Evaluation effect of physicochemical properties of deep eutectic solvents on phenolic compounds extraction yield from Kultik seed

The aim of this study is to achieve maximum phenolic component extraction efficiency by using deep eutectic solvent, and to gain higher extraction efficiency than that obtained using conventional solvent from fruit waste, namely Kultik seed (Cucumis melo L.). Six DES (deep eutectic solvent) combination were formed using zinc chloride, ethylene glycerol, lactic acid, choline chloride, sorbitol and glucose. The evaluated DES properties were viscosity, pH, %brix and refractometric index, and their effect on phenolic extraction. Overall, the forming components significantly influence DES properties, indicating importance of choosing proper components in DES formation to receive desired extraction result. There was a correlation between extraction yield and DES properties (brix%, pH and viscosity), showing adjusting these properties are crucial in yield of desired phenolic extraction yield, r > 0.5. Alcohol based DESs had lower viscosity, higher brix% and pH in the range of 3–5. Sugar based DESs had higher viscosity, lower brix% and pH other than the range of 3–5. The highest phenolic extraction efficiency was obtained in extraction using alcohol based DESs as solvent, while the extraction using sugar and carboxylic acid based DESs underperformed. Furthermore, the extractions using some DES types (zinc chloride: ethylene glycerol (149.5 mg GAE 100 g−1), choline chloride: ethylene glycerol (161.5 mg GAE 100 g−1)) achieved better phenolic yield than that obtained using conventional solvents (water (7,6 mg GAE 100 g−1), methanol (80.2 mg GAE 100 g−1), ethanol (138.7 mg GAE 100 g−1)). These results indicate that DESs, as a green solvent, provide excellent alternative to organic solvents for green chemistry, and have a great potential to use in industrial applications involving extraction of bioactive compounds from plant sources.