Insights into the mode of action of 2-(4-methoxyphenyl)ethyl isothiocyanate on Aspergillus niger

Isothiocyanates had attracted attention for many years due to their antimicrobial properties. In this study, the antifungal efficiency of eighteen isothiocyanate compounds were evaluated against six plant pathogenic fungi and two molds in vitro. Among them, 2-(4-methoxyphenyl)ethyl isothiocyanate displayed the highest antifungal activity against Aspergillus niger (EC50 = 4.19 μg/mL). The further studies of its mode of action showed that it may damage the cell morphology and membrane integrity in a dose dependent manner by morphological observation, propyl iodide staining and the release of cellular contents. On the other hand, the decrease of related enzyme activities in tricarboxylic acid cycle suggested that 2-(4-methoxyphenyl)ethyl isothiocyanate may effected energy metabolism. Besides, reactive oxygen species, the content of malondialdehyde, the total antioxidant capacity, the content of glutathione and the kinase of oxidative reactive were changed in fungi treated with 2-(4-methoxyphenyl)ethyl isothiocyanate, compared with those in untreated fungi, which all indicated that 2-(4-methoxyphenyl)ethyl isothiocyanate exhibited antifungal activity against A.niger by inducing oxidative stress.