Bahuaud D, Martinez-Ortiz de Montellano C, Chauveau S, Prevot F, Torres-Acosta F, Fouraste I, Hoste H
Unité Mixte de Recherche 1225 INRA/DGER, 23, Chemin des Capelles, 31076 Toulouse Cedex, France.
Parasitology. 2006 Apr;132(Pt 4):545-54. doi: 10.1017/S0031182005009509. Epub 2006 Jan 3.
The anthelmintic properties of tanniferous plants and of their secondary metabolites represent one possible alternative to chemotherapy that is currently being explored as a means of achieving sustainable control of gastrointestinal nematodes in ruminants. Previous in vivo and in vitro results suggest that tanniferous plants can have direct anti-parasitic effect against different stages of nematodes. However, the mode of action of the bioactive plant compounds remains obscure. The objectives of the current study were (1) to examine the hypothesis that extracts of tanniferous plants might interfere with the exsheathment of third-stage infective larvae (L3); (2) to assess the role of tannins in the process by examining the consequence of adding an inhibitor of tannins (polyethylene glycol: PEG) to extracts. The effects of 4 tanniferous plant extracts on exsheathment have been examined on L3 of Haemonchus contortus and Trichostrongylus colubriformis. Artificial exsheathment was induced in vitro by adding hypochloride solution to larval suspension. The evolution of exsheathment with time was measured by repeated observations at 10-min interval for 60 min. The selected plants were: genista (Sarothamnus scoparius), heather (Erica erigena), pine tree (Pinus sylvestris), and chestnut tree (Castanea sativa), with tannin contents ranging from 1.5 to 24.7% of DM. Extracts of a non-tanniferous plant (rye grass, tannin content: 0.3% of DM) were included in the assay as negative controls. The extracts were tested at the concentration of 600 microg/ml and the effects were compared to the rate of exsheathment of control larvae in PBS. No statistical differences in the pattern of exsheathment was observed after addition of rye grass or genista extracts for both nematode species and with heather extracts for T. colubriformis. In contrast, pine tree extracts on larvae of both species and heather extracts with H. contortus induced a significant delay in exsheathment. Last, contact with chest nut extracts led to a total inhibition of the process for both nematodes. These results suggest that extracts of tanniferous plants might affect a key process in the very early stages of larval invasion of the host. In most cases, the addition of PEG led to a total or partial restoration towards control values. This suggests that tannins are largely involved in the inhibitory process. However, other secondary metabolites may also interfere with the process that would help to explain some of the differences in response observed between the two nematode species.
含单宁植物及其次生代谢产物的驱虫特性是化疗的一种可能替代方法，目前正在探索将其作为实现反刍动物胃肠道线虫可持续控制的手段。先前的体内和体外研究结果表明，含单宁植物可能对不同阶段的线虫具有直接抗寄生虫作用。然而，生物活性植物化合物的作用模式仍不清楚。本研究的目的是：（1）检验含单宁植物提取物可能干扰第三期感染性幼虫（L3）脱鞘的假说；（2）通过研究向提取物中添加单宁抑制剂（聚乙二醇：PEG）的结果来评估单宁在该过程中的作用。已研究了4种含单宁植物提取物对捻转血矛线虫和蛇形毛圆线虫L3脱鞘的影响。通过向幼虫悬液中添加次氯酸盐溶液在体外诱导人工脱鞘。通过在60分钟内每隔10分钟重复观察来测量脱鞘随时间的变化。所选植物为：金雀花（帚石南）、石南花（欧石南）、松树（欧洲赤松）和栗树（欧洲栗），单宁含量占干物质的1.5%至24.7%。一种不含单宁植物（黑麦草，单宁含量：干物质的0.3%）的提取物作为阴性对照包含在试验中。提取物以600微克/毫升的浓度进行测试，并将结果与对照幼虫在磷酸盐缓冲盐水中的脱鞘率进行比较。对于两种线虫物种，添加黑麦草或金雀花提取物后，以及对于蛇形毛圆线虫添加石南花提取物后，脱鞘模式未观察到统计学差异。相比之下，松树提取物对两种线虫幼虫以及石南花提取物对捻转血矛线虫均导致脱鞘显著延迟。最后，与栗树提取物接触导致两种线虫的脱鞘过程完全受到抑制。这些结果表明，含单宁植物提取物可能在幼虫侵入宿主的非常早期阶段影响一个关键过程。在大多数情况下，添加PEG导致脱鞘率完全或部分恢复到对照值。这表明单宁在抑制过程中起主要作用。然而，其他次生代谢产物也可能干扰该过程，这有助于解释在两种线虫物种之间观察到的一些反应差异。
