Green synthesis of ZnO NPs via salvia hispanica: evaluation of potential antioxidant, antibacterial, mammalian cell viability, H1N1 influenza virus inhibition and photocatalytic activities

Among different forms of metallic nanoparticles (NPs), zinc oxide (ZnO) NPs with a very special bandgap of 3.37 eV and considerable binding energy of excitation (60 meV at room temperature), have been classified as high-tech nanoparticles. This study aimed to synthesize ZnO NPs using the extract from Salvia hispanica leaves. The synthesized nanoparticles were fully characterized and the photocatalytic activity was evaluated through the degradation of methylene blue. Additionally, the potential in vitro biological activities of such ZnO NPs in terms of their antibacterial activity were determined, as well as their antioxidant (30 minutes), antiviral (48 hours) and mammalian cell viability properties (48 and 72 hours). This study is the first investigation into the synthesis of such green ZnO NPs mediated by this plant extract, in which both photocatalytic and biomedical properties were found to be promising. The IC50 values for the antibacterial activities were found to be around 17.4 μg mL^–1 and 28.5 μg mL^–1 for S. aureus and E. coli, respectively, and the antioxidant activity was comparable with the standard BHT. However, the H1N1 inhibition rate using the present green ZnO NPs was lower than oseltamivir (up to about 40% for ZnO NPs and above 90% for oseltamivir) which was expected since it is a drug, but was higher than many synthetic nanoparticles reported in the literature. In addition, the mammalian cell viability assay showed a higher than 80% cellular viability in the presence of 5, 10 and 20 μg mL^–1 nanoparticles, and showed a higher than 50% cellular viability in the presence of 50 and 75 μg mL^–1 nanoparticles. In this manner, this study showed that these green ZnO NPs should be studied for a wide range of medical applications.