Phyto-mediated synthesis of zinc oxide nanoparticles from Eucalyptus camaldulensis and their antioxidant, antibacterial, and Antiplasmodial activities

The rising incidence of drug-resistant bacteria infections and malaria due to climate change, global health policy and funding gap, among others, underscores the urgent need for novel therapeutic alternatives. In this study, phyto-synthesis of zinc oxide nanoparticles (ZnO NPs) was carried out using aqueous leaf extract of Eucalyptus camaldulensis . The synthesized NPs was characterized using various analytical tools. Antioxidant potential of the NPs was assayed using DPPH, ABTS, and FRAP. Antibacterial assessment of the NPs against five clinical bacterial isolates; Staphylococcus aureus , Escherichia coli , Salmonella typhi , Vibrio cholerae , and Klebsiella pneumoniae was carried out using the agar well diffusion method, while anti-plasmodial activity was evaluated in Plasmodium berghei -infected mice through oral administration of the NPs. The NPs has a hexagonal wurtzite structure, high purity, and an average particle size of 23.94 ± 5.14 nm. The NPs showed a dose-dependent radical scavenging and ferric reducing activities, albeit these were moderately lower than ascorbic acid. A broad-spectrum efficacy against the bacteria isolates was observed with S. aureus and V. cholerae being the most susceptible bacteria isolates. At 200 mg/kg bodyweight, ZnO NPs exhibited 51.9 ± 0.98% chemo-suppression and 70.69 ± 2.68% curative efficacy indicating a significant ( p < 0.05) anti-malarial potential when compared with 90.07 ± 0.34 and 100 ± 0.00% respectively by the positive control; artemether and lumefantrine. These results demonstrate that phyto-synthesized ZnO NPs from E. camaldulensis possess notable antioxidant, antibacterial, and anti-plasmodial properties, supporting their potential as cost-effective, environmentally friendly candidates for managing infectious diseases and malaria.