Instituto de Producción Animal, Facultad de Agronomía, Universidad Central de Venezuela, Maracay, Edo. Aragua, Venezuela.
Vet Parasitol. 2012 May 25;186(3-4):390-8. doi: 10.1016/j.vetpar.2011.11.004. Epub 2011 Nov 7.
Lectins are plant secondary metabolites (PSM) found in many forages and which may confer anthelmintic properties to gastrointestinal parasites through disrupting the development of parasitic larvae throughout its life cycle. In experiment 1, the ability of the plant lectins jacalin (JAC), concanavalin A (Con A), phytohemagglutinin E2L2 (PHA-E2L2), phytohemagglutinin L4 (PHA-L4), phytohemagglutinin E3L (PHA-E3L), kidney bean albumin (KBA), Robinia pseudoacacia agglutinin (RPA), Maackia amurensis lectin (MAA), Maclura pomifera agglutinin (MAA), Dolichos biflorus agglutinin (DBA), wheat germ agglutinin (WGA) and Galanthus nivalis agglutinin (GNA) to disrupt the feeding of the first stage larvae (L(1)) of the sheep gastro-intestinal nematodes (GIN) Teladorsagia circumcincta, Haemonchus contortus and Trichostrongylus colubriformis was investigated using a larval feeding inhibition test (LFIT). Only PHA-E3L, WGA and Con A had a potent effect on disrupting larval feeding of all of the three species of GIN investigated. The lectin concentration required to inhibit feeding in 50% of L(1) (IC50) was 7.3±1.2, 8.3±1.4 and 4.3±1.7 μg/ml for PHA-E3L; 59.1±32.4, 58.7±11.9 and 8.1±7.0 μg/ml for Con A and 78.9±11.2, 69.4±8.1 and 28.0±14.1 μg/ml for WGA for T. circumcincta, H. contortus and T. colubriformis larvae, respectively (P=0.006). The addition of the lectin inhibitors fetuin, glucose/mannose or N-acetylglucosamine for PHA-E3L, Con A and WGA, respectively, caused an increase in the proportion of larvae that had fed at all concentrations for PHA-E3L only. In experiment 2, the effect of extracts from the tropical plants Azadiractha indica, Trichanthera gigantea, Morus alba, Gliricidia sepium and Leucaena leucocephala on the feeding behaviour of H. contortus L(1,) was examined. A. indica, T. gigantea and M. alba failed to inhibit 50% of larvae from feeding at concentrations up to 10mg plant extract per ml. In contrast, both G. sepium and L. leucocephala demonstrated a dose-dependent effect on larval feeding with respective IC50 estimates (mean±s.e.) of 0.015 mg/ml ±0.001 and 3.465 mg/ml ±0.144, effects which were partly reversed by the inclusion of either the tannin inhibitor polyethylene glycol or the lectin inhibitor Fetuin. These studies demonstrate that plant lectins can have an inhibitory effect on the feeding behaviour of first stage larvae of ovine GIN in vitro. Moreover they also provide novel evidence that lectins may contribute to the anthelmintic properties of some tropical forage plant extracts, such as G. sepium and L. leucocephala.
凝集素是植物次生代谢物（PSM），存在于许多饲料中，通过破坏寄生虫幼虫整个生命周期的发育，可能为胃肠道寄生虫提供驱虫特性。在实验 1 中，植物凝集素 Jacalin（JAC）、伴刀豆球蛋白 A（Con A）、植物血球凝集素 E2L2（PHA-E2L2）、植物血球凝集素 L4（PHA-L4）、植物血球凝集素 E3L（PHA-E3L）、菜豆白蛋白（KBA）、刺桐凝集素（RPA）、黄莲凝集素（MAA）、麻疯树凝集素（MAA）、多花胡枝子凝集素（DBA）、麦胚凝集素（WGA）和雪花凝集素（GNA）破坏绵羊胃肠道线虫（GIN）的第一阶段幼虫（L（1））摄食的能力使用幼虫摄食抑制试验（LFIT）进行了研究。只有 PHA-E3L、WGA 和 Con A 对三种研究的 GIN 幼虫的摄食具有强烈的抑制作用。抑制 50%的 L（1）摄食的凝集素浓度（IC50）分别为 PHA-E3L 为 7.3±1.2、8.3±1.4 和 4.3±1.7 μg/ml；Con A 为 59.1±32.4、58.7±11.9 和 8.1±7.0 μg/ml；WGA 为 78.9±11.2、69.4±8.1 和 28.0±14.1 μg/ml，用于 T. circumcincta、H. contortus 和 T. colubriformis 幼虫（P=0.006）。对于 PHA-E3L、Con A 和 WGA，分别添加凝集素抑制剂胎球蛋白、葡萄糖/甘露糖或 N-乙酰葡萄糖胺，导致仅在所有浓度下喂食的幼虫比例增加。在实验 2 中，研究了热带植物印楝、巨藻、桑、银合欢和银叶相思树提取物对弯曲食道线虫 L（1）摄食行为的影响。A. indica、T. gigantea 和 M. alba 未能抑制高达 10mg 植物提取物/ml 的幼虫 50%摄食。相比之下，金合欢和银叶相思树都对幼虫摄食表现出剂量依赖性效应，相应的 IC50 估计值（均值±s.e.）分别为 0.015 mg/ml ±0.001 和 3.465 mg/ml ±0.144，这些效应部分被单宁抑制剂聚乙二醇或凝集素抑制剂胎球蛋白逆转。这些研究表明，植物凝集素可以在体外抑制绵羊 GIN 第一阶段幼虫的摄食行为。此外，它们还提供了新的证据表明，凝集素可能有助于一些热带饲料植物提取物的驱虫特性，例如银合欢和银叶相思树。
