Schistosoma mansoni: in vitro schistosomicidal activity of essential oil of Baccharis trimera (less) DC.

Schistosomiasis is a chronic parasitic disease caused by the trematode species Schistosoma mansoni. Chemotherapy is the only immediate recourse to minimize the prevalence and incidence of this disease worldwide. At present, praziquantel (PZQ) is the drug of choice for the treatment of all forms of schistosomiasis. However, dependence on a single drug is concern because some strains can become resistant. In this context, medicinal plants become potential candidates as sources of new drug prototypes. This study provides findings on the schistosomicidal activity of the essential oil of Baccharis trimera in in vitro assays. During the assays parameters such as motility of adult worms, oviposition, morphological changes on the tegument and especially the mortality rate of adult worms of the BH strain were evaluated. The assays, which were carried out with four concentrations - 24, 48, 91 and 130 μg/mL - of the essential oil, have shown a promising activity regarding the parameters under study. It was possible to notice a significant decline in the motility of the worms and a mortality rate of 100% 30 h after they had been exposed to the essential oil in the concentration of 130 μg/mL. Male worms were more susceptible, producing a dose-response effect within a smaller exposition period than female worms. In what refers to morphological changes, the essential oil of B. trimera induced a peeling on the tegument surface, as well as the destruction of tubercles and spines, which resulted in smooth areas on the body surface. The essential oil also caused tegument destruction in female worms, in addition to destruction of the oral and acetabular suckers. It is the first time that the schistosomicidal activity has been reported for essential oil of B. trimera (less) DC.