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

The antifungal effect of 2-alkylthio-6-amino- and 2-alkylthio-6-formamidobenzothiazoles (22 derivatives in all) on Aspergillus niger and various Candida yeasts was tested. No significant effect was observed with A. niger. With the pathogenic yeast species C. albicans and C. guilliermondii, the most efficient derivatives (6-formamido-2-propylthio-, 6-formamido-2-butylthio-, 6-formamido-2-butylthio-, 6-formamido-2-penthylthio- 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 of C. albicans to its mycelial one, IC95(M) being 10 mg/L, which was a concentration 25 times lower than MICY+M.