Inhibitory activity of Conyza bonariensis (L.) Cronquist tincture against fungi and bacteria causing superficial infections

Javier Esteban Mussin, Patricia Manzano, Magdalena Mangiaterra, Gustavo Giusiano

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Introduction: Conyza bonariensis (L.) Cronquist is a herbaceous plant of the underbrush group. It is distributed worldwide and is used to treat a variety of skin conditions.
Objective: Evaluate the in vitro inhibitory activity of the tincture from C. bonariensis leaves against fungi and bacteria causing superficial infections.
Methods: The tincture was obtained by alcoholic maceration of dry leaves of C. bonariensis. Minimum inhibitory concentration (MIC) of the tincture was determined against 53 isolates from patients with superficial lesions and 6 reference strains; 20 Malassezia (7 M. sympodialis, 7 M. furfur, 6 M. globosa), 16 Candida (8 C. albicans, 8 C. parapsilosis), 17 dermatophytes (6 Trichophyton rubrum, 6 Trichophyton mentagrophytes, 5 Microsporum canis) and 6 Staphylococcus aureus.
Results: A notable reduction in the viability of most of the microorganisms evaluated was obtained at low concentrations (under 10 % v/v) of the C. bonariensis tincture.
Conclusions: Results allow to conclude that the C. bonariensis tincture displays antibacterial activity against Staphylococcus aureus and antifungal activity against the main fungi causing superficial infections, such as dermatophytes, Candida and Malassezia. MIC variations were found between genera and species, but not within each species. These results may help experts find a scientific explanation for the empirical use of the C. bonariensis extract to treat various skin infections and revalue traditional ethnomedical knowledge.

Key words: Conyza bonariensis (L.) Cronquist, antifungal activity, antibacterial activity, skin infections.