Antifungal and antimycotoxin activity of plant-synthesized silver nanoparticles (AgNPs): A novel approach to combat food contamination

Fungi and mycotoxins hugely contaminate food and feed commodities and consequently contribute to adverse effects on health and the economy. While various measures have been adopted to control food contamination, the potential application of nanotechnology to control fungi and mycotoxins in food seems promising; nevertheless, it has not been sufficiently explored. This study investigated the antifungal effect of plant-mediated silver nanoparticles (AgNPs) form Garcinia kola, Carica papaya, Achillea millefolium, Ocimum gratissimum, and Perilla frutescens against ten food-borne fungi. Furthermore, the effect of Garcinia kola AgNPs and Achillea millefolium AgNPs against aflatoxin (AFB1 and AFB2) and ochratoxin (OTA and OTB) production by Aspergillus flavus, Aspergillus ochraceus, and Aspergillus clavatus was determined by using an Ultra Performance Liquid Chromatography-Triple Quadrupole Spectrometry (UPLC-MS/MS) instrument to quantify the amount of aflatoxins and ochratoxins produced following AgNPs antifungal treatments. The characterization analysis of AgNPs showed that stable and crystalline AgNPs were bioformulated, with sizes ranging from 10.9 to 67.5 nm. The antifungal effect of AgNPs by agar well diffusion method after 7 days of incubation revealed that at a concentration of 100 mg/L, AgNPs were able to exhibit an antifungal effect on the tested food-borne pathogens. As found, a maximum inhibitory zone (MIZ) of 20.3 mm by Penicillium frutescens AgNPs on Penicillium chrysogenum was obtained, while a 10.7 mm MIZ exhibited by Carica papaya AgNPs on Aspergillus Niger was recorded. Mycelial growth inhibition (MGI) activity of AgNPs at varying concentrations of 6.25, 12.5, 25, 50, and 100 mg/L was established. The highest MGI of AgNPs of 100 % was recorded against Penicillium citrinum, while the lowest MGI of 6.7 % for Aspergillus flavus was noted. The significant difference at p ≤ 0.05 was validated by comparing MIZ and MGI induced by the tested AgNPs to the control groups. The ability of AgNPs derived from Garcinia kola and Achillea millefolium showed a reduction in mycotoxin (AFB₁, AFB₂, OTA, and OTB) production as the concentration of the synthesized AgNPs increased. These findings demonstrate that AgNPs have immense potential as antifungal agents for controlling the growth of fungi and the subsequent biosynthesis of their respective mycotoxins.