Disclosing the Antifungal Mechanisms of the Cyclam Salt H 4 [H 2 ( 4-CF3 PhCH 2 ) 2 Cyclam]Cl 4 against Candida albicans and Candida krusei .

Mycoses are one of the major causes of morbidity/mortality among immunocompromised individuals. Considering the importance of these infections, the World Health Organization (WHO) defined a priority list of fungi for health in 2022 that include Candida albicans as belonging to the critical priority group and Pichia kudriavzevii ( Candida krusei ) to the medium priority group. The existence of few available antifungal drugs, their high toxicity, the acquired fungal resistance, and the appearance of new species with a broader spectrum of resistance, points out the need for searching for new antifungals, preferably with new and multiple mechanisms of action. The cyclam salt H 4 [H 2 ( 4-CF3 PhCH 2 ) 2 Cyclam]Cl 4 was previously tested against several fungi and revealed an interesting activity, with minimal inhibitory concentration (MIC) values of 8 µg/mL for C. krusei and of 128 µg/mL for C. albicans . The main objective of the present work was to deeply understand the mechanisms involved in its antifungal activity. The effects of the cyclam salt on yeast metabolic viability (resazurin reduction assay), yeast mitochondrial function (JC-1 probe), production of reactive oxygen species (DCFH-DA probe) and on intracellular ATP levels (luciferin/luciferase assay) were evaluated. H 4 [H 2 ( 4-CF3 PhCH 2 ) 2 Cyclam]Cl 4 induced a significant decrease in the metabolic activity of both C. albicans and C. krusei , an increase in Reactive Oxygen Species (ROS) production, and an impaired mitochondrial function. The latter was observed by the depolarization of the mitochondrial membrane and decrease in ATP intracellular levels, mechanisms that seems to be involved in the antifungal activity of H 4 [H 2 ( 4-CF3 PhCH 2 ) 2 Cyclam]Cl 4 . The interference of the cyclam salt with human cells revealed a CC 50 value against HEK-293 embryonic kidney cells of 1.1 μg/mL and a HC 10 value against human red blood cells of 0.8 μg/mL.