Introduction: It was shown previously that dermatophytes can markedly be inhibited by a photochemical treatment with curcumin. This kind of photo-inactivation needs to be improved, however, because curcumin is poorly water-soluble. Therefore, a new water-soluble γ-cyclodextrin formulation of curcuminoids was tested for its photochemical inactivation of Trichophyton (T.) rubrum.

Materials and methods: Conidia were harvested from 6 typical strains of T rubrum and used to inoculate wells of microtiter plates. These wells were also filled with a γ-cyclodextrin curcuminoid formulation with 0.1% DMSO and Sabouraud broth. The assays were then irradiated with visible light (wavelength 420 nm, 45 J/cm² ). After 24 hours, curcuminoid was added once more, and irradiation was repeated. Fungal growth was monitored photometrically for 8 days and compared with controls.

Results: Growth of all 6 T rubrum strains was completely inhibited by the photochemical treatment with the γ-cyclodextrin formulation of curcuminoids. The same curcuminoid formulation applied without irradiation had only a minor inhibitory effect.

Discussion: Photo-inactivation of dermatophytes with a γ-cyclodextrin formulation of curcuminoids plus visible light is a very promising procedure with potential for a new treatment of patients with superficial tinea.

Keywords: conidia; dermatophytes; light; photo-inactivation; tinea.