Antifungal activity of isothiocyanates extracted from horseradish (Armoracia rusticana) root against pathogenic dermal fungi

To develop natural antifungal agents against pathogenic dermal fungi, the antifungal activity of isothiocyanates (ITCs) extracted from horseradish (Armoracia rusticana) root was investigated. A paper disk diffusion assay showed that ITCs inhibited growth of the four pathogenic dermal fungi (Trichophyton rubrum, Trichophyton mentagrophytes, Microsporum canis, and Epidermophyton floccosum) at 5000 μg/mL, as well as perfectly inhibited the growth of the fungi at 10,000 μg/mL in a concentration-dependent manner. The minimum inhibitory concentrations of ITCs against T. rubrum, T. mentagrophytes, M. canis, and E. floccosum were 200, 200, 100, and 100 μg/mL, respectively. The minimum fungicidal concentrations of ITCs against the four pathogenic dermal fungi were 200 μg/mL. These results strongly suggested that ITCs extracted from horseradish root can be a candidate of natural antifungal agents against pathogenic dermal fungi, even though further study is needed to investigate how to use ITCs in clinical therapy.