Sustainable production of phloretin using multi-dimensionally adjustable acidic deep eutectic solvents as multifunctional solvents for green and efficient valorization of Malus plant pruning waste

To effectively harness and valorize the often-overlooked pruning waste from Malus plants, an eco-friendly and efficient strategy for the simultaneous extraction and in situ de-glycosylation to prepare phloretin was introduced for the first time. By designing an acidic deep eutectic solvent (DES) system and adjusting the polarity and hydrophilicity of the non-acidic component as well as the acidity of the acidic component, a significant enhancement in the extraction yield and de-glycosylation efficiency of phloretin and its glycoside derivatives was achieved. The highest phloretin content was attained using ethylene glycol (EG) - p-toluenesulfonic acid (PTSA) (2:1), which consisted of ethylene glycol and p -toluenesulfonic acid with a molar ratio of 2:1 and 30 % water content. After treatment condition optimization, a peak phloretin content of 139.9380 ± 0.2191 μmol/g was achieved, which notably surpassed traditional organic solvent extraction methods. Furthermore, the phloretin was successfully recovered from the EG-PTSA (2:1) solution using macroporous resin adsorption method, with SP825 resin showing a recovery rate of 85.87 %. Applicability analysis confirmed that the EG-PTSA (2:1) treatment method is suitable for various Malus plant pruning wastes. As a result, this study not only offered a justification for improving the extraction and de-glycosylation efficiency through multi-dimensional modification of the acidic DES but also presented an innovative approach for utilizing Malus plant pruning waste.