Comparison of green solvents for the revalorization of orange by-products: Carotenoid extraction and in vitro antioxidant activity

Orange peels are packed with hidden treasure—carotenoids—and a new green solvent just proved it can unlock more of it than traditional hexane. Could food waste become a goldmine of natural colorants?

Every year, millions of oranges are squeezed for juice, leaving behind peels that often go to waste. But those peels are rich in carotenoids—natural pigments with antioxidant power. The challenge has always been extracting them efficiently without harsh chemicals. This study set out to compare greener alternatives: vegetable oils, fatty acids, and deep eutectic solvents (DES).

Among them, a new hydrophobic DES made from octanoic acid and L-proline—nicknamed C8:Pro—stood out. It extracted 46.01 µg of carotenoids per gram of peel, beating hexane's 39.28 µg. Its antioxidant activity also led the pack at 2438.8 µM TE/mL, measured across three different assays.

The team didn't stop at performance. They characterized the solvent's chemistry and scored its environmental footprint using two sustainability assessment models. The verdict? C8:Pro is not only effective but genuinely green.

This isn't just about better extraction. It's a step toward a circular economy, where orange peel waste becomes a valuable ingredient for natural colorants and health-promoting additives. The peel you toss could one day color your food—and protect your cells.

Key Points

• New DES C8:Pro outperforms hexane in carotenoid extraction
• Highest antioxidant activity recorded in C8:Pro extracts
• Green solvents validated by two sustainability assessment models