Valorization of red propolis residue in poly(ε-caprolactone) films for bioactive material development

The industrial production of red propolis hydroalcoholic extract generates 40–50 wt% of residual biomass, which remains largely unexploited. In this study, we valorize unused red propolis residue (RPR) as a bioactive component in poly(ε-caprolactone) (PCL)-based composite films produced via hot pressing, thereby converting a potential waste into a functional material. Films containing 10, 25, and 50 wt% RPR were fabricated and systematically characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal analyses (DSC/DTG). FTIR confirmed the successful incorporation of propolis-derived functional groups into the polymer matrix, while shifts in DTG peaks at higher loadings indicated partial interfacial compatibility between RPR and PCL. Despite the residue retaining low levels of flavonoids, in vitro release assays (n = 3) revealed a diffusion-controlled release of bioactive compounds, reaching up to 60 µg over ten weeks. These findings support a sustainable strategy for red propolis by-product valorization and introduce a PCL-based composite film with potential for prolonged bioactive compound delivery and future applications as a bioactive biomaterial.Graphical abstractSustainable reuse of red propolis residue for bioactive polymer composite production.