Upcycling of Citrus Waste by Natural Deep Eutectic Solvents: Green Extraction of Bioactive Compounds with Antioxidant and Regenerative Properties on Human Keratinocytes

Every year, the citrus industry throws away over 40 million tons of waste—but what if that peel could heal your skin? Scientists have found a green way to turn orange and lemon scraps into powerful antioxidants that help human skin cells regenerate.

Citrus waste is a massive environmental headache, but it's also a treasure trove of bioactive compounds. In this study, researchers used natural deep eutectic solvents (NaDES)—a green alternative to traditional chemical solvents—to extract polyphenols from orange and lemon waste. Three NaDES formulations were tested, and all successfully pulled out high amounts of polyphenols, with hesperidin as the star compound.

When human keratinocytes (skin cells) were treated with these extracts, the results were striking. After 24 hours, the extracts significantly reduced intracellular hydrogen peroxide, a marker of oxidative stress. In scratch assays, the extracts accelerated wound closure—the betaine-urea orange extract achieved complete healing within 48 hours. The extracts also boosted IL-6 and IL-8 release, signaling an early pro-regenerative response.

Even more promising, the betaine-urea orange extract protected DNA from damage after genotoxic stress, lowering the number of cells with high 53BP1 foci. This suggests partial DNA protection, a key factor for anti-aging applications.

The takeaway: citrus waste isn't just trash—it's a sustainable source of skin-repairing ingredients. This green extraction method could lead to eco-friendly cosmeceuticals that are both effective and responsible.

Key Points

• NaDES extracts from citrus waste are rich in polyphenols, mainly hesperidin.
• Extracts reduce oxidative stress and speed up wound healing in skin cells.
• Betaine-urea orange extract offers partial DNA damage protection.