Effects of [Cu(2-MeSNic)2(MeNia)2(H2O)2]·H2O and [Cu(2-MeSNic)2(H2O)]2 on Candida albicans

Probable mode of action of new copper complexes of 2-methylthionicotinate (2-MeSNic) of composition [Cu(2-MeSNic)₂(H₂O)₂] and [Cu(2-MeSNic)₂(MeNia)₂(H₂O)₂]·H₂O (where MeNia is N-methylnicotinamide) is described. Both partial growth inhibition of Candida albicans (IC₅₀ ≥ 1.78 mmol·L⁻¹, MIC ≥ 2.5 mmol·L⁻¹) and leak of proteins into the extracellular space (more than 80 %) were observed in the presence of these copper complexes. The membrane damage was detected by staining with Hoechst 33342, propidium iodide and methylene blue. Ascorbic acid potentiated antifungal activity of copper complexes approximately seven-fold and induced the oxidative stress, respectively. The production of intracellular reactive oxygen species was visualized by dichlorofluorescein. Thiobarbituric acid-reactive substances were formed as a by-product of lipid peroxidation.