Green synthesis of silver nanoparticles using <i>Plathymenia reticulata</i> bark extract and toxicological assessment in <i>Allium cepa</i>

The aim of this study was to examine the antioxidant potential of the aqueous bark extract of <i>Plathymenia reticulata</i>, a native Brazilian specie rich in phenolic compounds, and its effectiveness as a reducing and stabilizing agent in the green synthesis of silver nanoparticles (AgNPs). This approach offers a promising strategy in green nanotechnology by harnessing the unique phytochemical profile of a native plant specie to produce biologically active nanoparticles with potential applications in environmental and biomedical fields. The resulting AgNPs exhibited physicochemical properties suitable for biological applications, including an average size of 43.6 nm, stable colloidal dispersion, and antioxidant functional groups adsorbed on their surface. To assess their biological impact, <i>Allium cepa</i> was selected as a sensitive bioindicator due to its well-established use in cytotoxicity and phytotoxicity assays. During the vegetative phase of <i>Allium cepa</i>, these nanoparticles influenced root growth and mitotic index (MI). Higher concentrations of green synthesized AgNPs significantly stimulated root elongation, while MI was reduced, especially at the highest dose tested, suggesting a possible interference with cell division processes. Data indicate that, at the tested concentrations, green synthesized AgNPs did not initiate any marked phytotoxic effects even after prolonged exposure. These findings highlight the innovative use of <i>P. reticulata</i> in green nanotechnology and reinforce the importance of evaluating genotoxic risks prior to environmental or biotechnological applications.