In silico/in vitro antifungal evaluation of bis(5-cycloalkylsulfenyl-1,3,4-thiadiazole-2-sulfenyl) alkane derivatives against Candida albicans and Aspergillus Niger

The in silico and in vitro antifungal activities of a series of bis(cycloalkylsulfenyl)-1,3,4-thiadiazole derivatives were evaluated against Candida albicans (C. albicans) and Aspergillus niger (A. niger). Crystallographic analysis of 1,6-bis(2-cyclopentylsulfenyl-1,3,4-thiadiazole-5-sulfenyl)hexane (C5C6TD) in the monoclinic P21/n space group revealed coplanar 1,3,4-thiadiazole-2-sulfenyl rings and a hexamethylene spacer, with twist-envelope cyclopentyl conformations. In vitro MTT assays confirmed all derivatives were non-toxic to RAW 264.7 macrophages at the tested concentration range of 3.125-100 μg mL−1. In silico ADMET and ProTox-III predictions showed that carbon spacer length influenced pharmacokinetics and toxicity; six-carbon spacers were predicted to be class VI toxic, whereas four-carbon spacers were class IV. All derivatives demonstrated prominent in vitro antifungal efficacy, with minimum inhibitory concentrations (MICs) between 8 and 64 μg mL−1. Compound C5C6TD specifically exhibited MICs of 62.5 and 31.25 μg mL−1 against C. albicans and A. niger, respectively. Furthermore, computational docking analysis indicated robust binding pocket interactions with target proteins, showing excellent binding energies of −10.67 kcal mol−1 for lanosterol 14-alpha demethylase (PDB: 5V5Z) and −10.32 kcal mol−1 for glucose oxidase (PDB: 1GAL). These findings highlight the therapeutic potential of these thiadiazoles as safe, active antifungal agents.