Anticandidal Activity of In Situ Methionine γ-Lyase-Based Thiosulfinate Generation System vs. Synthetic Thiosulfinates

Candida albicans and non-albicans Candida species are a common cause of human mucosal infections, as well as bloodstream infections and deep mycoses. The emergence of resistance of Candida spp. to antifungal drugs used in practice requires the search for new antimycotics. The present study unravels the antifungal potential of the synthetic dialk(en)ylthiosulfinates in comparison with an enzymatic in situ methionine γ-lyase-based thiosulfinate generation system (TGS). The kinetics of the TGS reaction, namely, the methionine γ-lyase-catalyzed β-elimination of S-alk(en)yl-L-cysteine sulfoxides, was investigated via 1H NMR spectroscopy for the first time, revealing fast conversion rates and the efficient production of anticandidal dialk(en)ylthiosulfinates. The anticandidal potential of this system vs. synthetic thiosulfinates was investigated through an in vitro assay. TGS proved to be more effective (MIC range 0.36–1.1 μg/mL) than individual substances (MIC range 0.69–3.31 μg/mL). The tested preparations had an additive effect with the commercial antimycotics fluconazole, amphotericin B and 5-flucytosine demonstrating a fractional inhibitory coefficient index in the range of 0.5–2 μg/mL. TGS can be regarded as an attractive candidate for the targeted delivery of antimycotic thiosulfinates and for further implementation onto medically implanted devices.