Leishmaniasis is a neglected parasitic disease for which the conventional treatment can be considered inefficient and extremely aggressive, generating several and severe side effects. Therefore, the discovery of new drug candidates is important for the improvement in the quality of life of patients. Previously, we reported the promising results of isopentyl caffeate (ICaf) against Leishmania chagasi (agent of visceral leishmaniasis) and Leishmania amazonensis (agent of cutaneous leishmaniasis) promastigotes, displaying IC₅₀ of 1.56 and 1.71 μM, respectively. Herein, we aimed to decipher the mechanisms of anti-Leishmania action of ICaf. Light and scanning electron microscopy assays showed relevant morphological changes in promastigotes when treated with ICaf, including rounding of the parasite body, shortening of the flagellum, blebs on the plasma membrane and cellular aggregation. The parasite mitochondrion was targeted by ICaf, resulting in a significant reduction in its metabolic activity and electric membrane potential followed by an increase in the production of reactive oxygen species, which culminated in the loss of plasma membrane integrity and parasite death. Relevantly, ICaf also had a potent anti-amastigote action. The IC₅₀ values calculated for intracellular amastigotes of L. amazonensis were 3.27, 1.60 and 1.52 μM, while for L. chagasi the values were 2.48, 1.84 and 1.60 μM, respectively, after treating the infected macrophages with ICaf for 24, 48 and 72 h. ICaf was well tolerated by THP-1 macrophages, which gave rise to excellent selectivity indexes considering both Leishmania species. The current results suggest that ICaf may emerge as a chemotherapeutic alternative for the treatment of leishmaniasis.

利什曼病是一种被忽视的寄生虫病，常规治疗可被认为效率低下且极具侵袭性，会产生多种严重的副作用。因此，发现新的候选药物对于提高患者的生活质量具有重要意义。此前，我们报道了咖啡酸异戊酯 (ICaf) 对Leishmania chagasi（内脏利什曼病药物）和Leishmania amazonensis（皮肤利什曼病药物）前鞭毛体的良好结果，IC ₅₀分别为 1.56 和 1.71 μM。在这里，我们旨在破译反利什曼原虫的机制ICaf 的行动。光学和扫描电子显微镜分析显示，当用 ICaf 处理时，前鞭毛体的相关形态变化，包括寄生虫体变圆、鞭毛缩短、质膜上的气泡和细胞聚集。ICaf 靶向寄生虫线粒体，导致其代谢活性和膜电位显着降低，随后活性氧物质的产生增加，最终导致质膜完整性丧失和寄生虫死亡。相关地，ICaf 还具有有效的抗鞭毛虫作用。L. amazonensis细胞内无鞭毛体的 IC ₅₀值为 3.27、1.60和 1.52 μM，而L. chagasi在用 ICaf 处理感染的巨噬细胞 24、48 和 72 小时后，这些值分别为 2.48、1.84 和 1.60 μM。THP-1 巨噬细胞对 ICaf 有很好的耐受性，考虑到两种利什曼原虫，这产生了出色的选择性指数。目前的结果表明，ICaf 可能成为治疗利什曼病的化学治疗替代品。