Effects of antioxidants on in vitro growth of Thecaphora frezzii

Thecaphora frezzii, the causal agent of peanut smut, causes significant grain losses in Argentina. Current control strategies are insufficient to manage this pathogen. We investigate the effect of antioxidants on the in vitro development of T. frezzii hyphae, to identify compounds with antifungal activity, also evaluate protein and lipid profiles as potential targets for these compounds.

The antifungal activity was evaluated in both, solid and liquid media, and minimum inhibitory concentration and minimum fungicidal concentration were calculated. The protein profile was assessed using sodium dodecyl sulfate polyacrylamide gel electrophoresis, while lipids were analyzed by thin-layer chromatography (TLC) and gas chromatography with flame ionization detection, both before and after hyphal treatment. Lipase activity was analyzed using agar Tween 20 and TLC, while lipid peroxidation was evaluated by the thiobarbituric acid-reactive substance (TBARS)assay. Microscopy was used to observe morphological and metabolic changes. Butylated hydroxyanisole, methylparaben, and lipoic acid showed inhibitory effects on T. frezzii. Lipoic acid was chosen for further study due to its lack of environmental toxicity. Lipoic acid induced the loss of cytosolic proteins, hydrolysis of triglycerides, and increased levels of free fatty acids, monoacylglycerols, and diacylglycerols. It also caused a decrease in ergosterol levels and alterations in the fungal cell wall and membrane, ultimately leading to cell death.

This study demonstrates the efficacy of lipoic acid in inhibiting the in vitro development of T. frezzii.