N-Butylphthalide Potentiates the Effect of Fluconazole Against Drug-Resistant and . Evidence for Its Mechanism of Action.

Objective: To define the antifungal activity of n-butylphthalide alone or in combination with fluconazole in and .

Methods: The antifungal activity of n-butylphthalide alone and in combination with fluconazole was investigated by the classical broth microdilution method and the time-killing curve method. The QRT-PCR method was used to determine gene expressions changes of mitochondrial respiratory chain enzymes, drug efflux pumps and drug target enzymes in and after n-butylphthalide treatment.

Results: The MIC values of n-butylphthalide against and ranged from 16 to 64 μg·mL-1. The FICI value of the combination of n-butylphthalide and fluconazole against drug-resistant and ranged from 0.5001 to 0.5315 with partial synergism. Time-killing curves showed that 256 μg·mL-1 n-butylphthalide significantly inhibited the growth of drug-resistant colonies of and , and 128 μg·mL-1 n-butylphthalide combined with 1 μg·mL-1 fluconazole had an additive effect. N-butylphthalide could alter the expression of mitochondrial respiratory chain enzymes , and genes in and (< 0.05) and downregulate the expression of the drug efflux pump genes and in drug-resistant to 3.36% and 3.65%, respectively (<0.001), but did not affect the drug target enzyme ERG11 in drug-resistant .

Conclusion: N-butylphthalide had antifungal activity against and . N-butylphthalide improved the activity of fluconazole against drug-resistant by affecting the expression of mitochondrial respiratory chain enzyme genes and reversing the high expression of drug efflux pump genes CDR1 and CDR2.