Enhancing solubility of ellagic acid from raspberry biomass using ionic liquids

Abstract

Ellagic acid (EA) is a naturally occurring polyphenolic compound widely present in fruits and berries, recognized for its strong antioxidant, anticarcinogenic, and anti-inflammatory properties. It has been associated with potential protective effects against cancer, cardiovascular diseases, and neurodegenerative disorders. However, its broader therapeutic and commercial applications remain limited due to its poor water solubility and low bioavailability, which also make its extraction from plant materials and incorporation into functional formulations challenging. Traditional extraction methods employing organic solvents such as methanol, ethanol, or acetone are often inefficient, environmentally unsustainable, and inadequate for dissolving hydrophobic compounds like EA. In recent years, ionic liquids (ILs) and natural deep eutectic solvents (NADES) have emerged as promising green alternatives for the extraction of phenolic compounds. Composed of renewable and non- toxic components, these solvents offer tunable solvation capacity, enhanced extraction efficiency, and a low environmental impact, aligning closely with the principles of sustainable chemistry. In this study, whole raspberries and raspberry pomace were investigated as raw materials for ellagic acid extraction. Samples were lyophilized and extracted using 20% aqueous cholinium-based ionic liquids. Six cholinium chloride–based ionic liquids were applied as extraction media, while water and ethanol served as reference solvents for comparison. The obtained extracts were analyzed using HPLC-DAD. All tested ILs significantly enhanced the EA yield compared to water and ethanol, with cholinium acetate proving to be the most efficient, particularly in extractions from raspberry pomace. Furthermore, freeze-dried raspberry pomace yielded higher EA concentrations than whole raspberries, confirming that both solvent composition and biomass pretreatment are key factors of extraction efficiency. Overall, these results demonstrate that cholinium-based ionic liquids are highly effective green solvents for the sustainable extraction of ellagic acid and other phenolic compounds from raspberry-processing residues, thereby supporting the valorization of agro-industrial by-products and the advancement of environmentally responsible extraction technologies.