In vitro antibacterial and cytotoxic activity of zinc oxide, iron oxide and silver nanoparticles synthesised from Artemisia afra

The synthesis of nanoparticles using medicinal plants is a potential pathway for developing environmentally friendly drugs with minimal side effects. The aim of this study was to isolate heptadecyl-trans-p-coumarate from the medicinal plant, Artemisia afra, utilise it and its extract to synthesise silver nanoparticles (AgNPs), zinc oxide nanoparticles (ZnONPs) and iron oxide nanoparticles (Fe2O3NPs) that were evaluated for antibacterial and cytotoxic activity. AgNPs synthesised from the coumarate and extract were mostly spherical with an average size of 12 nm and 29 nm, respectively. ZnONPs were mostly rods, plates and spheres with average sizes of 31 nm (extract) and 22 nm (coumarate). Fe2O3NPs were hexagons and spheres with average sizes of 31 nm (extract) and 24 nm (coumarate). Nanoparticles improved the antibacterial activity of the extract and coumarate against Escherichia coli, Pseudomonas aeruginosa, Chromobacterium violaceum and Staphylococcus aureus. Shape of nanoparticles influenced activity; rod-shaped ZnONPs and platelet-like Fe2O3NPs synthesised using the extract exhibited better antibacterial activity. Spherical ZnONPs synthesised using the coumarate and spherical AgNPs showed greater cytotoxicity. The results suggest a synergistic effect between the metal nanoparticles and capping agents. Overall, this study confirms the use of Artemisia afra for the biosynthesis of silver, zinc oxide and iron oxide nanoparticles.