Vol.:(0123456789) 1 3 Chemical Papers https://doi.org/10.1007/s11696-020-01244-9 ORIGINAL PAPER Biogenic synthesis, antioxidant and antimicrobial activity of silver and manganese dioxide nanoparticles using Cussonia zuluensis Strey Nomfundo T. Mahlangeni 1  · Judie Magura 1  · Roshila Moodley 1  · Himansu Baijnath 2  · Hafzah Chenia 2 Received: 24 January 2020 / Accepted: 4 June 2020 © Institute of Chemistry, Slovak Academy of Sciences 2020 Abstract 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 zuluensis Strey, 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 flm surrounding the particles, confrming the capping by biomolecules. AgNPs exhibited better antibacterial activity than MnO 2 NPs and were most active against Escherichia coli and Enterococcus faecalis. MnO 2 NPs presented as ultrathin nanofakes with grainy morphology ranging from 11 to 29 nm when capped with biomolecules from the extract, and presented as nanospheres sur- rounded by nanosheets ranging from 6.99 to 16.57 nm when capped with aralia cerebroside. The radical scavenging activ- ity 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 infuenced by the capping agent, which, in turn, infuenced antioxidant activity as seen with MnO 2 NPs. This study confrms the signifcance of the metal or metal oxide core and capping biomolecules for targeted therapeutic activity of nanoparticles using the plant-mediated synthesis route. Keywords Aralia cerebroside · Silver nanoparticles · Radical scavenging activity · Escherichia coli · Enterococcus faecalis Introduction The synthesis of nanoparticles using biological materials has been proposed to be a non-toxic and eco-friendly alter- native to physical and chemical approaches (Parveen et al. 2016; Nasrollahzadeh et al. 2019). The biological materi- als including DNA, proteins, peptides, bacteria, fungus and plants have been successfully exploited for the synthesis of nanoparticles (Deljou and Goudarzi 2016; Leng et al. 2016; Corra et al. 2017; Julin et al. 2018; Shen et al. 2018; Demir- bas et al. 2019; Guilger-Casagrande et al. 2019). However, plants and plant-derived extracts have gained substantially more interest due to availability, cost-efectiveness and ease of use for large-scale synthesis (Hazarika et al. 2017). More- over, well-characterized and stable nanoparticles have been reported to have been synthesized using plants more than other organisms (Iravani 2011; Ahmed et al. 2016; Demir- bas et al. 2019; Some et al. 2019). Plants are enriched with various bioactive metabolites such as terpenoids, alkaloids, favonoids, sugars, proteins and steroids that act as reduc- ing and stabilizing agents during nanoparticle synthesis (Makarov et al. 2014; Ocsy et al. 2017). Metal nanoparticles have gained popularity over the years, with silver nanoparticles (AgNPs) being widely used due to potential antimicrobial, anti-infammatory and anti- fungal activities (Elgorban et al. 2016; Kedi et al. 2018). The reducing agent used for the synthesis of AGNPs infuences Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11696-020-01244-9) contains supplementary material, which is available to authorized users. * Roshila Moodley moodleyrosh@ukzn.ac.za 1 School of Chemistry and Physics, University of KwaZulu- Natal, Durban 4000, South Africa 2 School of Life Sciences, University of KwaZulu-Natal, Durban 4000, South Africa