Fluconazole (Diflucan)

Discovery of novel triazoles containing benzyloxy phenyl isoxazole side chain with potent and broad-spectrum antifungal activity

As a continuation study, 29 novel triazoles containing benzyloxy phenyl isoxazole side chain were designed and synthesized based on our previous work. The majority of the compounds exhibited high potency in vitro antifungal activities against eight pathogenic fungi. The most active compounds 13, 20 and 27 displayed outstanding antifungal activity with MIC values ranging from <0.008 µg/mL to 1 µg/mL, and showed potent activity against six drug-resistant Candida auris isolates. Growth curve assays further confirmed the high potency of these compounds. Moreover, compounds 13, 20 and 27 showed a potent inhibitory activity on biofilm formation of C. albicans SC5314 and C. neoformans H99. Notably, compound 13 showed no inhibition of human CYP1A2 and low inhibitory activity against CYP2D6 and CYP3A4, suggesting a low risk of drug-drug interactions. With high potency in vitro and in vivo and good safety profiles, compound 13 will be further investigated as a promising candidate.

The influence of tea tree oil (Melaleuca alternifolia) on fluconazole activity against fluconazole-resistant Candida albicans strains

The aim of this study was to evaluate the activity of fluconazole against 32 clinical strains of fluconazole-resistant Candida albicans, and C. albicans ATCC 10231 reference strain, after their exposure to sublethal concentrations of tea tree oil (TTO) or its main bioactive component terpinen-4-ol. For all tested fluconazole-resistant C. albicans strains TTO and terpinen-4-ol minimal inhibitory concentrations (MICs) were low, ranging from 0.06% to 0.5%. The 24-hour exposure of fluconazole-resistant C. albicans strains to fluconazole with sublethal dose of TTO enhanced fluconazole activity against these strains. Overall, 62.5% of isolates were classified as susceptible, 25.0% exhibited intermediate susceptibility, and 12.5% were resistant. For all of the tested clinical strains the fluconazole MIC decreased from an average of 244.0 μg/mL to an average of 38.46 μg/mL, and the fluconazole minimal fungicidal concentrations (MFC) decreased from an average of 254.67 μg/mL to an average of 66.62 μg/mL. Terpinen-4-ol was found to be more active than TTO, and strongly enhanced fluconazole activity against fluconazole-resistant C. albicans strains. The results of this study demonstrate that combining natural substances such as TTO and conventional drug such as fluconazole, may help treat difficult yeast infections.