Impacts of the Herbal Antimicrobial Compounds on the Antimicrobial Potency of Green Synthesized Copper Nanoparticles.

Plant-mediated synthesis is a most recent approach toward green synthesis of copper-based nanoparticles. In this approach nanoparticles are capped with phytochemicals, suggesting that plants with unique biological properties might transfer these benefits to the nanoparticles. However, there is no experimental evidences to directly corelate bioactivities of nanoparticles to their capping phytochemicals. This study aims to assess the impacts of herbal antimicrobial compounds on the antimicrobial potency of resulted nanoparticles. Cu(OH)2 nanoparticles (CuNPs) were synthesized by leaf extracts of eucalyptus and tobacco. Resulted particles were characterized to exhibit similar physicochemical properties which are determinative for antimicrobial activity. Antimicrobial effects of the leaf extracts and CuNPs were tested against Staphylococcus aureus and Escherichia coli. Eucalyptus leaf extract was found effective against S. aureus with growth inhibition zone of 13.1 ± 0.6 mm. CuNPs exhibited efficacy against both bacterial strains with inhibition zones exceeding 15 mm. Notably, no significant difference in antimicrobial effectiveness of CuNPs was observed, suggesting that the antimicrobial superiority of eucalyptus extract was not transferred to nanoparticles. These results could reshape our understanding about the impacts of herbal bioactive molecules on the bioactivity of plant-mediated synthesized nanoparticles.