Laboratório de Parasitologia, Instituto Butantan, São Paulo, Brazil.
PLoS Negl Trop Dis. 2013 Jun 6;7(6):e2251. doi: 10.1371/journal.pntd.0002251. Print 2013.
Schistosomiasis is one of the most significant diseases in tropical countries and affects almost 200 million people worldwide. The application of molluscicides to eliminate the parasite's intermediate host, Biomphalaria glabrata, from infected water supplies is one strategy currently being used to control the disease. Previous studies have shown a potent molluscicidal activity of crude extracts from Piper species, with extracts from Piper tuberculatum being among the most active.
The molluscicidal activity of P. tuberculatum was monitored on methanolic extracts from different organs (roots, leaves, fruit and stems). The compounds responsible for the molluscicidal activity were identified using (1)H NMR and ESIMS data and multivariate analyses, including principal component analysis and partial least squares. These results indicated that the high molluscicidal activity displayed by root extracts (LC50 20.28 µg/ml) was due to the presence of piplartine, a well-known biologically-active amide. Piplartine was isolated from P. tuberculatum root extracts, and the molluscicidal activity of this compound on adults and embryos of B. glabrata was determined. The compound displayed potent activity against all developmental stages of B. glabrata. Next, the environmental toxicity of piplartine was evaluated using the microcrustacean Daphnia similis (LC50 7.32 µg/ml) and the fish Danio rerio (1.69 µg/ml). The toxicity to these organisms was less compared with the toxicity of niclosamide, a commercial molluscicide.
The development of a new, natural molluscicide is highly desirable, particularly because the commercially available molluscicide niclosamide is highly toxic to some organisms in the environment (LC50 0.25 µg/ml to D. similis and 0.12 µg/ml to D. rerio). Thus, piplartine is a potential candidate for a natural molluscicide that has been extracted from a tropical plant species and showed less toxic to environment.
血吸虫病是热带国家最严重的疾病之一，全球受影响人数近 2 亿。应用杀螺剂消除寄生虫中间宿主——光滑双脐螺，是目前用于控制该病的策略之一。此前的研究表明，胡椒属植物的粗提取物具有很强的杀螺活性，其中，菝葜提取物的活性最强。
用不同器官（根、叶、果和茎）的甲醇提取物监测菝葜的杀螺活性。利用（1）H NMR 和 ESIMS 数据以及多元分析，包括主成分分析和偏最小二乘分析，鉴定出负责杀螺活性的化合物。这些结果表明，根提取物（LC50 20.28μg/ml）具有高杀螺活性，原因是存在一种众所周知的生物活性酰胺——胡椒堿。胡椒堿从菝葜根提取物中分离出来，并测定了该化合物对光滑双脐螺成虫和胚胎的杀螺活性。该化合物对光滑双脐螺的所有发育阶段均表现出很强的活性。接下来，利用微甲壳类动物大型蚤（LC50 7.32μg/ml）和鱼类斑马鱼（LC50 1.69μg/ml）评估胡椒堿的环境毒性。与商业杀螺剂氯硝柳胺相比，该化合物对这些生物的毒性较低（LC50 0.25μg/ml 对大型蚤和 0.12μg/ml 对斑马鱼）。
开发一种新型天然杀螺剂是非常可取的，特别是因为市售杀螺剂氯硝柳胺对环境中的某些生物具有高毒性（LC50 0.25μg/ml 对大型蚤和 0.12μg/ml 对斑马鱼）。因此，胡椒堿是一种从热带植物中提取的潜在天然杀螺剂候选物，对环境的毒性较小。
