Biosynthesis of Silver Nanoparticles Using Ocimum basilicum Extract and Evaluation of Their Antifungal Efficacy Against Selected Fusarium Plant Pathogens

Fusarium species are significant phytopathogens responsible for major crop losses and contamination of food products with harmful mycotoxins, posing serious risks to food security and public health. In response to the limitations of conventional agrochemicals, this study explores sustainable antifungal strategies based on plant-derived products and nanotechnology. The aqueous extract of Ocimum basilicum was investigated as a bioresource for both direct antifungal activity and the green synthesis of silver nanoparticles (OB-AgNPs). Liquid chromatography–mass spectrometry (LC-MS) analysis of the O. basilicum aqueous extract revealed the presence of key compounds, including rosmarinic and chicoric acids, which can reduce and stabilize AgNPs. The biosynthesized nanoparticles were characterized using standard analytical techniques, including UV–visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), high-resolution transmission electron microscopy (HRTEM), and powder X-ray diffraction (PXRD). The OB-AgNPs exhibited a surface plasmon resonance (SPR) peak at 437 nm, a zeta potential of ~–16.3 mV, an average size of 28 nm (TEM) while the average hydrodynamic size is ≈57 nm (DLS). The synthesized AgNPs demonstrated stability in potato dextrose broth (PDB) for up to 24 h. The nanoparticles alongside the aqueous extract were evaluated against selected mycotoxigenic Fusarium species including F. verticillioides, F. proliferatum, F. subglutinans, F. graminearum, and F. globosum, following 96 h of exposure. Results showed that the aqueous O. basilicum extract exhibited limited antifungal activity, with significant inhibition observed only against F. globosum MRC 6122 at the highest concentration tested (400 ng/µL). In contrast, the biosynthesized OB-AgNPs demonstrated potent antifungal activity against most of the tested Fusarium strains, except for F. proliferatum MRC 8549 and MRC 8550, indicating substantially greater efficacy than the crude extract. These findings highlight the potential of O. basilicum-mediated AgNPs as effective and eco-friendly antifungal agents. The study underscores the value of integrating plant-based phytochemicals with nanotechnology for controlling Fusarium pathogens, while emphasizing the need for future studies to determine their effects on mycotoxin production, as well as their safety and phytotoxicity for agricultural applications.