Antifungal activity and optimization procedure of silver nanoparticles green synthesized with Prunus laurocerasus L. (cherry laurel) leaf extract

Abstract

In the present study, Box-Behnken design (BBD) was applied to optimize the green synthesis conditions of silver nanoparticles (AgNPs) using Prunus laurocerasus (cherry laurel) leaf extract as a reducing and stabilizing agent. Three important synthesis factors such as the concentration (mM) of silver nitrate (AgNO3), pH of cherry laurel leaf extract and reaction temperature (°C) were used as independent variables of the model, and the absorbance intensity originating from AgNPs was employed as a dependent variable. Statistical analyzes showed that the optimized conditions for the predicted absorbance at 405 nm (2.35 A.U) were determined at a concentration of 10 mM AgNO3, a pH of 9.0, and a temperature of 50°C. The validity of the developed model was verified, and the average absorbance from six experimental runs was recorded as 2.26 (A.U) with an error of 14.86%. In addition, the synthesized AgNPs were characterized using ultraviolet (UV)–visible (Vis) spectroscopy, fourier transform infrared (FT–IR) spectroscopy, and scanning electron microscope (SEM)-energy dispersive X-ray spectroscopy (EDS) was used to examine the morphology and average size of AgNPs. The synthesized AgNPs also showed antifungal activities against all five fungal kiwifruit pathogens tested in vitro. The LC50 values of the synthesized AgNPs were 10.88, 9.30, 7.15, 25.16 and 53.77 µg/ml for Phytopythium vexans, Globisoprangium sylvaticum, G. intermedium, Phytophthora citrophthora and Rhizoctonia solani, respectively. Except for the MIC values of Globisporangium species (120 µg/ml), both MIC and MFC values of the other three species were found to be above 150 µg/ml. The results of this study indicate that AgNPs synthesized using cherry laurel leaf extract should be further investigated for use in the control of fungal root and stem rot diseases in kiwifruit.