Nanostructured delivery systems for antioxidants: Comparative release of purified ellagic acid and extracted polyphenols

Despite their proven antioxidant and anticancer effectiveness, polyphenolic compounds have limited bioavailability, which drives the need to employ polymeric materials for their encapsulation to achieve precise and sustained release. In this study, ellagic acid (EA) and a phenolic-rich pecan nut extract (PRE) were encapsulated within poly(ε-caprolactone) (PCL) microparticles in a double emulsion system using poly(vinyl alcohol) as stabilizer. After solvent evaporation, the resulting particles were characterized by DLS, SEM, and FTIR, and in vitro release in PBS (pH 7.4) was quantified as the fraction released (F). Release data were fitted to zero-order, first-order, Higuchi, Korsmeyer–Peppas, and Hixson–Crowell models. For EA at 2.5 and 5.0 mg/mL, $\ln (1-F)$ versus time exhibited the highest correlation ($R^2\approx 0.93$), indicating first-order release, whereas at 10 mg/mL, the cube-root transformation (${(1-F)}^{1/3}\mathrm{vs}.t$) achieved superior fit, consistent with surface-erosion kinetics. Although both EA and PRE follow similar overall mechanistic regimes, PRE exhibits significantly slower, concentration‑dependent release, particularly at higher loadings, indicating that its complex phenolic matrix modulates diffusion and erosion pathways differently than pure EA. These findings underscore the tunability of PCL/PVA matrices for hydrophilic phenolics and highlight the importance of bioactive compound concentration in dictating diffusion versus erosion-controlled release, offering a nanomedicine platform for sustained delivery of bioactive compounds.