Caracterização e atividade antimicrobiana de nanopartículas de óxido de zinco obtidas por síntese verde empregando sulfato de zinco e extrato da bráctea estéril de araucária

Abstract

Green synthesis of zinc oxide nanoparticles (ZnO NPs) using plant extracts represents a sustainable alternative to conventional methods by reducing the use of toxic reagents and promoting the valorization of agro-industrial residues. In this study, ZnO NPs were synthesized using a hydroalcoholic extract of the sterile bracts of Araucaria angustifolia (Bertol.) Kuntze as both a reducing and stabilizing agent. The extracts exhibited high contents of phenolic compounds and flavonoids, which were associated with high antioxidant activity. After synthesis, a reduction in these compounds was observed in the nanoparticles, indicating their involvement in the reduction and stabilization of ZnO. Characterization by Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-Vis) spectroscopy, and fluorescence spectroscopy confirmed the formation of the nanoparticles and demonstrated that calcination altered their optical properties and reduced their fluorescence quantum yield. The green-synthesized nanoparticles exhibited higher antioxidant activity than the control ZnO NPs, particularly before calcination. However, antimicrobial evaluation revealed small inhibition zones against Escherichia coli, Staphylococcus aureus, and Salmonella enterica serovar Typhimurium, indicating the absence of significant antimicrobial activity under the experimental conditions employed. These findings demonstrate that the sterile bracts of A. angustifolia are a promising raw material for the sustainable production of ZnO NPs, contributing to the valorization of plant residues and the development of more environmentally sustainable synthesis routes.