Wangchuk Phurpa, Pearson Mark S, Giacomin Paul R, Becker Luke, Sotillo Javier, Pickering Darren, Smout Michael J, Loukas Alex
Centre for Biodiscovery and Molecular Development of Therapeutics, Queensland Tropical Health Alliance, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns Campus, Cairns, Australia.
PLoS Negl Trop Dis. 2016 Aug 4;10(8):e0004908. doi: 10.1371/journal.pntd.0004908. eCollection 2016 Aug.
Whipworms and blood flukes combined infect almost one billion people in developing countries. Only a handful of anthelmintic drugs are currently available to treat these infections effectively; there is therefore an urgent need for new generations of anthelmintic compounds. Medicinal plants have presented as a viable source of new parasiticides. Ajania nubigena, the Bhutanese daisy, has been used in Bhutanese traditional medicine for treating various diseases and our previous studies revealed that small molecules from this plant have antimalarial properties. Encouraged by these findings, we screened four major compounds isolated from A. nubigena for their anthelmintic properties.
METHODOLOGY/PRINCIPAL FINDINGS: Here we studied four major compounds derived from A. nubigena for their anthelmintic properties against the nematode whipworm Trichuris muris and the platyhelminth blood fluke Schistosoma mansoni using the xWORM assay technique. Of four compounds tested, two compounds-luteolin (3) and (3R,6R)-linalool oxide acetate (1)-showed dual anthelmintic activity against S. mansoni (IC50 range = 5.8-36.9 μg/mL) and T. muris (IC50 range = 9.7-20.4 μg/mL). Using scanning electron microscopy, we determined luteolin as the most efficacious compound against both parasites and additionally was found effective against the schistosomula, the infective stage of S. mansoni (IC50 = 13.3 μg/mL). Luteolin induced tegumental damage to S. mansoni and affected the cuticle, bacillary bands and bacillary glands of T. muris. Our in vivo assessment of luteolin (3) against T. muris infection at a single oral dosing of 100 mg/kg, despite being significantly (27.6%) better than the untreated control group, was markedly weaker than mebendazole (93.1%) in reducing the worm burden in mice.
CONCLUSIONS/SIGNIFICANCE: Among the four compounds tested, luteolin demonstrated the best broad-spectrum activity against two different helminths-T. muris and S. mansoni-and was effective against juvenile schistosomes, the stage that is refractory to the current gold standard drug, praziquantel. Medicinal chemistry optimisation including cytotoxicity analysis, analogue development and structure-activity relationship studies are warranted and could lead to the identification of more potent chemical entities for the control of parasitic helminths of humans and animals.
鞭虫和血吸虫在发展中国家联合感染了近10亿人。目前仅有少数几种驱虫药物可有效治疗这些感染；因此，迫切需要新一代的驱虫化合物。药用植物已成为新的杀寄生虫剂的可行来源。不丹雏菊Ajania nubigena已被用于不丹传统医学治疗各种疾病，我们之前的研究表明，该植物中的小分子具有抗疟特性。受这些发现的鼓舞，我们筛选了从A. nubigena中分离出的四种主要化合物的驱虫特性。
方法/主要发现：在这里，我们使用xWORM检测技术研究了从A. nubigena中提取的四种主要化合物对线虫鞭虫毛首鞭形线虫和扁形虫血吸虫曼氏血吸虫的驱虫特性。在测试的四种化合物中，两种化合物——木犀草素（3）和（3R,6R）-乙酸芳樟醇氧化物（1）——对曼氏血吸虫（IC50范围 = 5.8 - 36.9 μg/mL）和毛首鞭形线虫（IC50范围 = 9.7 - 20.4 μg/mL）表现出双重驱虫活性。通过扫描电子显微镜，我们确定木犀草素是对两种寄生虫最有效的化合物，此外还发现它对曼氏血吸虫的感染期童虫有效（IC50 = 13.3 μg/mL）。木犀草素导致曼氏血吸虫的体表损伤，并影响毛首鞭形线虫的角质层、杆菌带和杆菌腺。我们对木犀草素（3）以100 mg/kg的单次口服剂量对毛首鞭形线虫感染进行的体内评估，尽管比未治疗的对照组显著好（27.6%），但在减轻小鼠体内虫负荷方面明显弱于甲苯达唑（93.1%）。
结论/意义：在测试的四种化合物中，木犀草素对两种不同的蠕虫——毛首鞭形线虫和曼氏血吸虫——表现出最佳的广谱活性，并且对童虫有效，而童虫阶段对当前的金标准药物吡喹酮具有抗性。有必要进行包括细胞毒性分析、类似物开发和构效关系研究在内的药物化学优化，这可能会导致鉴定出更有效的化学实体来控制人和动物的寄生蠕虫。
