Essential Oils from Croton Species: Chemical Composition, in vitro and in silico Antileishmanial Evaluation, Antioxidant and Cytotoxicity Activities

Chemotherapy treatment of leishmaniasis is based on the use of pentavalent antimonials, but these drugs present low efficacy and high toxicity. In the search for new antileishmanial agents, essential oils (EOs) from four Croton species (C. argyrophylloides, C. jacobinensis, C. nepetifolius and C. sincorensis) were evaluated against Leishmania infantum chagasi, L. amazonensis and L. braziliensis. EOs were analyzed by gas chromatography combined with mass spectrometry. Spathulenol, β-caryophyllene, β-caryophyllene oxide, 1,8-cineole and methyl eugenol were the major constituents. The evaluation of antioxidant activity by the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) method showed that all EOs have moderate antioxidant activity. All oils were similarly active against L. i. chagasi, and C. nepetifolius EO showed the best result against L. amazonensis, with median inhibitory concentrations (IC50) of 9.87 μg mL-1, similar to amphotericin B (IC50 = 7.38 μg mL-1). The oils presented low cytotoxicity in macrophages. The in silico analysis revealed that spathulenol and 1,8-cineole were active against the enzyme Leishmania infantum trypanothione reductase (LiTR), showing excellent interaction energies, making them promising agents for leishmaniasis control.

利什曼病的化疗目前以五价锑剂为主要治疗手段，但此类药物存在疗效欠佳、毒性较高的弊端。为筛选新型抗利什曼病活性制剂，本研究对4种巴豆属（Croton）植物的精油（essential oils, EOs）开展了抗利什曼原虫活性评价，受试原虫涵盖婴儿利什曼原虫恰加斯亚种（Leishmania infantum chagasi）、亚马逊利什曼原虫（L. amazonensis）与巴西利什曼原虫（L. braziliensis）。采用气相色谱-质谱联用（gas chromatography combined with mass spectrometry）技术对各精油的化学成分进行解析，鉴定得到的主要组分为斯巴醇（spathulenol）、β-石竹烯（β-caryophyllene）、β-石竹烯氧化物（β-caryophyllene oxide）、1,8-桉叶素（1,8-cineole）以及甲基丁香酚（methyl eugenol）。通过1,1-二苯基-2-苦基肼（1,1-diphenyl-2-picryl-hydrazyl, DPPH）法评估精油的抗氧化活性，结果显示所有受试精油均展现出中等强度的抗氧化能力。抗寄生虫活性评价结果表明，所有精油对婴儿利什曼原虫恰加斯亚种的抑制活性相近；其中，C. nepetifolius精油抗亚马逊利什曼原虫的活性最为优异，其半数抑制浓度（median inhibitory concentrations, IC50）为9.87 μg·mL⁻¹，与两性霉素B（IC50=7.38 μg·mL⁻¹）的抗虫活性相当。细胞毒性实验显示，各精油在巨噬细胞中仅表现出极低的细胞毒性。体外虚拟（in silico）分析表明，斯巴醇与1,8-桉叶素可靶向结合婴儿利什曼原虫锥硫氧还蛋白还原酶（Leishmania infantum trypanothione reductase, LiTR），二者与靶酶的结合能优异，具备开发为利什曼病防治候选药物的潜力。