RESUMO
An essential oil was recently extracted from the leaves and flowers of yarrow (Achillea millefolium) and tested for in-vitro activity against Leishmania amazonensis and murine macrophages (i.e. the J774G8 cell line). The median inhibitory concentration (IC(50)) against L. amazonensis promastigotes was 7.8 µg/ml whereas the survival of amastigotes of this pathogen, within peritoneal murine macrophages, was halved by treatment with the oil at 6.5 µg/ml. The mean value for the median cytotoxic concentration of the oil, measured against adherent (uninfected) J774G8 macrophages, was 72.0 µg/ml (i.e. 9.2 and 11.0 times higher, respectively, than the IC(50) against the promastigotes and intracellular amastigotes). Scanning electron microscopy revealed that the oil caused morphological changes in the treated parasites, including alterations in their shape and size. In transmission electron microscopy, promastigotes treated with the oil (at the IC(50) of 7.8 µg/ml) showed various ultrastructural alterations, including changes in the flagellar membrane, abnormal membrane structures, rupture of the plasma membrane, atypical vacuoles, myelin-like figures, and vesicles that resembled autophagic vacuoles.
