Development of antifungal formulations using silver nanoparticles and natural antimicrobials for food preservation

This study aimed to evaluate natural antifungal agents for controlling food spoilage caused by Botrytis cinerea, Rhizopus stolonifer, and Alternaria brassicae. Various plant-derived essential oils (EOs), including Mediterranean, Pan Tropical, Greek, Canada pine, Nepal pine, clove bud, cumin, Moroccan, and others, as well as 2 citrus extracts, and spherical silver nanoparticles (AgNPs: AGPPH and AGC 0.5) were tested for their antifungal properties. A broth microdilution assay was employed to determine the minimum inhibitory concentrations (MICs) of individual EOs and AgNPs. The potential interactions between EOs and AgNPs were evaluated using the checkerboard method by calculating fractional inhibitory concentration (FIC) indices. The chemical compositions of selected EOs (Mediterranean, Greece, Pan Tropical, and Morocco) were analyzed using high-performance liquid chromatography (HPLC), revealing that over 97 % of their content comprised 15 major components, including trans-cinnamaldehyde, trans-p-methoxy cinnamaldehyde, trans-o-methoxy cinnamaldehyde, cis-cinnamaldehyde, cinnamyl acetate, coumarin, thymol, carvacrol, p-cymene, γ-terpinene, linalool, β-caryophyllene, α-pinene, myrcene and α-terpinene. Based on MIC and FIC results, three active formulations (AFs) were developed: AF1 (Mediterranean EO/Greece EO/Pan Tropical EO/AGC 0.5, 0.3:0.3:2.5:0.05), AF2 (Morocco EO/Greece EO/Pan Tropical EO/AGPPH, 0.3:0.3:2.5:0.05), and AF3 (Morocco EO/Mediterranean EO/Pan Tropical EO/AGC 0.5, 0.3:0.3:2.5:0.05). Their antifungal efficacy was assessed through MIC and agar diffusion assays. The formulations demonstrated strong antifungal activity, inhibiting R. stolonifer (80.7-89.0 %), B. cinerea (96.3-100 %), and A. brassicae (94.3-100 %). These findings suggest that these EO/AgNP-based formulations could serve as effective green antifungal agents for food preservation.