Effect of Essential Oil of Ocimum gratissimum on the Trypanosomatid Herpetomonas samuelpessoai

In this study, we reported the effect of the essential oil of Ocimum gratissimum on Herpetomonas samuelpessoai, a nonpathogenic trypanosomatid. Parasites were grown at 28 or 37°C, in a chemically defined or a complex medium, containing essential oil obtained from Ocimum gratissimum. At concentrations from 20 to 250 μg/ml, the essential oil, progressively inhibited the protozoan growth. The IC50, in defined and complex media, at 28°C were 100 and 91 μg/ml, respectively. Cells cultivated in chemically defined medium were more sensitive to essential oil at concentration of 50, 62.5 and 100 μg/ml in relation to those cultured in complex medium at 37°C. In addition, ultrastructural and enzymatic alterations of the trypanosomatid were also evaluated. H. samuelpessoai exposed to 100 μg/ml of essential oil, in chemically defined medium at 28°C for 72 h, presented considerable ultrastructural alteration, mainly at mitochondrial level, as showed by transmission electron microscopy. Furthermore, cells cultivated in the presence of 100 μg/ml of essential oil showed a decrease of activity of the succinate cytochrome c reductase enzyme, a typical mitochondrion marker, as compared to untreated cells.