Optimization of green-synthesized silver nanoparticles by using Madımak (Polygonum cognatum Meissn.) extract and its antifungal activity against some Phytophthora species

The present study used Madımak (Polygonum cognatum Meissn.) plant extract as a reducing agent to create silver nanoparticles (AgNPs). The Box-Behnken Design of Response Surface Methodology was used to investigate the combined effect of four different synthesis variables in order to obtain the maximum amount of AgNPs produced. Optimal AgNP production was achieved within the investigated range when the AgNO3 concentration, plant extract/AgNO3 ratio, solution pH, and microwave power were 10 mM, 0.15, 9 and 800 watt, respectively. The UV–Vis, FT–IR, and SEM-EDX analysis were utilized to characterize the synthesized AgNPs. Additionally, it was revealed that the EC50 values of AgNPs synthesized for the remaining 6 Phytophthora species (P. cactorum, P. capsici, P. citrophthora, P. cinnamomi, P. nicotianae and P. palmivora), except P. citrophtora, whose EC50 value could not be determined in in vitro experiments, varied between 217.10 and 511.83 µg ml-1. On the other hand, MIC values for all fungi were above 400 µg ml-1. The results indicate that Madımak-AgNPs should be further investigated for use in the control of Phytophthora diseases.