Antimycotic activity of Nigella sativa oil-gold nanocomposites against fungal isolates from stored maize

Abstract

Fungi contamination in grains is a serious health menace that reduces the quality and nutritional content of stored food grains. Hence, in this study, the antimycotic activity of Nigella sativa (NS) oil-gold nanocomposite against fungi isolated from stored maize was evaluated. The fungal species were isolated from stored maize and identified using standard procedure. Gold nanoparticles (AuNPs) were biosynthesized from an aqueous extract of Piper guineense leaf and characterized by the Tyndall effect, UV-visible spectra, zeta sizer, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). Gas chromatography-mass spectrometry (GC-MS) analysis of NS oil identified 8 chemical compounds, with Cyclododecyne being the most abundant (39.49 %). The obtained AuNPs were conjugated with NS oil to form nanocomposites. Piper guineense contains important phytochemicals that are capable of reducing chloroauric acid (HAuCl4) into AuNPs. The dispersion of light through the colloidal AuNPs solution was confirmed by the Tyndall effect. The AuNPs were spherical in shape and well-dispersed with average sizes ranging from 30 to 120 nm. The UV-visible spectrum showed a peak of 530nm while the FTIR result revealed the presence of different chemical groups in AuNPs. The formulated Nigella sativa oil nanocomposite III exhibited the highest anti-fungal activity, minimum inhibitory concentrations (MIC), and minimum fungicidal concentrations (MFC) against fungal isolates from both fields and stored maize. This outcome indicated that Nigella sativa oil nanocomposites could serve as an effective protectant against fungi infection in maize.