Influence of silver nanoparticles synthesized from Chaenomeles leaf extracts on pathogenic microorganisms Klebsiella pneumoniae, Staphylococcus aureus, and Fusarium culmorum

Herein, we report for the first time the biosynthesis of silver nanoparticles (AgNPs) using leaf extracts of Chaenomeles Lindl. (Rosaceae) plants and its spectral characteristics, as well as antifungal and antibacterial activity. Phytosynthesis of silver nanoparticles on the base of aqueous plant extracts and silver nitrate solution was carried out by an ecofriendly and cost-effective approach. UV-Vis spectroscopy was applied to validate the plant-mediated biosynthesis of AgNPs colloidal solutions by the Surface Plasmon Resonance (SPR) bands in the region of 450–500 nm, characteristic of polycrystalline silver nanoparticles. Scanning microscopy (SEM) revealed a wide variation in range 5–58 nm and a close to spherical shape of plant-derived AgNPs. Raman scattering spectroscopy revealed the suitability of biosynthesized silver nanoparticles as the substrates for surface-enhanced Raman scattering (SERS) spectroscopy with the highest efficiency of AgNPs, biosynthesized from leaf extract of Ch. × superba, which enhanced the Rhodamine 6G dye applied at a concentration of 10–7 M. Assay of antifungal activity performed by well diffusion method revealed the dose-dependent effect of all AgNPs against the phytopathogenic fungus Fusarium culmorum. The most effective AgNPs (Ch. speciosa-AgNPs, Ch. cathayensis-AgNPs, and Ch. japonica-AgNPs) achieved a 1.42–1.63 times greater zone of inhibition of the F. culmorum colonies’ growth compared to the corresponding doses of the known chemical fungicide "Quadris". Micro preparations of the zones of incomplete growth inhibition presented changes in the mycelium morphology of F. culmorum due to the action of nanoparticles, such as deformation (curvature, expansion), and a decrease in the hyphae length and density compared to the control sample. Disc-diffusion assay showed notable species-specific antibacterial activity of AgNPs both against Gram-negative (Klebsiella pneumoniae) and Gram-positive (Staphylococcus aureus) strains. Summarizing, the results indicate the undeniable suitability of aqueous leaf extracts of the genus Chaenomeles species for the successful biosynthesis of silver nanoparticles with many useful properties, whose diverse applications require further research.