Detection of xanthomegnin in epidermal materials infected with Trichophyton rubrum

Xanthomegnin, a mutagenic mycotoxin best known as an agent of nephropathy a nd death in farm animals exposed to food-borne Penicillium and Aspergillus fungi, was first isolated about 35 y ago as a diffusing pigment from cultur es of the dermatophyte, Trichophyton megninii. This study investigates the production of xanthomegnin by the most common dermatophytic species, Tricho phyton rubrum, both in dermatologic nail specimens and in culture. In view of the labile nature of xanthomegnin, a chromatographic procedure was devel oped to allow high-performance liquid chromatography analysis within 1 h of sample extraction. In cultures, Tricho- phyton rubrum produced xanthomegni n as a major pigment that appears to give the culture its characteristic re d colony reverse. Xanthomegnin was also repeatedly extracted from human nai l and skin material infected by Trichophyton rubrum. The level of xanthomeg nin present, however, varied among the clinical samples studied. Xanthomegn in was not detected in uninfected nails. These results show that patients w ith Trichophyton rubrum infections may be exposed to xanthomegnin, although the consequences of such an exposure are not currently known.