The gastrointestinal nematodes (GIN) stand out as an important cause of disease in small ruminant, especially on goat farm. Widespread resistance to synthetic anthelminthics has stimulated the research for alternative strategies of parasite control, including the use of medicinal plants. The present work summarizes the in vitro and in vivo studies of plants with activity against GIN of goats, focusing on the description of chemical constituents related to this effect. This review retrieved 56 scientific articles from 2008 to 2018 describing more than 100 different plant species. The most frequently investigated family was Fabaceae (30.7%). Most in vitro studies on the activity of plant extracts and fractions were carried out with of free-living stages nematodes. In vivo studies were conducted mainly with the use of plants in animal feed and generally showed lower effectiveness compared to in vitro assays. The main plant secondary metabolites associated with anthelmintic effect are condensed tannins, saponin and flavonoids. However, the studies with compounds isolated from plants and elucidation of their mechanisms of action are scarce. Herbal medicines are thought to be promising sources for the development of effective anthelmintic agents.

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This study assessed the anthelmintic activity of plant-derived compounds against gastrointestinal nematodes of goats using the egg hatch and larval motility assays. The compounds tested were saponins (digitonin and aescin) and their respective sapogenins (aglycones), hecogenin acetate and flavonoids (catechin, hesperidin, isocordoin and a mixture of isocordoin and cordoin). Additionally, cytotoxicity of active substances was analysed on Vero cell through 3-4,5-dimethylthiazol-2-yl,2,5diphenyltetrazolium bromide (MTT) and propidium iodide (PI) tests. Significant reduction on the egg hatching (P 90%). Nevertheless, higher cytotoxicity was observed in the MTT assay, with IC50 of 0.20 mg mL-1 (aescin) and 0.0074 mg mL-1 (digitonin). Aescin and digitonin have a pronounced in vitro anthelmintic effect and the glycone portion of these saponins plays an important role in this activity.

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This study describes the effects of extracts and fractions of Persea willdenovii leaves against goat gastrointestinal nematodes and their cytotoxicity on Vero cells. The in vitro ovicidal and larvicidal activities of the crude ethanolic, hexane, ethyl acetate (EAE), butanolic and residual hydroethanolic extracts were assessed through the inhibition of egg hatching and larval motility assays. The most active extract (EAE) was then fractionated by chromatography in an open column containing silica gel, to furnish six fractions (Fr1-Fr6), which were also tested. The cytotoxicity of active extracts and fractions was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and trypan blue exclusion assay. The EAE and two fractions (Fr1 and Fr2) showed inhibitory activity in the egg hatching of gastrointestinal nematodes of goats in a concentration-dependent manner. The effective concentrations for 50% inhibition (EC50) of egg hatching were 2.3, 0.12 and 2.94 mg/ml for EAE, Fr1 and Fr2, respectively. All extracts and fractions were not effective in inhibiting 50% of motility of infective larvae. EAE and Fr2 had IC50 values (50% inhibitory concentration) of 4.95 and 2.66 mg/ml, respectively. Fr1 showed a slight cytotoxic effect (cellular inviability <30%) only after 48 h of treatment (MTT test). Gas chromatography-mass spectrometry (GC-MS) analysis showed the presence of six fatty acid ethyl esters, a fatty acid methyl ester and a long-chain ketone in the most active fraction. These constituents identified in P. willdenovii can be related to the high ovicidal activity and relatively non-toxic effect of the extracts.