Ultrastructure alterations induced by the essential oil from Croton cajucara in L. chagasi promastigotes. (A-B) Sections of untreated promastigote forms showing the main structures observed under transmission electron microscopy. (A) Normal flagellum (F) and flagellar pocket (FP) are observed in the anterior portion of the parasite. The nucleus (N) is round and the mitochondrion (M) is branched and observed along the parasite body, next to the cell surface (head arrows); (B) Detail of the mitochondrion containing the kinetoplast (K) with the array of DNA filaments (arrows); (C-H) Parasites treated for 5 (C-D), 15 (E-F), and 30 (G-H) min with 250 μg/mL of essential oil, showing different degrees of cell damage. (C) Parasite presenting dilated mitochondria (*) and condensed nuclear chromatin; (D) In the detail, the flagellar pocket showing intense release of vesicles (stars); (E) Increased mitochondrial volume and loss of cristae (*) and nuclear chromatin condensation (arrows); (F) Increased mitochondrial volume (*) and kDNA fragmentation (arrows) can be noted. (G-H) Parasites also exhibit dilated mitochondria (*), condensed nuclear chromatin, flagellar pocket (FP) with intense release of vesicles, and numerous vesicles in the cytoplasm.