Antifungal activity of eugenol on Cryptococcus neoformans biological activity and Cxt1p gene expression

The present study was targeted toward investigating the effects of eugenol on Cryptococcus neoformans biological activity and Cxt1p gene expression.

For the purpose of the study, the growth, urease, synergism activity, and disk diffusion of C. neoformans were assessed in eugenol-treated culture. The minimum inhibitory concentration (MIC) was determined by the Clinical and Laboratory Standards Institute M27-A3 method at a concentration range of 0.062-2 mg/mL. Subsequently, the expression of Cxt1p genes was studied at the MIC₅₀ concentration of eugenol using real-time polymerase chain reaction.

The obtained results showed that eugenol at the concentrations of 125 and 500 µg/mL resulted in 50% and 100% growth inhibition in C. neoformans, respectively. In terms of urease activity, the results showed that the addition of MIC₅₀ of eugenol and fluconazole to urea medium reduced urease activity in C. neoformans. In the culture treated with eugenol, the inhibition zone of antifungal drugs, namely amphotericin B, itraconazole, and fluconazole, was increased to 36±0.002, 22±0.001, and 12±0.002 mm, respectively. The expression levels of Cxt1p in the eugenol-treated, fluconazole-treated, and non-treated samples were estimated at 46%, 58%, and 100%, respectively.

The findings of the current study revealed that eugenol could cause C. neoformans growth inhibition and reduce Cxt1p expression in this species. As the results indicated, the susceptibility of C. neoformans to fluconazole was increased when combined with eugenol.