Compounds Derived from the Bhutanese Daisy, <i>Ajania nubigena</i>, Demonstrate Dual Anthelmintic Activity against <i>Schistosoma mansoni</i> and <i>Trichuris muris</i>

Background 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.## 背景 鞭虫（Whipworm）与血吸虫（blood flukes）合计在发展中国家感染近10亿人口。当前可用于有效治疗此类感染的抗蠕虫药（anthelmintic drugs）寥寥无几，因此亟需开发新一代抗蠕虫化合物（anthelmintic compounds）。药用植物是新型驱虫剂（parasiticides）的可靠来源。不丹雏菊（Ajania nubigena）已被应用于不丹传统医学，用于治疗多种疾病；我们此前的研究发现，该植物中的小分子成分具有抗疟（antimalarial）活性。受上述发现鼓舞，我们对从A. nubigena中分离得到的4种主要化合物开展了抗蠕虫活性筛选。 ## 方法与主要发现 本研究采用xWORM检测技术（xWORM assay technique），评估了从A. nubigena中提取的4种主要化合物针对线虫（nematode）鼠鞭虫（Trichuris muris）以及扁形动物（platyhelminth）曼氏血吸虫（Schistosoma mansoni）的抗蠕虫活性。在所测试的4种化合物中，木犀草素（luteolin）与(3R,6R)-芳樟醇氧化物乙酸酯（(3R,6R)-linalool oxide acetate）对曼氏血吸虫和鼠鞭虫均表现出双重抗蠕虫活性：前者的半数抑制浓度（half maximal inhibitory concentration，IC50）范围为5.8~36.9 μg/mL，后者为9.7~20.4 μg/mL。 通过扫描电子显微镜（scanning electron microscopy）观察，我们确认木犀草素是对两种寄生虫均最为有效的化合物；此外，其对曼氏血吸虫的感染阶段——童虫（schistosomula）同样有效，半数抑制浓度为13.3 μg/mL。木犀草素可造成曼氏血吸虫的体被损伤，并影响鼠鞭虫的角质层、杆状带与杆状腺。我们以单次口服100 mg/kg的剂量，对木犀草素抗鼠鞭虫感染开展了体内评估：尽管其效果显著优于未给药对照组（蠕虫负荷降低27.6%），但在降低小鼠体内蠕虫负荷方面，其效果显著低于甲苯咪唑（mebendazole，蠕虫负荷降低93.1%）。 ## 结论与意义 在所测试的4种化合物中，木犀草素对两种不同的蠕虫——鼠鞭虫与曼氏血吸虫——表现出最优的广谱抗蠕虫活性，且对当前金标准药物吡喹酮（praziquantel）无法起效的血吸虫童虫阶段也具有活性。后续需开展包括细胞毒性分析、类似物开发以及构效关系（structure-activity relationship）研究在内的药物化学优化工作，有望发现更高效的化学实体，用于防控人类与动物的寄生蠕虫感染。