Biocidal Effect of Plant Extracts Based on Nanoparticles

Abstract

This study fits into the framework of fighting fungal phytopathogens by focusing on the antifungal potential of natural substances and silver nanoparticles (AgNPs). It is divided into two main parts: the synthesis and characterization of AgNPs, and the evaluation of antifungal activity of AgNPs biosynthesized using Aloysia citrodora essential oil, as well as essential oils from A. citrodora (verbena) and Salvia sclarea (sage), against Fusarium oxysporum and Alternaria sp. The synthesis of AgNPs was confirmed by visual observation (color change to yellowishbrown) and UV-Visible spectroscopy. The antifungal tests revealed an overall significant reduction in mycelial growth for both fungi. For F. oxysporum, the A. citrodora essential oil showed the highest inhibition at all doses: 75.55% at 100%, 68.88% at 50%, and 57.77% at 25%. Sage EO showed 71.11% inhibition at 100%, while AgNPs had moderate but stable effects, peaking at 62.96%. For Alternaria sp., A. citrodora EO again exhibited strong efficacy: 84.44% at 100%, 74.81% at 50%, and 64.44% at 25%. Sage EO had 77.03% inhibition at 25%, while AgNPs recorded 78.51% inhibition at 100%. These results confirm the high antifungal potential of A. citrodora EO at all concentrations against both fungi, followed by AgNPs and S. sclarea EO. The observed differences in fungal response suggest potential escape or adaptation mechanisms, especially for F. oxysporum when treated with nanoparticles. The findings support the use of nanoformulated plant extracts as promising, eco-friendly alternatives to chemical fungicides in integrated plant protection strategies.