Biogenic synthesis, antioxidant and antimicrobial activity of silver and manganese dioxide nanoparticles usingCussonia zuluensisStrey

Synthesis of nanoparticles using naturally occurring biomolecules has become the preferred method due to increased concerns over environmental degradation. In this study, the biosynthesis of manganese dioxide nanoparticles (MnO(2)NPs) and silver nanoparticles (AgNPs) using extracts and the biomolecule, aralia cerebroside, isolated from the medicinal plant species,Cussonia zuluensisStrey, was investigated. The size and morphology of nanoparticles observed using microscopic techniques indicated an average particle size of 7.43 nm (spherical and polydispersed) for AgNPs and a layer of thin film surrounding the particles, confirming the capping by biomolecules. AgNPs exhibited better antibacterial activity than MnO(2)NPs and were most active againstEscherichia coliandEnterococcus faecalis. MnO(2)NPs presented as ultrathin nanoflakes with grainy morphology ranging from 11 to 29 nm when capped with biomolecules from the extract, and presented as nanospheres surrounded by nanosheets ranging from 6.99 to 16.57 nm when capped with aralia cerebroside. The radical scavenging activity was found to be MnO(2)NPs (extract) > MnO(2)NPs (cerebroside) > AgNPs (extract) > extract > cerebroside, and the ferric reducing antioxidant power was found to be cerebroside > extract > MnO(2)NPs (cerebroside) > MnO(2)NPs (extract) > AgNPs (extract). MnO(2)NPs exhibited better antioxidant activity than AgNPs with size and morphology of nanoparticles being influenced by the capping agent, which, in turn, influenced antioxidant activity as seen with MnO(2)NPs. This study confirms the significance of the metal or metal oxide core and capping biomolecules for targeted therapeutic activity of nanoparticles using the plant-mediated synthesis route.