Synthesis and optimization of a 2-isopropenyl-2-oxazoline based polymer for enhanced phenolic acid extraction

Phenolic acids, widely present in plants, plant-based foods, and human metabolites, are well known for their potent antioxidant properties, which are mainly attributed to their phenolic hydroxyl groups. The number and position of these hydroxyl groups, together with methoxy and carboxylic acid groups significantly influence their antioxidant capacity. In this study, five different phenolic acids were studied: chlorogenic acid, caffeic acid, 2,3-dihydroxybenzoic acid, ferulic acid and trans-cinnamic acid. They were analyzed by solid phase extraction and high-performance liquid chromatography hyphenated to ultraviolet detection. Different polymers for solid phase extraction were synthesized using ultraviolet photoinitiation with ethylene glycol dimethacrylate and thermal initiation with divinylbenzene as crosslinkers. The monomer utilized in this process was 2-isopropenyl-2-oxazoline, which exhibited analogous properties to the commonly known monomers employed in the polymerization process for commercially available solid phase extraction cartridges. The most effective polymer was optimized and applied to two different types of honey, demonstrating its ability to extract phenolic acids from matrix compounds.