Sustainable valorization of citrus by-products: natural deep eutectic solvents for bioactive extraction and biological applications of Citrus sinensis peel

Every orange peel tossed aside holds a hidden treasure—and green chemistry might just be the key to unlocking it. Could natural deep eutectic solvents turn citrus waste into a powerhouse of bioactive compounds?

Oranges are among the world's most beloved fruits, but their peels often end up as waste. Now, scientists are flipping the script by applying green chemistry principles to turn this byproduct into something valuable. Enter natural deep eutectic solvents (NADES)—a promising, sustainable alternative to traditional organic solvents.

In this study, researchers used choline chloride-based NADES to extract compounds from orange peel. They then analyzed the extracts using chromatography and FTIR spectroscopy, revealing that different NADES varied in their ability to pull out phenolic compounds, which directly influenced antioxidant activity. The volatile profiles were dominated by alcohols, aldehydes, and terpenes, while a control ethanol extract showed higher terpene abundance.

Beyond chemistry, the extracts showed biological promise. All of them boosted pepsin activity without affecting chymotrypsin, but only one—choline chloride:glycerol:citric acid—produced an extract that inhibited trypsin and amylase, as well as the growth of pathogenic microbes. This suggests a targeted potential for digestive enzyme modulation and antimicrobial action.

In short, choline chloride-based NADES could offer a sustainable path to valorize orange waste, extracting valuable bioactives more effectively than old-school solvents. The humble peel may soon become a cornerstone of eco-friendly extraction.

Key Points

• NADES extracts phenolic compounds from orange peel effectively.
• One NADES inhibited trypsin, amylase, and pathogen growth.
• All extracts boosted pepsin but not chymotrypsin activity.