permeability Assay (PAMPA) was used and demonstrated that DESs can enhance the permeability of these bioactive compounds. Biological tests were also performed, and the antiproliferative effect in HeLa cells showed only 26.70% cell viability in DL-Menthol: camphor extracts. Based on the presented results, DESs can be used to extract hydrophilic and hydrophobic compounds from orange peels, and the obtained extracts could be included in food formulations, avoiding the solvent elimination process.