Inhibition of yeast-mycelium transformation by 2-alkylthio-6-amino-and 2-alkylthio-6-formamidobenzothiazoles and theirin vitro antifungal activity

Abstract
The antifungal effect of 2-alkylthio-6-amino-and 2-alkylthio-6-formamidobenzothiazoles (22 derivatives in all) onAspergillus niger and variousCandida yeasts was tested. No significant effect was observed withA. niger. With the pathogenic yeast speciesC. albicans andC. guilliermondii, the most efficient derivatives (6-formamido-2-propylthio-, 6-formamido-2-butylthio-, 6-formamido-2-pentylthio-and 6-formamido-2-isopentylthiobenzothiazole) exhibited ED50 values in the range from 2.2 to 21 mg/L and were thus 3–35 times more efficient than 2-mercaptobenzothiazole (Dermacid) that is normally used. 6-Amino-2-pentylthiobenzothiazole was found to be an efficient specific inhibitor of the transformation of the yeast form ofC. albicans to its mycelial one, IC95(M) being 10 mg/L, which was a concentration 25 times lower than MICY+M.