Mediterranean shrub extract shows promise against ringworm fungi

Transmission electron microscopy images of the dermatophytes T. rubrum (A–F) and M. canis (G–L). The images show untreated cells (A, B, G, H) and cells treated with C. salviifolius extract (C–F, I–L), showing alterations in cellular structure. Arrows indicate autophagy-like structures. Source: Álvarez-Martínez et al., Journal of Ethnopharmacology. Image by Álvarez-Martínez et al., Journal of Ethnopharmacology. / UMH

Researchers in Spain, Belgium, and Portugal report that an extract of the rockrose plant, Cistus salviifolius, kills several of the fungi responsible for superficial infections of the skin, hair, and nails.

The study, led by scientists at Miguel Hernández University of Elche with colleagues at the universities of Namur and Coimbra, was published in the Journal of Ethnopharmacology. For generations, people around the Mediterranean have applied preparations of the hardy, sun-loving rockrose to wounds, inflamed skin, and infections, a fact that interested the researchers.

"Traditional medicine provides us with clues, but we need to experimentally determine what lies behind these uses, what biological processes are actually taking place and under what conditions they may be useful," said Dr. Vicente Micol Molina in a press release. Dr. Molina is a researcher at the University of Elche’s Institute for Research in Biotechnology and Health.

Using broth microdilution assays under EUCAST guidelines, the team found selective fungicidal activity against dermatophytes, with minimum inhibitory concentrations of 78 mg/L against Trichophyton rubrum and Microsporum canis. The extract, composed mainly of tannins and flavonoids, showed no activity against Candida albicans at the concentrations tested.

Transmission electron microscopy revealed extensive vacuolization, membrane detachment, and cytoplasmic disorganization, suggesting the extract disrupts several cellular processes at once. However, which compounds drive the effect remains unknown.

"We observed that the fungus stops growing and that its cells sustain substantial damage. This helps us understand why the rockrose extract has fungicidal activity and allows us to begin investigating the specific mechanisms involved," said Dr. Francisco Javier Álvarez Martínez, the study's first author.

In dermatophyte-infected reconstructed human epidermis, topical treatment after infection reduced fungal burden and tissue invasion, preserved barrier integrity as measured by transepithelial electrical resistance, and attenuated IL-1α and IL-8 release, particularly against T. rubrum. Keratinocyte viability was not reduced.

"This means that, in this model and at the concentrations used, the extract showed no toxicity to the main cells of the epidermis. This is an important result, although it is still not enough to say that it is safe as a treatment in humans," the researchers cautioned.

The extract also showed strong antioxidant activity and significantly inhibited collagenase, elastase, and hyaluronidase. The authors see potential for development of creams or hydrogels, but do not endorse applying the plant directly to skin. Next steps include testing against resistant strains, formulation work, animal studies and, eventually, clinical trials.