Ultrastructural changes on clinical isolates of trichophyton rubrum, trichophyton mentagrophytes, and microsporum gypseum caused by solanum chrysotrichum saponin SC-2

Worldwide, dermatophytoses represent a high percentage of all superficial mycoses. The most frequently isolated dermatophyte is Trichophyton rubrum. Solanum chrysotrichum is a vegetal species widely used in Mexican traditional medicine to treat skin infections; its extract has been used to formulate an herbal medicinal product that is used successfully to treat tinea pedis. Spirostanic saponin SC-2 from S. chrysotrichum possesses high activity against dermatophytes. The present study reports the ultrastructural changes observed by means of transmission electron microscopy (TEM) in clinical isolates of T. rubrum, T. mentagrophytes, and Microsporum gypseum induced by saponin SC-2. Strains were grown in RPMI 1640 containing SC-2 (1600μg/mL). Fungi were harvested at 6, 12, 24, and 48h; controls without SC-2 were included. T. mentagrophytes was the most susceptible to the SC-2 saponin, followed by M.gypseum, while T. rubrum was the most resistant. The main alterations caused by the SC-2 saponin were as follows: i) loss of cytoplasmic membrane continuity; ii) organelle degradation; iii) to a lesser extent, irreversible damage to the fungal wall; and iv) cellular death.