In Vitro Antifungal Activity of Kampo Medicine Water Extracts against Trichophyton rubrum

Kampo medicines consist of a variety of Crude animal, plant, and mineral extracts that have long been used to relieve different symptoms, and are relatively safe. However, their mechanisms of actions have not been well investigated. We screened 61 commercially available Kampo medicines to determine if they contain constituents with antifungal activity against Trichophyton rubrum. The antifungal effect of the Kampo medicines was determined by measuring the mean absorbance of treated fungal culture media. Lower absorbance values suggested a higher inhibition of the growth rate of T. rubrum by the Kampo medicines. We found that seven of the evaluated formulations exhibited a comparable antifungal activity to that of fluconazole at 14 mg/mL. The seven active Kampo medicines were Saiko-keishi-kankyou-to, Saiko-ka-ryukotsu-borei-to, Saiko-keishi-to, Keishi-ka-ryukotsu-borei-to, Dai-saiko-to, Bohu-tsu-sho-san, and Otsu-ji-to. The seven Kampo medicines with antifungal activity contain 30 different crude extracts, and Ou-gon (Scutellaria root) is a supplement contained in six of the seven formulations. Therefore, Ou-gon was considered to play a major role in their antifungal effect. The antifungal assay of the Ou-gon water extract showed that it significantly inhibited the growth of T rubrum at a concentration of 20 mg/mL. Future studies will focus on the isolation and identification of the antifungal components of the crude extracts of Ou-gon, which may be potentially useful, new, and safe antifungal drugs.