Oil in Water Microemulsions Loaded with Natural Products Curcumin and Mangiferin Are Effective Against Fusarium verticillioides

The search for harmless alternative solutions to protect crops has become urgent and has recently attracted widespread attention from researchers around the world focusing on natural polyphenols, which represent a treasure chest of molecules with potent activities. Due to the low water solubility of polyphenols, microemulsions were selected as nanovectors. Curcumin and mangiferin solubility in different excipients was evaluated by HPLC. Microemulsion was developed using pseudo-ternary phase diagrams. Sizes and polydispersity of microemulsion globules were evaluated by dynamic light scattering. Activity against Fusarium verticillioides was evaluated by a microdilution method. Vitamin E acetate was selected as the oily phase, Transcutol P as cosurfactant and Tween 80 as surfactant. Smix was composed of Transcutol P and Tween 80 in a 1:2 gravimetric ratio and combined with oil-phase vitamin E acetate at a weight ratio of 3:1. Microemulsions were loaded with 5 mg/mL of each polyphenol and recovery results were 99.5% and 99.3% for curcumin and mangiferin, respectively. Sizes of the lipid phase were 121.7 ± 29.2 nm and 172.6 ± 19.3 nm, respectively, for mangiferin and curcumin microemulsions. F. verticillioides was very susceptible to both microemulsions with a very high activity at a dose of 0.9 mg/mL (log-4 reduction), evidencing a possible use of these nanoformulations to protect crops from F. verticillioides.