Vanillin derivatives as antifungal agents against Aspergillus fumigatus: in vitro activity, in vivo efficacy, and mechanistic insights

The World Health Organization includes Aspergillus fumigatus on the list of fungal pathogens of critical priority for the development of new therapeutic options, due to the emergence of antifungal-resistant strains and high mortality rates. This work evaluated the antifungal activity of vanillin, o-vanillin, ethyl vanillin and vanillin acetate against A. fumigatus. Broth microdilution assays were performed to determine the minimum inhibitory concentrations of the phenolic compounds. Moreover, the ability of vanillin and its derivatives to inhibit conidial adhesion and biofilm formation at subinhibitory concentrations was assessed. The possible mechanism of action of the compounds by molecular docking was determined. Finally, the therapeutic efficacy of the molecules was analyzed in an in vivo aspergillosis model. Vanillin and its derivatives exhibited antifungal effects against A. fumigatus at concentrations of 0.25 to 1 mM; notably, o-vanillin showed higher antifungal activity (0.25 mM). Furthermore, vanillin, o-vanillin and vanillin acetate reduced conidial adhesion, and biofilm formation at subinhibitory concentrations. These compounds decreased ergosterol concentration, and in silico analysis showed that phenolic compounds interact with ERG5, ERG6 and ERG11. Vanillin and o-vanillin demonstrated therapeutic efficacy against aspergillosis model. Overall, these results highlight the antifungal activity of vanillin and o-vanillin against A. fumigatus as a potential therapeutic alternative.