Temperature-driven antisolvent crystallization of ellagic acid with choline chloride: structure–function mapping and antioxidant performance

Ellagic acid (EA), a bioactive polyphenol, exhibits low aqueous solubility, limiting its pharmaceutical and nutraceutical applications. In this study, EA was recrystallized from ethanol with choline chloride (ChCl) at three controlled temperatures (313.15 K, 333.15 K, and 353.15 K) to enhance its physicochemical properties. The resulting recrystallized ellagic acid (REA) samples were systematically characterized using FTIR, XRD, SEM, DSC, and NMR spectroscopy. XRD analysis revealed improved crystallinity with distinct peak sharpening at 2θ = 28.4° and 29.3° for the 333.15 K REA, while SEM imaging confirmed more defined crystal morphology. Importantly, 1 H NMR spectroscopy revealed chemical shift variations: the aromatic proton signal at 7.47 ppm in native EA exhibited downfield shifts and broadening in the 313.15 K and 353.15 K REA, indicating altered hydrogen bonding and π-π stacking. The 333.15 K REA retained spectral fidelity to native EA, suggesting minimal perturbation in molecular symmetry. These temperature-induced structural modifications significantly enhanced the antioxidant activity, with the 333.15 K REA demonstrating a 1.6-fold increase in DPPH radical scavenging efficiency in comparison with other REA at other temperatures. This study establishes a simple recrystallization approach to modulate EA’s solid-state properties and improve its functional performance. The primary objective is to perform a single-factor evaluation to quantify EA recovery after interaction with ChCl under defined conditions.