Towards a sustainable recovery of polyphenols from agrifood waste: Performance of polymeric sorbents with natural deep eutectic solvent extracts

Olive oil production leaves behind mountains of waste—yet hidden inside those discarded leaves are powerful antioxidants worth recovering. Now, scientists are testing green solvents and special polymers to unlock them.

Every drop of olive oil comes with a shadow: massive amounts of waste. But those discarded olive leaves are not trash—they are treasure troves of phenolic compounds, natural antioxidants with real commercial value. The challenge? Extracting them sustainably and purifying the result without harsh chemicals.

Enter natural deep eutectic solvents (NaDESs), a new class of green solvents that have proven remarkably effective at pulling phenolics out of agrifood waste. But extraction is only half the battle. The resulting extracts must be cleaned up before they can be used in food, drugs, or cosmetics. That's where polymeric sorbents come in—porous materials that selectively capture and release target molecules.

In this study, researchers tested four non-functionalized polymeric sorbents—PuroSorb PAD900, PAD950, PAD610, and Macronet MN202—to purify NaDES extracts from olive leaves. Working at the extract's natural pH of 5.3, they found all four sorbents performed well, with MN202 showing a special talent for retaining 3-hydroxytyrosol, a potent antioxidant. For desorption, ethanol-water mixtures did the job: over 70% ethanol released most phenolics, while below 50% worked best for small polar molecules like 3-hydroxytyrosol.

What makes this work stand out? Such sorbent characterization is routine for conventional solvents, but for NaDES extracts, it remains rare and novel. This study helps close that gap, moving us closer to a circular economy where waste becomes a resource.

Key Points

• Four polymeric sorbents tested on NaDES olive leaf extracts
• MN202 best retained 3-hydroxytyrosol at pH 5.3
• Ethanol >70% desorbs most phenolics; <50% for small polar