Repurposing orange peel waste for limonene extraction using deep eutectic solvents for cosmetic applications

Orange peel waste, a byproduct of the citrus industry, can be valorized to obtain valuable compounds such as limonene, a terpene widely used in the food and cosmetics industry for its characteristic citrus aroma. Conventional extraction methods rely on organic solvents, which pose significant environmental concerns. To address this, deep eutectic solvents ( D ES) have emerged as a sustainable alternative. In this work, we screened various D ES combinations using the COnductor-like Screening MOdel for Realistic Solvents (COSMO-RS), and the most promising systems containing compounds that are Generally Recognized as Safe (GRAS) or accepted by the Cosmetic Ingredient Review (CIR) were subsequently investigated experimentally. Polyethylene glycol 200 and 600 in combination with amino acids, sugars, carboxylic acids and urea were used for D ES formulation. Among them, PEG200-urea showed a significantly higher extraction yield of limonene per g of orange peel (2.7 mg g −1 ) which is approximately 1.4x higher than that obtained with the reference organic solvent, heptane (1.9 mg g −1 ). The limonene extracted with D ES remained stable for at least five weeks when stored at room temperature and in the dark. In addition, hesperidin, a high-value flavonoid for cosmetic applications, was successfully quantified in the extracts, while bergapten (a phototoxic furanocoumarin) and several limonene oxidation products were not detected. Our results show that D ES can achieve limonene yields comparable to, or higher than those of conventional extraction systems while presenting more sustainable metrics. This study emphasizes the potential of D ES for the sustainable limonene extraction from dried orange peels and contributes to circular economy initiatives. • COSMO-RS guided the selection of sustainable D ES for limonene extraction. • PEG200-urea D ES outperformed heptane, yielding 1.4 × more limonene. • D ES-extracted limonene is stable for 5 weeks at room temp and in the dark. • D ES limonene extract also contains hesperidin and suits cosmetic applications. • D ES support greener, circular processes for citrus peel valorization.