Combinatorial anti-Trichophyton effects of Ligusticum chuanxiong essential oil components with antibiotics

The antifungal activities of ligustilide and butylidene phthalide, which are major oil components comprising the essential oil of Ligusticum chuanxiong, in combination with antifungal drugs were evaluated. Checkerboard microtiter and microdilution tests were used to measure combined effects against Trichophyton species, T. erinacei, T. mentagrophytes, T. rubrum, T. schoenleinii, T. tonsurans and T. soudanense. Susceptibility of these Trichophyton species to L. chuanxiong essential oil differed distinctly. The fractional inhibitory concentrations (FICIs) against Trichophyton species ranged between 0.27 and 0.56 for ketoconazole combined with ligustilde or butylidene phthalide, indicating synergism or additive effects between the antibiotic and essential oil compounds. Testing by itraconazole instead of ketoconazole, similar combination effects were observed with FICIs from 0.31 to 0.63 against the tested strains of T. mentagrophytes, T. rubrum, T. schoenleinii, and T. soudanense. Thus, data reported here showed that Trichophyton susceptibility to ketoconazole and itraconazole could be notably improved by ligustilde and butylidene phthalide.