Antifungal activity of polyphenolic compounds against fluconazole-susceptible and -resistant Candida species.

Background and objectives: The rapid emergence of resistant fungi is occurring worldwide, and this crisis has been attributed to the lack of new antifungal drug development. This issue emphasizes the need for innovation in finding novel antifungals. There is an increasing interest in using the natural products of plants with high biological activity as alternatives to synthetic drugs. This study aimed to evaluate the possible applicability of polyphenols as alternative antifungal drugs to treat resistant Candida infections.

Materials and methods: A panel of fluconazole-resistant (n=14) and fluconazole-susceptible (n=26) clinical Candida isolates was obtained from the reference culture collection. The determination of the minimum inhibitory concentrations (MICs) of fluconazole, tannic acid, rosmarinic acid, gallic acid, chlorogenic acid, caffeic, ferulic, and p-coumaric was carried out following the Clinical and Laboratory Standards Institute (CLSI) guidelines.

Results: The MIC values of 40 Candida species isolates ranged from 0.25 to >64 μg/mL for polyphenolic compounds. The highest inhibitory effect against Candida species was observed with tannic acid, followed by fluconazole. Non-albicans Candida groups were more sensitive to tannic acid compared to C. albicans isolates. Significant differences were observed in the MICs of fluconazole and tannic acid against non-albicans Candida isolates.

Conclusion: The increasing antifungal resistance highlights the importance of evaluating new drugs that are more robust against resistance. This study suggests that tannic acid could be considered a novel antifungal agent for managing fungal infections, including multidrug-resistant non-albicans Candida infections.