First report of anti-Trichomonas vaginalis activity of the medicinal plant Polygala decumbens from the Brazilian semi-arid region, Caatinga.

Trichomonosis, caused by the flagellate protozoan Trichomonas vaginalis, is the most common non-viral sexually transmitted disease worldwide. Actually, the infection treatment is based on 5-nitroimidazole drugs. However, an emergent number of resistant isolates makes important the search for new therapeutic arsenal. In this sense, the investigation of plants and their metabolites is an interesting approach. In the present study, the anti-T. vaginalis activity of 44 aqueous extracts from 23 Caatinga plants used in folk medicine was evaluated. After screening 44 aqueous extracts from 23 distinct plants against two isolates from ATCC and four fresh clinical isolates, only the Polygala decumbens root extract was effective in reducing significantly the trophozoite viability. The MIC value against all isolates tested, including the metronidazole resistant, was 1.56 mg/mL. The kinetic growth assays showed that the extract was able to completely abolish the parasite density in the first hours of incubation, confirmed by microscopy. In summary, this study describes the first report on the activity of P. decumbens from Caatinga against T. vaginalis, being directly related to the popular knowledge and use.