Exploring a Sustainable Process for Polyphenol Extraction from Olive Leaves

Area of Science:

• Agricultural Science
• Food Chemistry
• Green Chemistry

Background:

• Olive leaves, agricultural residues, pose environmental challenges.
• These leaves are rich in polyphenols with potential health benefits for chronic diseases.
• Polyphenol extraction faces technological hurdles due to compound instability.

Purpose of the Study:

• To evaluate pressurized liquid extraction (PLE) for extracting polyphenols from olive leaves.
• To assess the impact of green solvents (water-ethanol, water-glycerol) and temperature on extract composition.
• To obtain polyphenol-rich antioxidant extracts with reduced sugar content.

Main Methods:

• Pressurized liquid extraction (PLE) was employed.
• Water-ethanol and water-glycerol mixtures (0-15%) were used as green solvents.
• Extractions were performed at 50°C and 70°C.

Main Results:

• The optimal condition was 30% ethanol at 70°C, yielding the highest polyphenol content (15.29 mg GAE/g DW) and antioxidant activity (IC50: 5.49 mg/mL, ORAC: 1259 μmol TE/g DW).
• This condition also resulted in lower glucose (3.75 mg/g DW) and fructose (5.68 mg/g DW) content compared to glycerol mixtures.
• Ethanol favored flavanol, stilbene, and secoiridoid recovery, while glycerol enhanced phenolic acid and flavonol extraction.

Conclusions:

• Pressurized liquid extraction with green solvents is effective for valorizing olive leaf waste.
• Solvent composition significantly influences the type and quantity of polyphenols extracted.
• Optimizing solvent mixtures and temperature is crucial for efficient polyphenol recovery and reduced sugar co-extraction.